Mapping Francis Younghusband in the Gobi Desert, 1887, Part 4: from the Ya-hu oasis to Hami.

[Back to Part 3: from the Hun-kua-ling sandhills to the Ya-hu oasis]

From Ya-Hu to Hami, we can see that Younghusband now has to turn south, as his own map shows.

The journey takes from June 23rd to July 4th, or twelve days. His mapmaker places Ula Khutun almost halfway from Ya-hu to Hami, but I think this is likely wrong, as Younghusband tells us he arrives in Ula Khutun only two days after reaching Ya-hu.

On June 25 we reached Ula-khutun, where the road to Hami leaves the road to Guchen. It is merely a camping-ground, situated in a stony plain, surrounded by low mounds or heaps of gravel, at the southern base of a branch from the main range of the Altai Mountains, from which it is separated by a gravelly plain about twenty miles in width—the extension westward of the same plain in which Ya-hu is situated. The height of this southern ridge must be considerable, for a heavy snowstorm was falling on it even so late in the year as this (June 25), and the snow seemed to remain there.

(p. 111)

After Ula Khutun, Younghusband reports one more day of travel through “low hills” before they begin the arduous crossing of the “desert of Zungaria” on the 27th. For these reasons (plus the fact that Younghusband says Ula Khutun is in a westward extension of the same plain as Ya-hu is in) I think it makes sense to provisionally place Ula Khutun as shown below. The only additional evidence for this (there is nothing on any map I have found that contains anything remotely like the word “Khutun”) is that what I have shown as the route to Guchen is also the present day road.

Younghusband gives no indication of what route he took from Ya-hu to Ula Khutun, so that must be regarded as hypothetical as well.

On the days of June 27–29, Younghusband gives us an uncharacteristically long paragraph describing crossing the desert of Zungaria. I have added emphasis to certain phrases within the quote to highlight the important landmarks.

Our next march, however, was the most trying of all, for we had to cross the branch of the Gobi which is called the desert of Zungaria, one of the most absolutely sterile parts of the whole Gobi. We started at eleven in the morning, passing at first through the low hills, which were perfectly barren, but the hollows had a few tufts of bushes, and one hollow was filled with white roses. After seven and a half miles we left the hills, and entered a gravel plain covered with coarse bushes, but no grass. There was no path, and we headed straight for the end of the Tian-shan range. After passing over the plain for fifteen miles, we struck a path and followed it along till 1.3o p.m., when we halted to cook some food and rest the camels. It was of no use pitching camp, for there was neither water, fuel, nor grass ; not a bush, nor a plant, nor a blade of grass—absolutely nothing but gravel. I lay down on the ground and slept till Liu-san brought me some soup and tinned beef. We started again [June 28th] at 4 a.m., and marched till 3.15 p.m. through the most desolate country I have ever seen. Nothing we have passed hitherto can compare with it —a succession of gravel ranges without any sign of life, animal or vegetable, and not a drop of water. We were gradually descending to a very low level, the sun was getting higher and higher, and the wind hotter and hotter, until I shrank from it as from the blast of a furnace. Only the hot winds of the Punjab can be likened to it. Fortunately we still had some water in the casks, brought from our last camping-ground, and we had some bread, so we were not on our last legs; but it was a trying enough march for the men, and much more so for the camels, for they had nothing to eat or drink, and the heat both days was extreme. We at last reached a well among some trees. The guide called the distance two hundred and thirty li, and I reckon it at about seventy miles. We were twenty-seven hours and three-quarters from camp, including the halt of four and a half hours. We had descended nearly four thousand feet, and the heat down here was very much greater than we had yet experienced. We were encamped on the dry bed of a river, on the skirts of what looked like a regular park—the country being covered with trees, and the ground with long coarse grass. It was most striking, as on the other bank of the river there was not a vestige of vegetation.

(pp. 113-114)

Although the region of Dzungaria (Younghusband’s “Zungaria”) is 350 miles to the northwest, Soviet topographic maps agree in calling the arid basin between the Altai mountains and the extreme east end of the Tian Shan the the “Dzungarian Gobi” (Джунгарская гоби).

“Gobi,” is discussed by Owen Lattimore in a 1973 article as the Mongolian term for “a land of thin herbage, more suitable for camels than for cows, but capable also, if herds are kept small and moved frequently, of sustaining horses, sheep, and goats.” However Younghusband’s repeated emphasis on the barrenness of the area (“absolutely sterile,” “the most desolate country I have ever seen,” “neither water, fuel, nor grass; not a bush, nor a plant, nor a blade of grass—absolutely nothing but gravel”) indicates what a formidable crossing this is. The DEM shows it as essentially a big hole, with the very eastern end of the Tian Shan on the south side.

Incidentally, one doesn’t usually find the mountains adjacent to Hami labelled as being part of the Tian Shan. The Tian Shan (sometimes written Tien Shan) are a major range of central Asia, but the name is usually found running just from Kyrgyzstan (on the west end) to the Turfan Depression (on the east end).

However, occasionally you do find a map extending the Tian Shan all the way to Hami, which is clearly how Younghusband sees it.

Now, we don’t know exactly where the party entered the Dzungarian Gobi, but we do know that after fifteen miles of heading “straight for the end of the Tian-shan range” they struck a path, which then presumably led them in a less straight line to the next landmark: a well, among trees, 4000 feet lower (1200 metres) than where they started. It is now the afternoon of June 28th.

It’s a fair bet that the elevation of the place they left the hills on the 27th was close to 1500 metres elevation, as shown by the map below. The lowest area in the Dzungarian Gobi is at about 400 metres, so this roughly agrees with Younghusband’s “We had descended nearly four thousand feet.”

Today there is a settlement in the bottom of this arid depression named Naomaohu. In satellite imagery it really jumps out in this desert because of its green fields, which presumably rely on extensive irrigation from pumped groundwater. Yet outside of town, here in the bottom of the basin there are not only scattered trees occurring naturally, but also, Google tells us, the “Yiwu Naomaohu Populus Forest Ecological Garden Scenic Area (伊吾淖毛湖胡杨林生态园景区).” Populus is the genus of cottonwoods and aspen, and the special designation as a scenic area suggests that trees are, well, special in this area.

But, to be fair, the extent of trees in this bottomland goes on for some distance, so we can’t know exactly where the party spent the night of the 28th.

From here, on June 29th, they begin to ascend and pass by a remarkable house.

…we had to start at 1:30 in the afternoon, and march till three the next morning.

For nearly two miles we passed through a country well covered with trees, and patches of coarse grass and bushes. The soil was partly clay and partly sand. This ended as suddenly as it had begun, and we passed over the gravel desert again, where there was no vestige of grass or scrub. The hot wind blowing off this seemed absolutely to scorch one up; but yesterday’s order of things were now reversed—we were ascending while the sun was descending, and it gradually became cooler. About ten at night we suddenly found ourselves going over turf, with bushes and trees on either side, and a shrill clear voice hailed us from the distance. We halted, and the guide answered, and the stranger came up and turned out to be a Turki woman, who led us through the bushes over some cultivated ground to a house, the first I had seen for nearly a thousand miles… Flowing by the house was a little stream of the most delicious water. It was scarcely a yard broad, but it was not a mere trickle like the others we had passed in the Gobi, but was flowing rapidly, with a delightful gurgling noise, and was deep enough for me to scoop up water between my two hands.

(p. 116)

This water occurs only here, however, and it is two more hours across gravel to a distinctive gorge.

…hardly fifty yards from the stream the vegetation disappeared, and we were again on gravel desert, and we had still to travel for five hours, gradually ascending as before—at twelve passing through a gorge two and a half miles long, in a range of little hills running parallel to the slope. We halted as the day was dawning, on a part of the slope where there was enough scrub for fuel and for the animals to eat. No water.

(pp. 116-117)

At dawn on June 30th they are about three hours beyond the gorge.

There’s only one “gorge two and a half miles long, in a range of little hills running parallel to the slope.” Today the the road from Naomaohu to Hami goes through it.

The house with the trickling stream that they encountered two hours before the gorge should be, given their typical rate of travel, about four miles before it. There are several candidates of small, isolated areas with intense vegetation growth in the middle of the gravel plain that leads up towards the gorge. These can be seen on images taken by the Sentinel-2 satellite, using its “NDVI” band combination, which causes vegetation to jump out as green.

The leftmost site appears to be irrigated by a ditch coming from the gorge, so it perhaps did not exist in 1887. The centre and rightmost sites both have many trees and are equally good candidates. The dotted red line indicates possible travel from the present-day site of Naomaohu, but Younghusband’s party could easily have crossed the bottom of the depression further east, putting these sites on a line with the mouth of the gorge.

On June 30th they continue to somewhere called Morgai.

Next day we continued to ascend the long lower slopes of the Tian-shan, gradually rounding the eastern extremity of these mountains. We passed a cart-track leading from Barkul to Hami, which makes this detour round the Tian-shan to avoid crossing them. The going was bad on account of the stones, and because the whole slope was cut up by dry watercourses. These were seldom more than a foot deep, but the slope was covered with them. They were formed by the natural drainage from the mountains, which, instead of running in deep valleys, spreads over the slope. The whole country was still barren, being covered with scrub only; but in the depression at the foot of the slope was a small Turki village, surrounded with trees and cultivation.

That night we encamped near a Turki house called Morgai, surrounded with fields of wheat and rice, watered from a small stream which appeared above the surface just here, and which, lower down, spread out and was swallowed in the pebbly slopes of the mountain.

(p. 117)

The pass that they will cross the next day to Ching-cheng is fairly obvious (again, a road runs through it today), so we can feel pretty confident that on this day they work their way southeast and across the slope to the northern end of the pass. They would not gain much elevation as they traverse to the top of the debris fan issuing from the mountains.

Google Hybrid shows a small settlement bearing the Chinese name of Shangmaya at this site, but the Soviet 1:500,000 scale map from 1985 (K-46-2) shows “разв. Могой [razv. Mogoi], meaning “the развалины [razvaliny]” i.e., ruins “of Mogoi.” This, I think we can feel fairly confident, is Morgai.

The next day, July 1st, they cross the east end of the Tian-shan.

Starting early, we ascended the stream, but it soon disappeared again, and we saw nothing more of it. The hillsides were at first rather bare, but the higher we got the greener they became; and after five or six miles were covered with rich green turf, most delightful to look upon after the bare hills of the Gobi; while here and there through an opening in the hills we could catch a glimpse of the snowy peaks above. There are, however, no trees nor even bushes, either on the hills or in the valleys…
We crossed the range at a height of eight thousand feet [2400 m]. Except the last half-mile the ascent was not steep, but led gradually up a narrow valley. The last mile or two was over soft green turf, and near the summit there was a perfect mass of flowers, chiefly forget-me-nots; and I am sure I shall not forget for a very long time the pleasure it was, seeing all this rich profusion of flowers and grass, in place of those dreary gravel slopes of the Gobi Desert.

…a curious characteristic of these hills is that there is absolutely no water. For twelve miles from Morgai to the summit of the pass we had not seen a drop of water… Five miles on the southern side a small stream appeared, and the valley bottom was partitioned off into fields, round which irrigation ducts had been led ; but these were all now deserted, and the water was wasted in flowing over uncultivated fields. Trees now began to appear near the stream, and at 11:10 p.m. we pitched camp on a little grassy plot near a stream of cold clear water, and under a small grove of trees.

(pp. 119-120)

The pass (summit elevation 2580 metres, or 8450 feet) is just twelve miles of ascent from Morgai. Five miles down on the south side, water indeed appears, in the form of irrigated fields today.

The next day is July 2nd, and the presence of “July 22” in the text is surely a misprint.

On July 22 we passed a small square-walled town called Ching-cheng, surrounded by fields of wheat and some good grass land, but when these ended the desert began again directly.

(p. 121)

Ching-cheng is easy to locate even on Google Terrain, where it shows up as Qinchengxiang. (Xiang is a Chinese word for township.)

A long way off over the desert we could see a couple of poplar trees rising out of the plain. These poplars are very common all over Chinese Turkestan, and they make excellent landmarks. We reached these at twelve at night, and found a few soldiers stationed there, who said that Hami was still a long way off. Now, as my constant inquiry for the last month had been, ” How far are we from Hami?” and as the guide for the last few days had each time said we were only sixty miles off, I was rather exasperated to find that, instead of having ten or twenty miles more to get over, there was still a good fifty.

(p. 121)

Consequently in the map above I have placed them, at the end of July 2nd at a line of poplars, fifty miles out of Hami.

Two days later it is not entirely with good grace that Younghusband reaches the end of the first leg of his journey.

So on striking camp at two the following afternoon [July 3rd], I told my men that my tent would not be pitched again till Hami was reached, so they had better prepare themselves for a good march. We travelled on all through the afternoon—a particularly hot one; then the sun set before us, and still we went on and on through the night till it rose again behind us.

We halted for a couple of hours by the roadside to ease the camels, and then set out again. At eight o’clock [July 4th] the desert ended, and we began to pass through cultivated land, and at last we saw Hami in the distance, and after traversing a tract of country covered with more ruined than inhabited houses, we reached an inn at 11 a.m., and it was with unspeakable relief that I dismounted from my camel for the last time.

(pp. 121-122)

To wrap up, let’s look now at the full route from Peking to Hami.

A solid line on this map indicates the portions of the route I’m confident about, and a dotted line indicates the parts that seem right but we can’t really be sure.

This would be a very interesting route to re-create today, although the way it crosses from China into Mongolia and back at remote places might make it politically challenging to do so.

If you’ve enjoyed this piece of research, you may want to download a KML file of various points along Younghusband’s route that I have mentioned in these posts. It contains a tour that you can play in Google Earth to “fly” along the route.

There is also a KML of the route itself. I recommend viewing these with vertical exaggeration set to “3” on the 3D View tab of Google Earth’s Options.

Mapping Francis Younghusband in the Gobi Desert, 1887, Part 3: Hun-kua-ling sandhills to Ya-hu oasis

[Go back to Part 2: From the Galpin Gobi to the Hun-kua-ling sandhills.]

From here to the Ya-hu oasis (which Younghusband reaches on June 23rd) the route is obscure, and we find old maps less useful. We have to rely more upon comparing his route description with images of the landscape. Let’s work backwards from Ya-hu, which he describes quite precisely.

The name of this oasis is Ya-hu. It is about five miles in extent from west to east, and rather more from north to south. Some twelve miles to the west is a remarkable hill, called by the guide Ho-ya-shan. It rises very abruptly out of the plain to a height of about two thousand feet, and is a perfectly solid mass of rock of a light colour.

(p. 111)

Satellite imagery reveals an area of outcropping surface water of about the right dimensions some 300 miles to the northwest of the Hun-kua-ling sandhills. Geonames.org identifies a populated place there called Dzahuy, for which Ya-hu is a reasonable misunderstanding, and Google Terrain has a community about 10 km away called Zakhui, more or less where the Soviet map L-47-3 places a settlement labelled Бригада Дзахуйн [Brigada Dzakhuyn]. There is a distinctive peak to the west, which geonames calls Hatan Hayrhan, the Soviets labelled as Хатин-Хайрхан [Khatin-Khayrkhan] and Google Terrain calls Eej Khairkhan.

You can see Ho-ya-shan, rising “abruptly out of the plain,” quite well in Google Earth.

We can feel confident about the location of the Ya-hu oasis, but how does Younghusband get here over the next fifteen days? Looking at the DEM, the route appears straightforward.

However, there are a few indications that he might not have taken this shortest, lowest route. One is that, about a third of the way along, Younghusband describes himself as going “west-by-south,” which the shortest, lowest route route doesn’t really do. Another is that the Soviet topographic maps don’t show tracks or trails (which they are usually quite thorough about) along the route of travel in the eastern half this corridor. Finally, Younghusband’s own map, in this section, shows him continuing northwest after the Hun-kua-ling, and passing north of a range of mountains as he visits “Man-chin-tol” and “Liang-ko-ba,” before returning to the big valley that leads to Ya-hu.

I would propose the following route, suggested by Younghusband’s map, but also supported by landscape features he describes along the way.

Let’s start on the day he leaves the end of the Hun-kua-ling, probably on June 8th.

After passing the end of the sand-range, we entered a country different from any we had yet gone through. In origin it was probably a plain of sand, but the wind’s action has broken it up into sandhills and depressions, making up a scene which, for its extreme wildness and desolation, surpasses anything I have ever seen.

(p. 98)

There is just such terrain off the west end of the sand dunes, as shown in a Google Earth view looking back southeast at the Hun-kua-ling.

On the travel day of June 9th…

an hour later reached the dry bed of a river flowing south, one hundred feet below the camp, and the lowest point I have yet reached in the Gobi (probably two thousand eight hundred feet).

(p. 102)

No place in the local area is actually this low (853 metres) but there is a distinctive dry riverbed running south at an elevation of 1045 metres with low hills before and after it. (see below in Google Earth looking northwest.)

Two days later they come to a large encampment…

on the 11th we reached a large Mongol encampment named Man-chin-tol, in a plain at the foot of the first spurs of the Altai Mountains… Water was plentiful, being found in small pools all over the plain. It had, however, a brackish taste, and there was soda efflorescence on the margin of the pools.

(p. 103)

It is hard to say which hills Younghusband would have meant by the “first spurs” of the Altai, and there is nothing like “Man-chin-tol” on any map I have found. However, the oasis of Hatansuudal (called Khatansuudal / Хатансуудал on Google Terrain) is in roughly the right place, provides surface water and is in a plain abutting some spurs of the Altai. The same can be said of the wet area about ten miles southeast of it. Here are both sites, looking west in Google Earth.

Incidentally, Google Translate tells us that tal (тал) is the Mongolian word for valley.

On June 13th (two more days later) Younghusband gives some specific observations on distances to landmarks, as well as his direction of travel…

To the north, at a distance of twenty-five miles, are the Altai Mountains, rising to about nine thousand feet above the sea. …We started at 3.45, and passed over a gravel plain in a west-by-south direction. This plain is bounded on the south by a range at a distance of about eight miles. The range runs in a general easterly by westerly direction, and is about six hundred feet high on the average.

(pp. 105-6)

These distances (25 miles north, 8 miles south) are generally true along the entire trek going west-southwest from Hatansuudal, if we assume that by “the Altai Mountains” he here means the mass of Tergun Bogd, which at 3900 metres (almost 13,000 feet) is the highest peak in the Altai Mountains; and by the range that “runs in a general easterly by westerly direction” he means the distinctive, dark-coloured ridge which rises to 2086 metres (= 6800 feet) south of his presumed route.

At the end of the day on the 14th …

We camped at 11.35 at Liang-ko-ba, a collection of four Mongol yurts on the plain, round a patch of green.

(p. 107)

I cannot find a specific place called Liang-ko-ba, so we must assume he is continuing west, paralleling the main chain of the Altai

On the 15th…

We started at 4:40, and still passed over gravelly plain, keeping along the edge of a low range of hills parallel to the road on the right.

(p. 107)

A low range of hills does occur roughly where we would expect Younghusband to be at this point, although to be fair there are many such low ranges of hills in the area.

Finally, on the morning of the 16th Younghusband climbs a hill and gives us measurements of features he sees, with specific bearings to them.

In the morning I climbed a hill and had a fine view of the country round for about eighty miles in every direction. The main range of the Altai Mountains is not at all of a uniform height, but, on the contrary, consists of distinct high ridges connected by lower hills. To the eastward I could see the snow-capped ridge which forms the butt end of the Altai Mountains. It is about twenty-five miles in length, and north-west of it is a second ridge, which also had some slight snow on it. In the space between the two ridges—fifty or sixty miles—is a succession of lower hills, rising about one thousand feet above the plain. The two ridges rise abrupt and clear from the surrounding hills. Between my route and the Altai Mountains is a succession of low, narrow ridges with intervening plains running in a southeasterly direction. … To the south the same succession of ridges and plains extends. The ridges are from three hundred to five hundred feet in height, and five or six miles apart.

(pp. 107-8)

We should be able to figure out where Younghusband was standing, and there are two locations that fit the description.

The “butt end of the Altai Mountains,” with the “second ridge” to its northwest, can only be Tergun Bogd (which is indeed 25 miles long) and Bayan Tsagan Nuru. The two are indeed separated by fifty miles, and connected by a “succession of lower hills.” If we take Younghusband’s bearing of “to the eastward” literally, then he needs to be at the point above labelled “Best viewpoint suggested by bearings,” a place where Tergun Bodg is truly east of him. To have come this far north, however, he would have travelled much closer to Tergun Bogd than the 25 miles he reported on the 13th. The other point, (“Best viewpoint suggested by route so far”) seems like a reasonable alternative.

His other observation, that between him and the Altai Mountains are a “succession of low, narrow ridges with intervening plains running in a southeasterly direction” suggests this second location as well.

During travel that day…

… we followed down the gravelly bed of a stream which appeared occasionally in a small trickle above the surface, and the margin of which was covered thickly with the soda efflorescence which seems invariably to mark the presence of water in the Gobi.

(p. 108)

And then…

On the 17th we emerged from the hills again, on to another great plain running between two parallel ranges of bare hills.

(p. 108)

There are many possible candidates for the “gravelly bed of a stream,” but there is one major one that could bring the party out into the large plain to the south.

From here the travel to Ya-hu is straight northwest along this plain.

They lose a day of travel due to mud, and on June 20th Younghusband notes the heights of the ranges on either side.

We started the next morning, and for a few days continued along the plain between the two parallel ranges, that to the north rising some one thousand five hundred feet [450 metres], and the one to the south about eight hundred feet [250 metres] above the plain.

(p. 109)

The area where I place Younghusband agrees with this observation in that the southern range is lower than the northern, but it does not agree with his estimates of height, the northern range actually being closer to 800 metres above the plain and the southern 400 metres.

Comparing this with Younghusband’s estimate of the elevation of Tergun Bogd a few days earlier, it seems fair to observe that he is consistently underestimating the height of features. This is hardly surprising for a 24-year-old in an unfamiliar environment; and indeed approaching the Hurku Hills, he wrote, “We can realize how deceptive the distances are here. Some days ago we first saw this range, and I thought that we should reach it at the end of that march, but we have taken four days to do so.”

On the 23rd they arrive at the Ya-hu oasis, as quoted at the top of this page.

Go on to Part 4: from the Ya-hu oasis to Hami.

Mapping Francis Younghusband in the Gobi Desert, 1887, Part 2: Galpin Gobi to Hun-kua-ling sandhills

[Go back to Part 1: Kwei-hwa-cheng to Galpin Gobi]

On the 13th we passed through some low hills, and then descended a valley in which were some gnarled and stunted elm trees, the first trees I have seen in Mongolia. They were about thirty feet high, and evidently very old. We then passed over a sandy, barren waste, the beginning of the Galpin Gobi, the very worst part of the whole desert.

(p. 89, 13-May-1887)

Three pages later Younghusband will write:

The Galpin Gobi, where I crossed it to the Hurku Hills, could be seen extending as far as the eye could reach to the N.E. Where Prjevalsky crossed it its width was eighteen miles only, and it was 3570 feet above the sea. The Mongols there told him that it extended to the east and to the west for twenty days’ march. It forms a marked depression in the great Mongolian plateau, and is a distinct dividing-line between the Altai and the In-shan mountain systems, for I will show presently that the Hurku Hills may be regarded as the prolongation of the former mountains.

(pp. 92-3)

It’s clear that the Galpin Gobi is a depression of some length, and that to figure out where Younghusband is heading we need to also locate the large-scale feature of the Altai Mountains, plus the local feature of the Hurku Hills.

One again the 1922 Times Atlas comes in handy. Here we have the Galpin Gobi showing up as the Galbyn-Gobi, and the Hurku Hills as the Khurkha Range. (I might note that KH and H seem to be freely equivalent in transliterations of Mongolian names.)

Some version of the name “Galpin Gobi” also appears on other maps, albeit in slightly different places. Bearing in mind Younghusband’s description of the Galpin Gobi as forming “a marked depression in the great Mongolian plateau,” it’s illuminating to see that although these maps don’t place their versions of the words “Galpin Gobi” in the same place, they do all place them in the same depression visible on a digital elevation model (DEM).

It’s also good to look again at the map which accompanied Przhevalsky’s book, Mongolia, in its English edition. Przhevalsky made his journey through this area in 1873, twelve years before Younghusband, and for the 1876 English translation the publisher (Sampson Low, Marston, Searle & Rivington) had a new map executed. This was probably the most recent map of the area Younghusband had seen.

Przhevalskiy crossed the Galpin Gobi on a North–South line, and there on his map are the “Hurku Mts” and “Bortson Spr” (which Younghusband will shortly mention), as well as a note that here Przhevalsky crossed a Trade route from Peking to Hami, Urumchi & Ili, via Kuku Khoto & Bautu—the very trade route Younghusband is on.

So we can feel confident that this depression between the Lang Shan on the south east and the Hurka Hills to the northwest is the feature known as the Galpin Gobi.

Now, if we back out, we can see both the Galpin Gobi and the Altai Mountains, a major feature that dominates southwestern Mongolia.

As a reference for the Altai Mountains, we can go to this 1967 Soviet Atlas.

If we copy that label onto Google Terrain it would show up like this:

The Hurku Hills are, as Younghusband argues, a prolongation of the Altai mountains to the southeast. But the name Hurku only turns up, in various forms, on the extreme southeast end of this prolongation. The rest of it has other names; Younghusband is the only one who thinks of the whole thing as the Hurku Hills.

Here we can see the “Hurha Uula” (уул [uul] is the Mongolian word for a mountain) on the IMW sheet K-48, and we can see the хребет [khrebet] (mountain range) хурхэ-ула [khurkhe-ula] on the Soviet 1:500,000 scale K-48-3.

On neither map does the labelled range extend very far northwest, whereas on Younghusband’s map the “Hurka Hills” go all the way up to meet the Altai.

So, with the Galpin Gobi, Hurku Hills and Altai Mountains all located relative to one another, let’s go back to Younghusband on May 19th as he reaches the west side of the Galpin Gobi.

we pushed on for the next well, gradually ascending the range, which I now found to be the eastern extremity of the Hurku Hills, the highest part of which was 700 feet above the plain, the track crossing it at 630 feet. We can realize how deceptive the distances are here. Some days ago we first saw this range, and I thought that we should reach it at the end of that march, but we have taken four days to do so. We passed over a plateau at the top of the range for three and a half miles, and then descended very gradually to the plain again, camping at 7:10 p.m. near a well.

(p. 91)

We can visualize this by zooming in on the southernmost point of the Hurka Hills, where they meet the Galpin Gobi depression, and adding contour lines (at 20 metre intervals) to the map.

It is roughly seven contour lines, or 140m (about 450 feet), from the low point of the plain to the pass itself, which does not agree with Younghusband’s estimate of 650 feet, but on the other hand there is, in the pass, a flat area which could creditably be three and a half miles wide. The high points on either side of the pass are up to 250 metres (about 800 feet) higher, not the 70 feet Younghusband implies.

However this pass makes sense because the Bortson well is just around the corner from it.

For two marches we kept gradually ascending towards a watershed, connecting the Hurku with a similar but somewhat lower range running parallel to the road, eight or ten miles to the south. Crossing this connecting ridge, we arrived at the Bortson well in the early hours of the morning of the 22nd. (p. 92)

The Bortson well is quite easy to find on our maps, lying just on the southwest slope of the Hurku Hills: IMW K-48 has it as “Bordzon Bulag (spring)”—“bulak” being a Turki word for a spring), and the Soviet K-48-2 has it as род. Бордзонийн-Булак [rod. Bordzonijn-Bulak], where род. [rod.] is an abbreviation for родник [rodnik], meaning spring or well. The Soviet map also contains the useful note “дебит 2500 л/час” [debit 2500 l/chas] meaning “Flow 2500 litres/hour.”

Bortson well is in a shallow basin, so we can see on the DEM the watershed Younghusband describes himself as crossing: he ascends and then, just before the well, he begins descending.

On the next move (they typically begin travel around noon and end after midnight)…

we continued along the southern base of the Hurku Hills, passing over an almost level plain of an extremely desolate appearance…After this we crossed some low hills running down from the Hurku range, and arrived on the banks of a delightful small stream, about a foot wide and a few inches deep, with some patches of green grass on its margin. Here we halted for three days to buy a couple of new camels.

(p. 93)

It’s unclear where the delightful small stream is. Satellite imagery shows some surface water at a band of rock outcrops about 25 miles beyond Bortson well, which is approximately their daily travel distance.

From here there are not many good landmarks for a few days. In the course of May 28th through June 4th they encounter bad weather, lay over on the 29th, pass over “undulating country” on the 31st, and Younghusband says

to the south there appeared to be good grass-land in the depression between the Hurku Hills and a parallel range, ten or twelve miles to the south. According to a Mongol who visited us, there is some land cultivated by Mongols four miles to the south at Huru-su-tai.

(pp. 94-5)

I have not found any settlement or well that might be Huru-su-tai.

In the next few days we passed along a plain lying between the Hurku Hills and the southern parallel range, for which I could get no name. We saw a peak of the Hurku Hills, which my Mongol called Baroso-khai.

(p. 95)

Of this peak, Younghusband later writes,

the prominent mountain, for which I obtained the name Barosakhai, but which I have not the slightest doubt is identical with the mountain called by the Russian traveller Pevstof, Gourbaun-Seikyn.*

(p. 100)

and in the footnote,

* I found it very hard to get at the proper pronunciation from the Mongols. The n’s are scarcely heard, and it is possible I may not have caught them.

Younghusband seems to be saying here that he might have heard “Gourbaun-Seikyn” as “Barosakhai.” Certainly if one drops the first syllable of Gourbaun, as well as the terminal n’s, this seems plausible: “Bau-seiky” becomes “Barosakhai.”

In any case, Gourbaun-Seikyn is easily found on our maps: it’s a term presently used for the highest portion of what Younghusband is calling the Hurku Hills—the northwest end of the range. Today it is protected as Mongolia’s Gobi Gurvansaikhan National Park. The 1952 IMW K-48 labels this part of the mountains as “Gurban Sayhan,” and the 1972 Soviet K-48-1 has it as ГУРБАН-САЙХАН [Gurban-saikhan].

The high point of the Gurvansaikhan, at just over 2800 metres, is today called Дунд Саикни-Нуру [Dund Saikin-Nuru] and is just northeast of the settlement of Bayandalai.

On June 4th

we reached a Mongol encampment, called Tu-pu-chi. This is the most thickly populated part I have seen in the Gobi, as there were several other yurts scattered over the plain.

(p. 97)

and then

On the following day we crossed a ridge connecting the Hurku Hills with the southern range, and descended a wide valley or plain between those two ranges on the western side of the connecting ridge. Between us and the southern range was a most remarkable range of sandhills, called by my guide Hun-kua-ling. It is about forty miles in length, and is composed of bare sand, without a vestige of vegetation of any sort on it, and I computed it in places to be as much as nine hundred feet in height, rising abruptly out of a gravel plain.

(p. 97)

This forty-mile-long range of sand hills (“Hun-kua-ling“) is one of the most confident identifications we can make along Younghusband’s route. It is recognizably the Khongoryn Els, a notable feature of Gobi Gurvansaikhan National Park. The sandhills (i.e., dunes) are readily seen on satellite images.

This suggests that the encampment Younghusband reached in June 3rd, which he called Tu-pu-chi, is in fact at the site of the present settlement of Bayandalai.

Let’s step back now and compare what we’ve mapped so far to Younghusband’s map.

On the whole they are similar, and there are some interesting features worth mentioning on Younghusband’s map, features that suggest that Younghusband did not himself make the map that appeared in his book.

For one, his mapmaker labels the Kara Narin Ula mountain range curving along the north bank of the Hoang-Ho (Yellow River). Younghusband does not mention this range is his text, but somehow it found its way onto the map. It also shows the Shara Murin river. These features both turn up in Przhevalsky’s expedition account, Mongolia.

Another is that the map has the “Hurka Hills,” while in the text the they are always the Hurku Hills.

Younghusband’s map shows as continuous the secondary range paralleling the Hurku Hills on the south. Yet the DEM shows us that things are not quite so simple. Although Younghusband frequently notices that there are hills to his left, in reality they are not a continuous range until he gets to the basin where Tu-pu-chi/Bayandalai is located.

Continue on to Part 3: from the Hun-kua-ling sandhills to the Ya-hu oasis

Mapping Francis Younghusband in the Gobi Desert, 1887, Part 1: Kwei-hwa-cheng to Galpin Gobi

[Go back to the Introduction]

At the end of Chapter 4 of The Heart of a Continent, it is April, 1887, and Younghusband has travelled northwest from Peking to a town called Kalgan, and then to a further town—from which caravans to the far West depart—called Kwei-hwa-cheng.

I’ll begin by pulling in one of the most useful maps for following his route, Plate 62 from the 1922 edition of the Times Atlas (John Bartholomew and Son, London). We can obtain a scan of this at David Rumsey, and although it was published fully thirty-five years later than Younghusband’s journey, it seems to have continued to reflect British place naming for China, which is often what we need to know.

Zooming in on its northeast corner, to the area between Peking and the province of Inner Mongolia, we can see that in 1922 Kalgan was still shown as a variant name for the city of Chang-kia-kow. Today, in pinyin transcription, this is written Zhangjiakou (张家口 zhāngjiākǒu), and that’s how it shows up on Google Terrain.

Kwei-hwa-cheng had not yet in 1922 been renamed to Hohhot (呼和浩特 hūhéhàotè). But Hohhot has a Wikipedia page, and here we learn that one of its former names was Guihua, which in the 19th century transcription system used by the Times Atlas and Younghusband would have been Kwei-hwa. Cheng is a Mandarin word for “city,” so we can think of Kwei-hua-cheng as Guihua City.

Its name was changed for a time from Guihua to Guisui (this would have been Kwei-sui in Younghusband’s transcription), and then eventually, in 1949, to Hohhot. Hohhot is a variant on the Mongolian name Хөх хот [Höh hot] (which Younghusband writes as Kuku-khoto ) or Blue City.

So we can see that Younghusband’s initial direction from Beijing is west-northwest, which makes sense given that his ultimate destination is Hami. In fact, we can use the Times Atlas map to frame the area Younghusband must cross, from Kwei-kwa-cheng (far lower right) to Hami (mid far left).

What happens next? As he leaves Kwei-hwa-cheng on April 26th, Younghusband records that they ascend into the In-shan mountains:

We left Kwei-hwa-cheng by the north gate of the town, and, after passing for some five miles over a well-cultivated plain, began to ascend the great buttress range on to the Mongolian plateau. This range, called the In-shan, is, as it were, a support to the highlands of Mongolia, and forms the step up on to them.

(p. 81)

Viewed through Google Terrain, Hohhot/Kwei-hwa-cheng sits on a plain with mountains quite close to the northwest.

Google Terrain has no label for these mountains just north of Hohhot, but many maps label them the Daqing Shan, or the In-chan, Inchan or Yin Shan (阴山)—shan being the Chinese world for mountain range. We can easily see it on Tactical Pilotage Chart (TPC) F-8C (1996: Edition 3. See the Perry-Castaneda Library) as Yin Shan. Like Hohhot, the Yin Shan have a Wikipedia page, at “Yin Mountains.”

The next landmark, a stream called the Moli-ho, and a sighting of the Sheitung-ula mountains, does not come until May 7th.

On May 7 we emerged from the undulating hilly country, and, after crossing a small stream called the Moli-ho, came on to an extensive plain bounded on the north, at a distance of five or six miles, by a barren, rugged range of hills, at the foot of which could be seen some Mongol yurts, and a conspicuous white temple; while to the south, at a distance of about twenty miles, were the Sheitung-ula Mountains (called by the Chinese, the Liang-lang-shan, or Eurh-lang-shan), which lie along the north bank of the Yellow river, and were explored in 1873 by Prjevalsky.

(p. 84)

This should be straightforward to find: the stream, the plain, the range of hills five or six miles to the north, the mountains twenty miles south.

Let’s begin with the Sheitung-ula mountains. Przhevalsky shows these on his map as being the range immediately north of and parallel to the Munni-ula, which lie just northwest of the city of Baotu [Baotou]. (Ula is the Mongolian term for a mountain or range.)

The Munni-ula show up quite obviously on Google Terrain, so if we take Przhevalsky’s map literally, we get something like this for the Sheitung-ula.

The later Times Atlas agrees, placing the “Sheiten-ula” northwest of Baotou (“Pao-tow”) and distinct from the Lang-shan.

Now it’s time to pull out the local International Map of the World (IMW) sheet, and the corresponding larger-scale Soviet topographic map. (For more details on what these map series are, see my page on Finding historical place names.) Here, between 108° E and 114° E, we are in IMW zone 49. Between latitudes 40°and 44° north, we are in IMW row K—hence we want the IMW mapsheet K-49. Perry-Castañeda Library at the University of Texas provides us with a 1952 edition from the US Army Map Service, entitled (fittingly) Kwei-Sui.

We can get an even better map from the Soviets for this area north of the Sheitung-ula, on their 1:500,000 scale mapsheet K-49-3.

Looking roughly twenty miles north of what we’ve identified as the Sheitung-ula, we find all the requisite elements. On the Soviet map there is a stream called the Мулэнхэ [Mulen-he]. ( 河 is one of the Chinese words for river, and it is frequently rendered “ho” in European mapping.)

There is a plain to the west of the Mulen-he, with hills on the north side. The Sheitung-ula are distantly to the south, and shown in this Google Earth image.

There is even a temple (although we cannot say if it is conspicuous or white) shown on the IMW sheet, west of what it calls the Mu-leng Ho and just north of the “road” (at least, it was a route in the 1950s). The temple is called the Khatun Süme. The glossary on this IMW sheet informs us that “Süme” is the Mongolian word for temple.

Younghusband’s route between where he entered the In-shan and arrived here at the Moli-ho is purely conjecture, but now we do know where he is after the first ten days.

The next landmark is a stream that Younghusband calls the Ho-lai-liu. This is on the 10th of May.

A small stream—here a few inches deep only, flowing over a wide pebbly bed—runs down from these hills. My guide called it the Ho-lai-liu, and it is probably identical with the stream which Prjevalsky crossed on the southern side of the Sheitung-ula.

(p. 85, 10-May-1887)

The Soviet K-49-3 has a town called Халют [Khalyut]—which is similar to Ho-lai-liu—about 25 miles to the west of the Moli-ho.

But on Google Terrain this town is mysteriously called “Urad Middle Banner,” as well as 乌拉特中旗 (Wūlā tè zhōng qí).

Obviously place names change over 150 years, but let’s just digress a moment and look into this.

Looking nearby we see other towns with “Banner” in their names, such as Dorbod Banner and Qahar Right Middle Banner.

In the Chinese name for Urad Middle Banner, the “Wūlā tè” part seems to be a Chinese version of the Mongolian world “Urad,” and the last two words, 中旗 zhōng qí mean “middle banner.”

This is a hint of the political structure in the Inner Mongolian Autonomous Region. “Banners” (the word 旗 qí also means “flag”) are in effect the counties of Inner Mongolia, and they are in turn divided into sumu, which might be thought of as townships.

We can get an overview of all these names at geonames.org (again, see my page on Finding historical place names). It identifies this place as having no fewer than 20 alternate names, including “Haliut.”

Flowing through this settlement, the Soviet map shows a stream called Халют-гол [Khalyut-gol]. Gol is the the Mongolian word for river. It seems a reasonable conclusion that Younghusband’s stream called Ho-lai-liu was in fact this watercourse.

Another confirming factor is that, just prior to reaching the Ho-lai-liu, Younghusband notes, “we passed close by a spur from the northern range of hills.” This too can be seen in the contour lines on the Soviet map, which shows the road coming into Haliut from the east wrapping around a spur of the hills.

Three days after the Ho-lai-liu, Younghusband notes the beginning of the Galpin Gobi, a section of desert that he seems to be dreading a bit:

On the 13th we passed through some low hills, and then descended a valley in which were some gnarled and stunted elm trees, the first trees I have seen in Mongolia. They were about thirty feet high, and evidently very old. We then passed over a sandy, barren waste, the beginning of the Galpin Gobi, the very worst part of the whole desert.

(p. 89, 13-May-1887)

Go on to Part 2: From the Galpin Gobi to the Hun-kua-ling sandhills.

Mapping Francis Younghusband in the Gobi Desert, 1887: Introduction

In 1887, Francis Younghusband travelled across China, a tale he told in his 1896 book, The Heart of a Continent. Although the book describes Younghusband’s entire journey overland journey from Peking to British India, the part we’re going to look at is specifically the first leg of his trip, the crossing of the Gobi desert from Peking to the town of Hami.

At this point in his life, Younghusband is only 24 years old. He will later—much later—be remembered as the leader of the ill-fated 1903 British military incursion into Tibet, but at this point he is merely a lieutenant, and has taken a leave of absence from his regiment in the Indian Army so that he can travel in China. In Peking he meets a senior British officer—one wonders to what extent these things are actually chance—named Colonel Mark Bell, who tells him of his plan to return to India by travelling overland through regions of western China, areas the British at this time call Chinese Turkestan and Kashgaria. Younghusband asks him if he can accompany him, and Bell offers him one better. Bell would like to take the southern route to Turkestan, going through the city of Xi’an and up through the Gansu corridor, the standard route, if you will, for travel out to Turkestan. Younghusband, he proposes, should take the caravan trade route across the Gobi and meet him in Hami, and then will continue on together from there.

This meets Younghusband’s agenda perfectly, inasmuch as he now has both the blessing of a senior officer for this adventure, and he gets to go on his own. In the end, Bell and Younghusband arrive in Hami on different days, and each completes the journey on to India on his own, an arrangement that, you get the impression, both of them preferred anyway.

Younghusband makes quite a lot out of how he is heading into unknown territory and a blank upon the map, but in reality he wasn’t doing anything new at all—and certainly not “exploring” or “discovering” anything. He hires a camel driver who has been doing the route for the past twenty years, and along the way they find themselves camping with other large caravans going to Hami, or to Guchen, a town northwest of Hami. It’s apparently rather a beaten track across the Gobi. In fact, Bell probably knew all this: his main purpose in sending Younghusband this way was perhaps actually just to document the route. In 1890 we find Colonel Bell giving a paper to the Royal Geographic Society on “The Great Central Asian Trade Route from Peking to Kashgaria,” and there, on his map, is more or less the caravan route Younghusband took to Hami.

Nor is Francis the first European to venture into this area. In 1870, seventeen years before, Nikolai Przhevalsky (Никола́й Пржева́льский) and a party of Cossacks had spent three years knocking about in much the same area, although emphasizing north-south routes rather than east-west. Younghusband had in fact read Przhevalsky’s book, Mongolia and the Tangut Country, which had already been translated into English. So, for all the bold, “Into the unknown” tone he puts on it, Younghusband is really just trying be the first to see this caravan route for his team, as it were.

Nonetheless, The Heart of a Continent is a good read, and he did do a useful thing by making the journey and writing about it. Younghusband is, not surprisingly, a classic Victorian traveller: he is inclined to make sweeping generalizations about the Mongols and the Chinese, invariably thinking of them as having racial characteristics and then comparing them unfavourably with Europeans and the British in particular. But this kind of nonsense is so common in the nineteenth century that we don’t really need to focus on it.

It is doubtful that Younghusband could have imagined that he was leaving, for the 21st century armchair traveller, a wonderful geographical puzzle. We can not only download his book to read for free from archive.org, but we can also open up Google maps, OpenTopoMap or Google Earth and compare it with his map. We can try to figure out exactly where he went, and along the way we learn a great deal about the geography of this area. We can ask What’s in those places today? and If I went there, where would I tell people I was going?

In particular, tracing the Gobi portion his journey is a a challenge, the part where he travels from Kwei-hwa-cheng to Hami, crossing what is today southern Mongolia.

There are eight camels and four men (the camel-man and assistant, plus Younghusband and his Chinese servant) and they are on the journey for seventy days, from April 26th to July 24th. He names many places on the way, but when we go to follow his route on, say, Google maps, we can find almost none of them. Only Hami and the Altai Mountains are there. We cannot find Kwei-hwa-cheng, nor the city of Kalgan, which is his first stop after leaving Beijing. There is no river called the Moli-ho, no desert called the Galpin Gobi.

There are multiple reasons for this. For one, there was no standardized transcription method for converting Mandarin into Roman characters in 1887. It looks like Younghusband uses the Wade method, which was coming into use among Europeans at the time, but he may also simply be copying names off the European maps he has, and making the spelling up when he learns new names. In any case it looks rather different from the pinyin transcription method we use today. He writes Peking; we write Beijing.

Second, many place names have changed. Kalgan isn’t Kalgan anymore: it’s Zhangjiakou. Kwei-hwa-cheng is called Hohhot. A reference work on the changing names of places in China over the past hundred and fifty years would be terrifically useful, but as far as I know it does not yet exist.

Finally, the 21st century online mapping services, point-oriented and focused on the wired world as they are, don’t have a lot of labelling on the linear and areal features (rivers, deserts and mountain ranges) of what is today the Chinese province of Nei Mongol (Inner Mongolia), or of southern Mongolia proper.

But, by working back and forth between old maps and new, we can figure out a lot of the details of this journey.

Go on to Part 1: From Kwei-hwa-cheng to the Galpin Gobi.

Shaded Relief using Skymodels, courtesy of Raster Chunk Processing

A couple of weeks ago I watched some excellent presentations from the How To Do Map Stuff day organized by Daniel Huffman. One that I particularly enjoyed was Jake Adams’s talk on building shaded relief out of hillshades. Toward the end of his talk he brought in something called a skymodel.

In this post, I’ll explain what Skymodels are, and how to get Jake’s Raster Chunk Processing software running in a linux environment so you can use the Skymodel feature to make your own versions of this unique kind of shaded relief.

Skymodels were introduced in a paper by Pat Kennelly and James Stewart in 2014. The basic idea behind the skymodel is that, in the real world, we see terrain illuminated by light coming from all parts of the sky in various amounts, not just from the sun. The usual hillshading algorithm, on the other hand, calculates what’s illuminated and what’s in shadow based entirely on light coming from a single point.

An overcast sky is one example of a skymodel: in the overcast sky, light comes mostly from above, but not from any particular direction.  In James Stewart’s SkyLum software, this is represented by the redder, “hotter” dots in the dome of the model, while we have yellow and then cooler blue dots down toward the horizon representing less light coming in from those directions.

skymodel_overcast

Contrast that with this model for what SkyLum calls a Type 6 sky, “partly cloudy, no gradation towards zenith, slight brightening towards the sun.”

Type 6 partly cloudy, no gradation towards zenith, slight brightening towards the sun

Or this, the Type 13, “CIE standard clear sky, polluted atmosphere.”

type 13 CIE cstandard lear sky, polluted atmosphere

Each of these will produce a different kind of shaded relief.

Baltoro_assortment
The Baltoro glacier, Pakistan. Left: overcast. Middle: type 6, “partly cloudy, no gradation towards zenith, slight brightening towards the sun.” Right: type 13, “CIE standard clear sky, polluted atmosphere.”

In Blender you can position multiple light sources, but SkyLum writes a CSV file (which I will call the illumination file) that defines 250 different light sources and assigns a relative weight to each. This is new level of complexity in lighting.

180,45,0.000962426
175,37,0.000929834
193,47,0.00118523
187,38,0.000949383
167,47,0.00143157
181,54,0.00168069
169,41,0.00141631
...

Each line in the illumination file above gives the azimuth, elevation, and weight for one illumination source. The weights for all 250 points will add up to 1.

So how does one use this to generate shaded relief?

Well, Jake Adams (thank you, Jake!) has written a clever piece of code called Raster Chunk Processing (RCP, hereafter), which he presents in a three-part blog post. RCP divides up large DEMs into smaller tiles (“chunks”), each of which is processed separately. All of the results are then merged back together for a final result. The point of RCP is that it allows you to work with DEMs that ordinarily would max out your RAM and cause processing to grind to a halt.

This is similar to the way I have divided large DEMS into tiles for processing by Blender, but Jake’s RCP code allows you to use this “divide-and-conquer” strategy to do a whole host of things. One of them is to build a skymodel hillshade, given a DEM and an illumination file from SkyLum.

The RCP code is written in python, which is platform independent, so although Jake gives us instructions for installing it under Windows, we can get it running under linux with just a few changes.  In this case I did this on a system running Ubuntu 18 Bionic, and since I was using this machine for mapping I already had QGIS and GDAL installed.

To begin, head over to Jake’s Git repository, and download the RCP software using the Clone or Download button. Once unzipped, this will produce a directory called rcp-master. Within it you will see, among other things, the main program (raster_chunk_processing.py), a subdirectory called SkyLum (which contains the SkyLum program) and a couple of other python files that will be important to us, like settings.py and methods.py.

RCP is written to be run under python 3, so from a Ubuntu point of view these are the packages you will need to install:

  • python3-numba
  • python3-astropy
  • python3-gdal
  • python3-skimage
  • python3-numpy

(Note that python3-scimage replaces the module Jake calls scikit-image.)

Another thing that RCP needs is a working copy of mdenoise, the software that implements Sun’s algorithm for denoising topographic data. Or rather, RCP needs to at least think it has a copy. So you have a choice: if you want to be able use RCP to denoise DEMs, you should compile yourself a copy of the mdenoise binary; there are instructions here, and it’s not too painful. If not, just use sudo to place an empty file called mdenoise in /bin.

Then use a text editor on the file settings.py to alter its single line about where the mdenoise executable is.

MDENOISE_PATH = '/bin/mdenoise'

The last piece you have to put in place is a way to run SkyLum. SkyLum only comes as a Windows binary, SkyLum.exe, so to run this you need to have wine installed. The good news is that SkyLum runs quite well under wine.

Right-click SkyLum.exe, and choose Open With… >Other Application. In the list of application choose, “winebrowser.”

winebrowser

SkyLum should open right up and show you a piece of terrain with a sky dome over it.

fresh skylum

The complete instructions for SkyLum are in the README file included with it, but I will give a summary here of what I find useful:

  • By default when you open SkyLum the sun (sun position is shown at the bottom) is at 45° elevation and azimuth 180° (due South). 0° is north, and azimuths increase clockwise, as is standard
  • Hit ? for a help screen
  • Move the sun with the arrow keys.
  • Rt-click and choose an illumination model. See Kennely and Stewart’s paper for more on these.
  • Hit p to have SkyLum.exe calculate points after you have positioned the sun and chosen a skymodel
  • Hit o to have SkyLum write a sky model file. It’s conventional to give it a .csv extension.
  • Use a text editor to delete the header lines. All you want left are the comma-separated lines with the azimuth, elevation and weight, as shown above.

Now, how to run RCP?

Let’s assume you have a DEM  called myDEM.tif, and an illumination file you made with SkyLum called illum.csv. You’ve already deleted the header lines from illum.csv. You want to divide your DEM into 1000x1000px chunks, with an overlap of 200 px. We’ll also assume you have 4 processors and you want to use 3 of them for this operation.

Drop both myDEM.tif  and illum.csv in the rcp_master directory. Open a terminal there.

The general form of the RCP command line is:

python3 raster_chunk_processing.py -m [method] {general options} {method-specific options} input_file output_file

Notice that the first element in the command line is python3, not just python.

For my skymodel in this case the command line will be…

 python3 raster_chunk_processing.py -m skymodel -s 1000 -o 200 -p 3 -l illum.csv --verbose myDEM.tif myDEM_skymodel.tif

What you’ll see in the terminal is a bunch of information about the job to be done, and then you’ll see RCP submitting the sub-jobs (the chunks) to be skymodelled. You can walk away, or watch, fascinated, as the chucks get worked on…

Preparing output file myDEM_skymodel.tif...
Output dimensions: 4046 rows by 4515 columns.
Output data type: <class 'numpy.float32'>
Output size: 69.7 MiB
Output NoData Value: -32767.0

Processing chunks...
Tile 0-0: 1 of 25 (4.000%) started at 0:00:00.701178 Indices: [0:1200, 0:1200] PID: 8777
Tile 0-1: 2 of 25 (8.000%) started at 0:00:00.701253 Indices: [0:1200, 800:2200] PID: 8778
Tile 0-2: 3 of 25 (12.000%) started at 0:00:00.701284 Indices: [0:1200, 1800:3200] PID: 8779

All of the switches and parameters are explained quite well in Jake’s post. My additional notes are:

  • the input file is generally a geotiff, but it can also be a TIF/TFW pair. It has to have a NoData value defined or you will get an error No NoData value set in input DEM.
  • RCP will exit with an error if the output file already exists
  • By default RCP applies a vertical exaggeration of 5X to the DEM, because this was what Kennely and Stewart did in their paper. However, you can change this if you would prefer a different vertical exaggeration. Open methods.py in your text editor and go to line 272. This line originally says  in_array *= 5. You can change that 5 to whatever number you would prefer. (No recompile necessary.)
  • the overlap (-o) parameter is based on how far you think shadows may stretch. The shadowing algorithm checks outward for 600 pixels to see if a given point is shadowed by anything. For this reason, there is no point in making overlap larger then 600.
  • the chunk size parameter (-s) is based on how much RAM each process requires while running. You can experiment with this and watch on the system monitor to see how close you are to spilling over into swap.
  • When shadows are being calculated in the skymodel,

The output file can be dragged into QGIS, where I often find I want to increase brightness.

adjusdting_brightness
Left: hillshade image fresh out of RCP. Right: with brightness +100

Another idea that seems to produce some nice results is to combine two or more skymodels with different transparencies and styling. You might also want to check out a gallery of the results of applying all of the different skymodels in SkyLum to the same piece of terrain.

Now that you have RCP running, of course you’ll need to try all of the different skymodels on your favourite DEM to see which you like best. But it’s also worth checking out the other kinds of processing RCP can do on DEMs. It is a very fast conventional hillshader (method hillshade). It runs a nice, quick gaussian blur (method blur_gauss), much faster than the SAGA Gaussian filter module in QGIS. And I haven’t even tried the Clahe and TPI processing yet!

 

 

 

The Hollow Plain of Ka’ra

I learned about the existence of  the hollow plain of Ka’ra, in Iraq, when I was reading Gertrude Bell’s letters.

On the 10th of February, 1911, Gertrude, who is forty-two years old, sets out across the Syrian desert from Damascus to go to Hit, some 600 km east, on the Euphrates River. Both of these cities are, at this time, in the Ottoman Empire, so there are no international borders to be crossed.

She begins on a horse.

I rode my mare all day, for I can come and go more easily upon her, but when we get into the heart of the desert I shall ride a camel. It’s less tiring. (Feb 10)

Not alone, Gertrude (who is fluent in Arabic) is in part of a party of fifteen, some of whom are her employees. She describes them as…

myself, the Sheikh, Fattuh, ‘Ali and my four camel men, and the other seven merchants who are going across to the Euphrates to buy sheep.

For much of this journey they are outside of the zone of Ottoman control.

In half an hour we passed the little Turkish guard house which is the last outpost of civilization and plunged into the wilderness.

Their exact route is not easy to trace from her letters—she does not give many landmarks—but on February 16th she reports that

We came to the end of the inhospitable Hamad today and the desert is once more diversified by a slight rise and fall of the ground. It is still entirely waterless, so waterless that in the Spring when the grass grows thick the Arabs cannot camp here.

She uses the term Hamad to denote the core of the Syrian desert, the highest, flattest part—although other writers call the entire the Syrian Desert the Hamad. On the next day (17th) she writes that they have deviated from their route, which, up to this time, had been almost due east.

So it happened that we had to cut down rather to the south today instead of going to the well of Ka’ra which we could not have reached this evening… the whole day’s march was over ground as flat as a board, flatter even than the Hamad…We had a ten hours march to reach the water by which we are camped.

The 18th…

we got off half an hour before dawn and after about an hour’s riding dropped down off the smooth plain into an endless succession of hills and deep valleys – when I say deep they are about 200 ft deep and they all run north into the hollow plain of Ka’ra.

This is the last we hear about the hollow plain of Ka’ra, which apparently has a series of north-flowing canyons running into it from the south. On the 20th they arrive at the ruins of Muḩaywir in the Wādī Ḩawrān.

We rode today for 6 and a half hours before we got to rain pools in the Wady Hauran, and an hour more to Muhaiwir and a couple of good wells in the valley bed.

The Wādī Ḩawrān and Muḩaywir are not difficult to locate. They show up on this 1959 Times Atlas map of the Middle East, along with the sites she now visits on her way to Hit: Amij, Khubbaz and Kubeisa.

Times_atlas_markup

But Ka’ra (or “Kara” as it is spelled in the printed edition of Bell’s letters, rather than the online archive of her diaries and letters) is not there.

Now, if you’re quicker than me, you probably already picked up that on this map, just to the west of Wādī Ḩawrān, there is a “Jumat Qa’ara”—and reasoned that this might be what Gertrude referred to as the hollow plain of Ka’ra. But I missed that, and began a pointless search of Google Maps, OpenstreetMap, geonames.org and Wikipedia for something called the Ka’ra.  (There is a Wikipedia entry for “Kara Depression,” but this is a Kara Depression in northern Russia.)

I did, however, noticed on the shaded relief of OpenTopoMap that 40 km west of Muḩaywir there was a 50-km-wide depression with a series of canyons flowing into it from the south. Was this the “the hollow plain of Ka’ra?”

opetopomap_annotated

But this feature goes unnamed on online mapping sites.

This shows the weakness of much of online mapping: it is point-based. Area features, which are readily labelled on what we can call “static maps” (maps designed to be printed, or to be a single image you can’t zoom in on) do not make it into the database that underlies slippy maps. Neither do linear features, like rivers. I do not know why OSM, Google et al. try to make everything into points, but points dominate online mapping.

(As an amusing exercise, try typing “Yangtze River” in the search box on Google Maps. You don’t get a very satisfying result.)

 

However, by luck I found an article by another famous British archaeologist,  Sir Aurel Stein, written some twenty-nine years later. He was writing about his search for Roman forts along the line from Hit to Palmyra. A lot had changed. World War I had happened; the British had created the mandate state of Iraq; they had built the pipeline to carry the oil from Kirkuk to the Mediterranean, and put pumping stations along it; aircraft were in common use. Stein wrote…

after gaining the pipe-line station H2 for a base, we resumed the survey of the ancient trade route which had led from Hit to Palmyra. I was able to recognize its line clearly both from the air and on the ground also over long stretches right up to where Pere Poidebard had before determined its continuation beyond the Syro-‘Iraq frontier. The line proved to have led with characteristic Roman straightness right across the wide sandy depression of Qa’ara, and not as had been supposed before past the ruins of Qasr Helqum.

Ah, “the wide sandy depression of Qa’ara!” And on his map, there it is, just north of the H2 pumping station, and northeast of Mlosi, labelled as “Al Qa’ara”.

Stein map 1940

Ironically, the online mapping sites do not even show the H2 pumping station and airfield, although it used to be a standard feature on static maps, like this National Geographic 1960s map of the Middle East.

NG Middle East 1970 detail

Mlosi, which Stein also called the “well of Mlosi,” is shown on the National Geographic map as Bi’r al Mulusi, and is probably the same as the Ābār al Malūsī (ابار الملوسي) located by geonames.org at N 33°29′48″ E 40°06′14.  (Ābār being the plural of Bi’r, a well.) Qasr Helqum would be Qaşr al Ḩalqūm which geonotes.org places visibly on the north rim of the depression.

Google Hybrid with annotation
Google Hybrid of the hollow plain of Ka’ra/Al-Qa’ara, with labels added manually

Bell doesn’t indicate whether she had heard of the Ka’ra before, but Stein refers to “the wide sandy depression of Qa’ara” as if it is well-known. How did he learn about it? What maps was he using? It would also be nice to know how it is spelled in Arabic, so we could know how it should be transliterated to the Latin alphabet.

 

GE view of Qa'rah
Al Qa’ara as seen on Google Earth, looking southeast, with the “deep valleys” running “north into the hollow plain.”

Well, it turns out, if I look at more static maps, the hollow plain is consistently labelled.

The 1986 Soviet 1:200,000 scale topographic map I-37-23, has “ВПАДИНА КААРА” ВПАДИНА is a depression.

Kaara on Soviet 200K I-37-23

A 1944 by British Naval Intelligence, from the Perry-Castaneda Library: shows it as “JUMAT QAARA.” (And this is what I see, looking back at the Times Atlas, above.)

1944 Naval Intelligence western Iraq detail

And the 1942 map from the US Army Map Service (NJ-43-11 “Rutba”), calls it JUMAT AL QAARA

1942 AMS quarter inch I-37 Q Rutba detail

There are also a number of recent geological papers about this feature. Mustafa and Tobia have one called Modes of Gold Occurrences in Ga’ara Depression, Western Iraq, in the Iraqi Bulletin of Mining, 2010. Their map leaves no doubt that the Ga’ara Depression is the same as Bell’s Ka’ra and Stein’s Al Qa’ara.

Mustafa and Tobias map

The paper’s abstract is in Arabic, so we can see how they render “Ga’ara Depression” in Arabic.

Tobia article titles

“In Ga’ara Depression” is in_ga'ara_depression_ar, which uses the unusual letter gaf-with-line (گ), a variant on kāf (كـ ) which is regularly used in Persian, a language that has a /g/ sound. منخفض Munkhafidun is a depression. 

It’s a confusing variety of transliterations: Ka’ra, Qa’ara, Ga’ara. What helps make sense of it is that (as I learn at https://en.wikipedia.org/wiki/Varieties_of_Arabic), the letter  ق, pronounced /q/ in classical Arabic, has become a /g/ in both the Iraqi and Nejdi dialects. Typically they still spell these words with a  ق  (as in Qa’ara), but sometimes they are using the gaf-with-line (as in Ga’ara).

Poking through an Arabic-English dictionary I see that the Q-‘-R triliteral root in Arabic means to be deep, or hollowed out. So, ironically, Qa’ara may simply mean the deep, hollowed out place. This may be why Gertrude Bell called it “the hollow plain of Ka’ra.”

So, now I know where this hollow, sandy plain is, but I am left with one mystery that I can’t solve. On the maps where it is labelled Jumat Al Qaara, or Jumat Qa’ara, what does Jumat mean? Jum’ah (جمعة) is the word for Friday, but it seems unlikely that this is the Friday of Hollows. The J-M-‘ root means to gather or collect, so conceivably this is the Collection of Hollows? I could not find other Jumats to compare this to. Any ideas from Arabic speakers would be welcome.

 

 

 

How do we understand the size of Syria?

Syrian_comparison_inset_2004_CIA

This inset appears on a CIA map of Syria from 2004. We can assume it’s meant to give the map reader a sense of the size of Syria by comparing it to a region that he or she is familiar with.

I’m fascinated, first, by the assumption that the decision-maker reading the map is located in the mid-Atlantic states, (Washington, presumably). This kind of regionality runs throughout American politics, a geography of where important people live, and where they don’t, that one carries in the memory and consults without even knowing it. 

This is an attempt to make the map *personal* but I almost think it should be captioned, “This might be helpful to you if you happen to live in the northeast.”

The second thing I’m fascinated by is, assuming we have to stick to the northeast USA, would it have been a smarter decision  to have aligned Damascus with Washington, DC? These are the two national capitals. Such a juxtaposition would, in the context of the Syrian Civil War, allow the President to imagine New York no longer doing his bidding, and Providence functioning like an independent state.

CIA inset Washington and Damascus aligned

Perhaps this juxtaposition puts too much of Syria out to sea, but it does put New York City more or less where Raqqa, the ISIS capital, was.

Of course one must always be careful when constructing these comparison maps. In GIS software a polygon (Syria) whose coordinates are in degrees, dragged to another latitude, will be the wrong size. The safer method, which I have used here, is to make separate maps at the same scale of both Syria and the northeast US, and then juxtapose them in a photo editing program (the GIMP, in my case).  Syria is about 780 km from end to end on its long axis, about the distance from Boston to Richmond, Virginia.

This brings up the question of what it means to understand distance. In the original map, what does the distance from, say, Philadelphia to the eastern tip of Tennessee, mean to people living in Washington? I suspect they rarely go very far to the southwest from the city, and when they do they experience slow, twisting roads that have difficulty passing through the Appalachian mountains. So if the Washington-dweller says “It would take me six hours to drive to the tip of Tennessee!” is there anything meaningful at all there for his understanding of Syria?

I kind of prefer this juxtaposition, both for the similarity of desert landscape, and the sense of distance.

CIA inset LA and Damascus aligned

Los Angeles stands in for Damascus here, and Las Vegas finds itself somewhere up on the Euphrates. (“Las Vegas on the Euphrates” is not yet, but may someday be, the tourism slogan of Deir Ez-Zur or Raqqa.) If you are familiar with the distances and deserts of the American southwest, it is remarkable how much smaller Syria looks when shown like this.

Of course, as Appalachian Trail hikers know, there happens to be a town in Virginia called Damascus. It’s actually right there, just across the border from that eastern tip of Tennessee. So perhaps the best juxtaposition of all aligns Damascus, Virginia, with Damascus, Syria.

CIA inset Damascus and Damascus aligned

 

 

Digital Atlas of the Roman Empire

Fans of the Digital Atlas of the Roman Empire basemap (or DARE basemap) may have noticed that it disappeared from Peripleo a few months ago!

Peripleo is the superb mapping site where you can look up the locations of places in the ancient world. It is is absolutely indispensable in those moments when you just can’t remember which modern town occupies the site of ancient Mesembria. Which happens to me a lot. Also Sirmium.

At present when you look at the available layers in Peripleo, The satellite layer (“Aerial”), Openstreetmap (“Modern Places”)  and the empty basemap are there, but no DARE (“Ancient Places”).

peripleo map layers dialogue

Even more worrisome, the old URL for visiting the DARE map where it was hosted at the University of Lund, Sweden, http://dare.ht.lu.se/,  was not responding.

However, DARE is now back! The map has been moved to a new location at the the Centre for Digital Humanities, University of Gothenburg, https://dh.gu.se/dare/.

new DARE

Many thanks to its creator and maintainer, Johan Åhlfeldt.

Better yet, he has also given out the URL for the tile server itself, so if you run QGIS you can now add DARE as a basemap layer in the QuickTileServices plugin.

Here’s how:

Go Web>QuickMapServices>Settings

settings

Go to the Add/Edit/Remove tab.

adEditRemove

Click the ‘+’ button next to My groups, and create a DARE group.

addGroup

Click OK and then click the ‘+’ button next to My Services. First add the name of the service and choose TMS for Type

addService1

then go to the TMS tab and fill in those parameters:

addService2

Click OK and then Save, and your service is set up.

It should now appear on the Web>QuickMapServices menu.

dare example

Also, since tile-based services operate at zoom levels that correspond to a very strange  set of scales (like 1:1,155,583), remember that you can always snap to the nearest tile scale by going Web>QuickMapServices>Set proper scale.

Happy ancient world mapping!

 

Shaded relief with BlenderGIS (2019), part 3

[Back to Part 2]

Why do this?

The shaded relief images (also often called a hillshade) that GIS software produces are pretty good. Here’s one made with QGIS.

QGIS 2-up
The hillshade by itself (left), and blended with hypsometric tinting (right)

Hillshading algorithms typically take three parameters: the elevation of the sun, the azimuth (direction) of the sun, and the vertical exaggeration of the landscape. (60°, 337° and 1X, in this case.) They do some geometrical calculations to figure out the intensity of incident light on all the pieces of the landscape, and then produce a greyscale image. (They do not, typically, however, calculate actual thrown shadows.)

You can tweak the brightness and contrast in your GIS software, or stretch the histogram to your liking. This can do a lot to lighten up the darkest shadows, or to turn the hillshade into a ghostly wash that merely suggests relief without dominating everything else on the map.

Much of the time what we can get out of GIS software meets our needs for a hillshade, which, after all, is not the final map but a merely a layer of the map. (Although occasionally it is the pièce de résistance…)

But perhaps you don’t like the glossy, shiny quality of that hillshade above. You think the mountains look like they were extruded in plastic. They remind you a little too much of Google maps Terrain layer. Maybe you’d like to see actual shadows thrown by precipitous cliffs. Maybe you’d like something that looks more like it was chisled from stone, like this…

Blender 2-up

Or perhaps you are interested in…

Blender 2-up 2 suns
A second sun, shinning straight down to eliminate the darkest shadows

Blender 2-up warm and cool light
A warm (yellow) sun in the northwest, cool (blue) shadows

Blender 2-up denoised
Denoising performed on the image after rendering

This might be why you are investigating Blender.

The big settings that make a difference (besides the conventional settings of azimuth, elevation and vertical exaggeration) are…

  • material
  • multiple lights and their colours
  • amount of light bounce
  • denoising the render

Material

In animation modelling, Material is what reflects, absorbs and scatters light. Blender spends much of its time tracing light rays and deciding how the surfaces they encounter affect them.

With your plane selected, go to the Material tab icon Material tab and hit New. The default material that comes up has these Surface properties. (And this is what Blender used for your basic render.)

Principled BSDF initial properties

Principled BSDF is a sort of super-versatile material that allows you to have all of these properties (subsurface scattering, metallic look, sheen, transmission of light) that in earlier versions of Blender were assigned to specific surface types, like “Diffuse BSDF,” “Glossy BSDF” or “Subsurface scattering.”

(BSDF stands for “bidirectional scattering distribution function.”)

These various surfaces are actually shaders, which are pieces of software that render the appearance of things (and may actually run on your GPU, not your CPU). If you click on “Principled BSDF” next to the word “Surface” a list of all of the possible shaders comes up.

shader list

You can learn a lot more about shaders in the Blender manual, but Blender essentially wants to give you the tools to be able to simulate any material, from water to hair, and some of the effects you can get applying this to shaded relief are pretty weird.

8 kinds of material
The same piece of terrain rendered with different shaders. Top, left to right: Diffuse BSDF with a wave texture, Glass BSDF, Hair BSDF, Principled BSDF. Bottom, left to right: Toon BSDF, Translucent BSDF, Translucent BSDF with Principled volume emission, Velvet BSDF.

The main shader you probably want to play with is the Mix Shader, which allows you to mix the effects of two different shaders. The Mix Shader’s  factor (from 0 to 1) determines how much the results are influenced by the second shader.

Mix Diffuse Glossy
On left, the original render; on right, a Mix shader (Fac=0.2) of Diffuse BSDF (defaults) and Glossy BSDF (IOR=2). This adds just a bit of glossiness to the surface.

Mix Diffuse Toon
On left, the original render; on right, a Mix shader (Fac=0.3) of Diffuse BSDF (defaults) and Toon BSDF (defaults). This brings in bright highlights that tend to wash out flat surfaces.

The other aspect of material that is worth experimenting with is value. Blender’s default material, the Principled BSDF, has a default colour of near-white, and its value is 0.906 (on a scale of 0 to 1).

principled BSDF default base colour

By darkening this you create a more light-absorbing material.

Principled BSDF base colour 0.5 lamp 45 337 str 3 v2
On left, the original render; on right, Principled BSDF (base color value turned down to 0.5).

You might think that the effect of a darker material is just to shift the distribution of pixel values down in the render, and that you could get the same effect by turning down the brightness of the original. But if you look at the histogram of each image you see the pixel values are distributed differently, and even when both are displayed with “histogram stretch,” they are distinct from each other.

base color 0.906 versus 0.5 both histogram stretched
Left: the value of the base color of material (Principled BSDF) is 0.906 (the default). Right: the value of the base color is 0.5. Both are displayed with histogram stretch.

And of course if it works for your map you can give the material real colour. (Don’t forget to save the render as RGB rather than BW). This, however, is very similar to colorizing your shaded relief in GIS software.

sandstone yellow material

Multiple lights and their colours

To add another light to your scene, go Add>Light>Sun. You can also experiment with adding other types of lights: point lights (which shine in all directions from a specific place), spot lights (which send out a specific cone of light) and area lights.

A second light can bring out features in a very nice way.

second sun from the east
On left: vertical exaggeration 2x, one sun in the NNW, elevation 45°, angle= 10°, strength = 3. On right: the same scene plus a second sun in the east, elevation 45°, angle = 1°, strength 0.5.

By giving colour to lights, you can create differential lighting and colour.

Diffuse 2x BSDF default 45 337 str 3 color orange LAMP2 str 0.5 az east color yellow
Same scene as above, but now the sun in the NNW is orange, and the sun in the east is yellow.

There is one more light in your scene that often goes unnoticed, and this is what Bender called the world background colour. You can think of this as a very far away surface that nonetheless does contribute a bit of light to your scene—from all directions. You can see the world colour in action if you render your scene with the sun strength turned down to 0.

world background only
No lights in the scene: mysteriously there’s still something there. This is the effect of the world background colour.

If there are places in your scene that sunlight does not reach, the world background still contributes to their illumination—and colour.

By default the word background colour is 25% grey (value = 0.25), but you can change this to a dark blue if you would like dark blue light to collect in your shadows.

world background blue
World background colour set to blue (Hex 414465), strength 1. Secondary pale yellow (Hex FFE489) light in east, strength 0.5

Amount of light bounce

Part of the charm of Blender is that it calculates how much light reflects off surfaces and then hits other surfaces, which is why even shadowed areas have some light. You can control, however, the number of bounces a light ray has before it expires. This is on the Render tab icon Render tab, in the Light Paths section.

light paths default

By default, the light paths settings are as above. With the material I am using, the Max Bounces for Diffuse materials is the important part, and by default it is 4.

The presets exist icon icon to the right of “Light Paths” indicates that there are presets available. Clicking here reveals three key presets:

  • Direct Light: light gets few bounces, and none off diffuse material
  • Limited Global Illumination: light gets one bounce off diffuse material
  • Full Global Illumination: light gets 128 bounces off diffuse material

Changing among these does not make a huge difference, but in scenes with deep shadows it is visible.

light paths compared
Clockwise from top left, the presets are: Direct Light, Limited Global Illumination, Full Global Illumination, and the default settings. (With vertical exaggeration at 2x)

Denoising the render

Blender offers the post-processing feature of denoising the render. I liken this to a blanket of snow on your landscape: it erases tiny details.

denoise comparison
Left: 2x vertical exaggeration, sun in NNW, elevation 45° strength 3. Right: the same, plus denoising (Strength = 1, Feature Strength = 1)

To activate denoising, go to the View Layer tab icon View Layer tab, scroll to the very last section, Denoising, and check the Denoising box.

denoising panel

I do not find that denoising does much if you keep the default settings. I tend to turn both Strength and Feature Strength up to 1.0.

In conclusion

This is only been the tip of the iceberg. Some things I have not talked about are

  • Applying a subdivision surface modifier to your mesh so that Blender is interpolating and smoothing it on the fly.
  • BlenderGIS’s ability to read your DEM As DEM Texture, which creates a plane with subdivision and displace modifiers instead of a plane whose every vertex corresponds to a DEM cell.
  • How to focus the orthographic camera down on one small part of your DEM where you can do quick test renders while you work out lighting, material, etc.
  • The node editor for complex materials
  • Using a perspective camera to shoot a scene that is not straight down
  • Cutting DEMs into tiles for Blender to work with, when the whole DEM is simply too much for the RAM on your computer.

Have fun exploring Blender’s many features!