OpenStreetMap
The Sentinel-2 satellite finally captured a cloud free coverage of the 2018 Laos Dam Collapse site. Over a distance of more than 50km, everything near the river has been washed away, trees being stripped bare from the river banks.
Comparing it to the river pre-disaster shows how much energy was in the water: https://gfycat.com/LeadingAbsoluteConure
The map below shows what happened, one of the secondary dams overflowed, causing the reservoir to drain into another river.
On 24 June 2017, a big landslide occured in China’s Sichuan province, burying dozens of villagers alive. Although pictures from the ground clearly showed that most victims didn’t have a chance for survival, satellite imagery shows the scale in one glance:
(source: ESA Copernicus Sentinel 2. 19 February 2017 and 7 September 2017.)
I’m tempted to replace all those named as clinic by the tag amenity=clinic, but maybe someone who has lived in Korea can confirm if that’s appropriate?
Use this to find them: http://overpass-turbo.eu/s/rRX
To name a few things in the above area:
residential roads tagged as motorways, primary or secondary
the same road went from motorway to service to residential to primary
island roads (not connected to rest of network)
roads ending just before the crossing
roads split in arbitrary segments all over the place
ways with a node for every half a metre length
And how about this?
It’s not exactly a secret that the official Chinese government statistics are often made up or obfuscated. The official stats for road network length say 4,696,300 km of roads. According to the CIA world factbook, China has 4,046,300 km of paved roads. In 2016, on OSM 1,635,931 km of roads was mapped in China. Update: in June 2017 we’re already at 2,022,047 km!
Now compare the OSM data of a typical countryside area to the satellite imagery.
Pretty much all unclassified roads are still missing from OSM, and this is the case for most of rural China. Even for cities, there are only a handful of cities that have their residential roads mapped well. So it leaves me wondering, is the 4 million km of roads in total a realistic statistic?
USGS has published tree cover data based on 2010 Landsat captures. I wonder if this data would be suitable for importing. Especially outside of Europe, forest cover is largely incomplete now, and 2010 is fairly recent for this kind of data.
https://landcover.usgs.gov/glc/TreeCoverDescriptionAndDownloads.php
In the licence requirement it says: University of Maryland, Department of Geographical Sciences and USGS; use is free to all if acknowledgement is made. So it is not obvious if using this data is allowed.
The data is provided asgreyscale geoTIFFs, i have uploaded one tile as a preview here:
If you map in the West you may come to think that the major stuff in OSM is done, but in developing countries, you may discover major unmapped features.
I’ve been mapping lots of countryside in Gansu, China, and the number of temples is quite high.
In the predominantly muslim areas, mosques are usually very easy to recognize (although I hope I didn’t miss too many because of tunnel-vision), due to the usually square main building with a central dome, surrounded my 2 or 4 minarets.
Buddhist and Taoist temples however, are impossible to distinguish for me, as someone with only basic knowledge of Chinese architecture and these two religions. On the ground I would probably be able to, but with the number of local mappers in rural Gansu and my travel budget not being impressively high, all there is left is studying Bing imagery.
Some examples:
Without looking, can you tell which one is Buddhist? Of those listed, one was documented, so I could confirm (or rather, correct) that is is Buddhist: osm.org/way/454051191
Besides purely looking at the architecture, the location also gives things away of course. In a Hui autonomous county, you expect to find more mosques, in a Tibetan Autonomous Prefecture, you expect more Buddhist temples. Some temples are located on hilltops, others within a residential area and others are surrounded by farmland. I don’t know what significance this has, but surely, there must be some.
If you know the name of the temple, this can apparently also give you a hint. https://en.wikipedia.org/wiki/Chinese_temple
Chinese religion experts, please let yourself be heard in the comments or via a message.
Population numbers turn out to be pretty important for rendering places at the correct zoom level. Since ‘town’ or ‘city’ is the highest possible qualification for any large urban centre (whether a sleepy 100 000 population suburb or a 10 million population metropolis) there may be many of these places very near each other. On lower zoom level, the renderer has to make a choice on which cities to show. Without any population numbers, no decision can be made, thus no names are rendered.
The default Carto layer does take population into account, and it can be seen that it is a major factor in deciding which place is shown at lower zoom levels.
In green are cities I’ve recently added population number to (number is brackets is the urban population). These are all rendered as long as the labels fit nicely without overlapping. It is not strange that the desert town of Hami is labeled at this zoom level. It should be, because it is a major stop along this transport corridor.
在中国駕駛人校让学生来练习在闭路，平素也有练道，可能是相当长。
我的问题是，这就是’highway=raceway’？
我也用’amenity=driving school’，可是，最多呈现没表示。此外，可能办公室是在别的地方。例如如果学校有体育场在别的地方，这个体育场不是’amenity=school’。所以，可能我应该只用’highway=raceway’ tag.
In China, driving schools operate closed circuits where students practice. These may include tracks that can stretch for a kilometer or so. Currently I usually tag the grounds as ‘amenity=driving_school’ and the track with ‘highway=raceway’. However, this may not be correct, as the driving school may have its main office elsewhere. You wouldn’t tag a sports pitch as ‘amenity=school’ just because a school uses it. So maybe I only should use the ‘highway=raceway’ tag.
例子：
Just started mapping this area. Currently looks uninhabited on the map, but check back later in a few weeks or so, or join me in tracing the area. Mapping areas like this is so much different from mapping in Western Europe where you sometimes wonder if there’s anything to add. It gives a larger sense of accomplishment to ‘discover’ a town or an entire valley compared to drawing in a missing footway.
Mapping southern Gansu Province, China, I’ve encountered dozens of closed walls, in shapes usually square or oval. In some areas, every village has it’s own ‘castle’. So far, the only thing I’ve read about them was this:
“After the fall of the Qing-dynasty, when the country was undergoing an epoch of chaos, the farmers in the area were being constantly terrorized by local warlords and bandit hordes. So they hurriedly erected these fortifications on the highest points in the hills, thus having a safe haven to fall back to in case of an attack.” Source (with a few pictures)
Here is another picture up close. It even seems to be made from rammed earth, which could mean that some of them may be older than they may seem at first sight.
Edit: A kind OSM contributor sent me a link to a documentary about these structures. It’s in Chinese, but with English subtitles.
http://tv.cctv.com/2016/03/22/VIDE2oprFGUUcK44tKYNHfGX160322.shtml
I haven’t had the time to watch the entire documentary, but I got as far as that parts of these structures may be many centuries old.
I wonder if some of them may have already been constructed during the muslim rebellions a few decades earlier.
So far I’ve tagged hem as ‘historic=fort’, ‘barrier=wall’. Use this Overpass query to find them. A few that had noticeable decay have been tagged as ‘historic=ruins’.
If you have more information on these structures I’d be happy to hear so (may also be in Chinese).
