zed писал(а):Так какой же это SRTM 3, если сделан неизвестно из чего и неизвестно кем (шарашкина контора дяди Васи и Ко)?
Цитирую:
SRTM data, in HGT format, can be downloaded from here, but for some mountain areas there are no-data (void) cells, and there are no SRTM data north of 60°20'N. For the tiles here, the majority of SRTM mountain no-data void areas have been filled from the best available alternative sources
Alternative Sources
Topographic Maps: YES For mountainous areas, the best alternative sources are detailed topographic maps, preferably based on material collected from ground surveys. These are many and various. The best general source is the Russian military. Their maps cover most of the world at 200k and much of the world at 100k. The contours on these are correctly placed, with very few exceptions. In some places there are elevation inaccuracies but these are often shown up by surrounding SRTM data and other sources and have been adjusted for. Most 7000m summits are covered by more accurate topos, e.g. Finnmaps of Nepal, Chinese Snow Maps and maps from various German sources. 250k JOG topos from the US military cover much of the world, but most of these have not been released, and the topographic quality of their AMS predecessors is very poor.
Spot elevations on Sketch Maps: YES Some elevations on some Japanese Alpine Club sketch maps covering most of the Chinese Eastern Himalayas that top 6000m were taken from Chinese military maps and were very helpful. But elsewhere in the Eastern Himalaya amd in some parts of the Indian and Chinese Western Himalaya, there are significant uncertainties.
Landsat images: YES In some areas, where I have found insufficient reliable topographic map detail, I have been consulting the shading on Landsat and other imagery used by Google Earth, and finding it to be helpful. More recently (summer 2008) I have using Landsat images more directly by reprojecting them geographically and using them as supplementary underlay. The results were surprisingly helpful, even though Landsat contains no elevation data. Landsat imagery is very accurate and its shades accurately match SRTM generated contour patterns.
GTOPO30 and GLOBE30: NO Even if the resolution of this source were adequate for mountain areas, which it is not, the quality of some of this is such that it is not unusual for two summits separated by 2km and a drop of 600m to show up as single summits. There may be good DTED Level 1 data (resolution 3", based on 250k maps) for some areas, but outside the US this has not been generally released by the US military.
ASTER GDEM: Yes, in some areas uploaded or updated since July 2009. For my general comments about this source, see my detailed review.
Т.е. этот сервис ничто иное, как народная солянка (не спорю, что при всём при этом он может быть весьма полезен), но у SRTM таки нету данных севернее 60 градусов.
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