* Val Kartchner <val...@gmail.com> [2011-02-16 20:13 -0700]: > What I'm asking about is this anomaly in the area of Sevier Lake: > "http://www.openstreetmap.org/?lat=39.0035&lon=-113.0895&zoom=14&layers=C";. > What is up with this sudden change in terrain?
The OpenCycleMap elevation data comes from the SRTM dataset, which was obtained by taking stereoscopic images from the Space Shuttle. There are all sorts of things that interfered with the data capture in individual locations, from highly-reflective things (like snow-covered mountain peaks) preventing their elevation from being determined, to the fact that the elevation data is treetop- or buildingtop-level, not ground level, to inexplicably large holes in the data (see http://flic.kr/p/82QGk7 ). My guess would be that this region's data was recorded in two passes and there was a dust storm or something that looked to the shuttle like a hill. Note that TopOSM, which uses the USGS National Elevation Dataset, doesn't show anything there (probably because NED is clipped to the surface of bodies of water): http://toposm.com/us/?lat=39.0035&lon=-113.0895&zoom=12&layers=B0TT (TopOSM also shows a lot of intermittent streams from the USGS National Hydrography Dataset.) -- ...computer contrarian of the first order... / http://aperiodic.net/phil/ PGP: 026A27F2 print: D200 5BDB FC4B B24A 9248 9F7A 4322 2D22 026A 27F2 --- -- You step in the stream, but the water has moved on. This page is not here. ---- --- -- _______________________________________________ Talk-us mailing list Talk-us@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk-us
