Thanks Yves, but my question still remains though. So in this raster of 1200 x 1200 pixels, does each pixel get assigned an elevation in meters of "x" meters? Or do the four corners of each pixel have different elevation values of a,b,c and d meters each?
On Sun, Mar 4, 2012 at 8:30 PM, yvecai <yve...@gmail.com> wrote: > ** > It seems to me that the SRTM dataset is available in tiles of 1°x1°, with > a 3 arc second resolution, which gives a raster of 1200x 1200 pixels. 3 arc > second is ~90 meter, but *exactly* 3 arc second in WGS84. > http://dds.cr.usgs.gov/srtm/version2_1/Documentation/Quickstart.pdf > Yves > > Le 04/03/2012 19:36, Ed Linde a écrit : > > Yves, I am not sure I understand what you are saying..sorry. My question > is basically if the points within a single cell can > potentially have different elevation values because of interpolation? Or > do all the points that lie within a cell get one elevation > value? > > On Sun, Mar 4, 2012 at 2:36 PM, yvecai <yve...@gmail.com> wrote: > >> Le 04/03/2012 14:14, Ed Linde a écrit : >> >> Hi All, >> Can someone help me understand a concept with the SRTM raster. My >> understanding is that the raster can be thought of as a uniform grid with >> each cell having dimension = "90m x 90m" (for SRTM-1 dataset). Now I am >> just wondering if the elevation values are 4 values at each vertex or >> boundary point of a cell? or is it one elevation value for the 90x90 m^2 >> area covered by the cell? I ask because if its the first option, then it >> would mean that every point that falls in the cell has it's elevation >> calculated using some sort of interpolation between the 4 corner points of >> the cell to arrive at this point's altitude. Or do several points that fall >> into this 90x90 cell get assigned the same elevation value? >> Would be great if I could get some help understanding this concept about >> SRTM rasters. >> >> Cheers, >> Ed >> >> >> _______________________________________________ >> postgis-users mailing >> listpostgis-users@postgis.refractions.nethttp://postgis.refractions.net/mailman/listinfo/postgis-users >> >> Wouldn't that be a grid of 1°/1201 by 1°/1201 with 1201x1201 elevation >> value? >> Just a guess. >> Yves >> >> _______________________________________________ >> postgis-users mailing list >> postgis-users@postgis.refractions.net >> http://postgis.refractions.net/mailman/listinfo/postgis-users >> >> > > _______________________________________________ > postgis-users mailing > listpostgis-users@postgis.refractions.nethttp://postgis.refractions.net/mailman/listinfo/postgis-users > > > > _______________________________________________ > postgis-users mailing list > postgis-users@postgis.refractions.net > http://postgis.refractions.net/mailman/listinfo/postgis-users > >
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