Hi Janet, Tthe data seems to be in a geographic (angular) coordinate system, which means that you won't be able to get resolution in meters. Due to the curvature of the Earth's surface, one arc second has a different length at different latitudes. That's exactly what you're seeing in your example - 0:00:01 means 0° 0" 0'. The notation is in degrees minutes seconds (DMS) rather than decimal degrees (DD), which I prefer, but however you look at it, unless you reproject the data into a projected coordinate system like UTM, etc., the resolution will be in that unit.
The short version of that long story is that your data sounds like it's fine - 1 arc second is about 30m and so it looks like you've got the data you wanted and GRASS interpreted it correctly. Best, Daniel -- B.Sc. Daniel Lee Geschäftsführung für Forschung und Entwicklung ISIS - International Solar Information Solutions GbR Vertreten durch: Daniel Lee, Nepomuk Reinhard und Nils Räder Softwarecenter 3 35037 Marburg Festnetz: +49 6421 379 6256 Mobil: +49 176 6127 7269 E-Mail: [email protected] Web: http://www.isi-solutions.org 2012/8/8 Janet Choate <[email protected]> > Hi all, > this seems silly, but i am a bit confused as haven't had this be an issue > before. i downloaded data from USGS NED (they have changed the process > since i last used). i requested data at 1 arc second (which is supposed to > be approx 30 meters) > > i set up a new grass dataset, reading the projection and datum terms from > a georeferenced data file (referring to the w001001.adf file). at the 'set > default region extent and resolution' page, the correct N/S/E/W coordinates > are shown, however, the N-S & E-W resolution are set to 0.000277777777841. > it would not let me change the resolution. accepted and set the region. > then used r.in.gdal to import the raster (the w001001.adf file), then set > the region to the new dem raster and displayed it. so all seemed to work > fine. however, when i check the region settings with g.region -p, the > nsres/ewres are 0:00:01. > i need this to be a 30 meter DEM, and am confused as to what the present > resolution actually is, as i requested 30m (1 arc second) at download from > NED. > anyone have any tips regarding this? > > thank you, > Janet > > > _______________________________________________ > grass-user mailing list > [email protected] > http://lists.osgeo.org/mailman/listinfo/grass-user > >
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