[GRASS5] New USGS DEM data format

Roger S. Miller rgrmill at rt66.com
Wed Aug 1 21:26:03 EDT 2001

Rich Shepard wrote:

>   I just learned that the US Geological Survey (USGS) has done two things
> less than desirable. First, they no longer provide data for free, especially
> the 30-m DEM data. It's only available now at one commercial site, that of
> GeoComm (URL avaialable upon request).

Where did your information come from?  They haven't done that yet, and I
don't see any evidence on their site that they intend to ever do that.

The web site at http://edcwww.cr.usgs.gov/webglis appears to offer all
of the same elevation data that it always did, including the 2
arc-second (30-minute) DEMs.  I would check with Earthexplorer
(http://earthexplorer.usgs.gov) as well, but I can't.  They keep
threatening to take webglis down and force all traffic through
earthexplorer, which would be unfortunate.  I have never gotten
EarthExplorer to work right.
>   Second, and more importantly, they have changed the format of the
> elevation data within the DEM to "decimal meters" which I assume to be
> fractional meters. The elevations used to be only in integral feet or
> meters. So, on this basis, more accurate DEM data is a Good Thing. 

I would be surprised if they added any accuracy by changing the file
format.  In fact, I would be surprise if they changed the file format on
anything they already released in an older format.  They put out new
digital map data all the time (especially in the 7.5 minute series). 
Perhaps they are using a new format for the newly released data?

Roger Miller

More information about the grass-dev mailing list