NetNews Usenet Archive 1993 #3/NN_1993_3.iso/spool/comp/infosyst/gis/5031

Internet Message Format | 1993-01-25 | 3.2 KB

Path: sparky!uunet!news.claremont.edu!nntp-server.caltech.edu!anne
From: [e-mail] (Anneliese Lilje)
Newsgroups: comp.infosystems.gis
Subject: Re: where to find USGS elevation data
Date: 25 Jan 1993 20:41:23 GMT
Organization: California Institute of Technology, Pasadena
Lines: 50
Message-ID: <[e-mail]>
References: <[e-mail]> <[e-mail]> <[e-mail]>
NNTP-Posting-Host: sandman.caltech.edu

In article <[e-mail]> [e-mail] (David Mark) writes:
>In article <[e-mail]> [e-mail] (Darrell McCauley) writes:
>>In article <[e-mail]>, Alan Rea <gwdokokl![e-mail]> writes:
>>
>As someone else has recently noted, and as is described in this group's FAQ,
>there is an ad hoc version of what you describe, a sort of digital swap-meet,
>on spectrum.xerox.com [192.70.225.78].  I forget the kind person who set it
>up, but people who had public domain geographic data sets were encouraged to pu
>them there.  As also has been noted here, there is a nice set of specially
>prepared (by Mark Kumler together with folks at USGS Menlo Park) DEMs
>representing all the major physiographic regions of the US, available by
>anonymous ftp from ncgia.ucsb.edu.
>
>The main problem is that for applied work, the researcher needs the DEM of
>their study area.  There are approximately 55,000 USGS 7.5 minute
>quadrangles that form the units for DEMs.  Since these DEMs in their
>raw form are a meg or two, if complete converage could be collected, it
>would be more like 50 or 100 Gigabytes if I am doing the rough math
>correctly.
>
>Personally, I think this is something that USGS itself should do, put all
>their public-domain data on ftp servers.  I also think we will see that in
>the next 4 years, but that is strictly my opinion/prediction and not based
>on any information from USGS.

As someone who has had to suffer for the lack of digital data from the
USGS, I can tell you this is a severe problem. DEM's for many areas
are totally insufficient for work in my area, geology. In particular
geological mapping of the Los Angeles Basin and of course the Landers
Earthquake rupture area. Although some of the DEM's are made from 1:24000
topos, the ones needed for our area are not, and a scale of 1:24000 to
say 1:10000 is ideal for mapping work. At the present time, we order
clear mylars with topolines only from the U.S.G.S and scan them in at 700
dpi. At this resolution gridline in arc info does a great job of
recreating the topos with VERY FEW errors. I have then written an aml
to tag each arc with an elevation. The resulting data models are perfect
for geologic mapping.

I have spoken with several people in the U.S.G.S. including the head
of the present 1:100,000 project (they are putting the 1:100,000 scale
maps on ARC/INFO). As it stands the reason for not getting topos on line
in ARC/INFO or whatever is simply money. They are grossly underfunded.
And that's sad. There is so much geologists could get out of using GIS
if the data were already available in digital form. Sigh. Oh well.


anne