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| GeoCommunity Mailing List |
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| Subject: | RE: GISList: scale |
| Date: |
09/15/2002 01:09:02 PM |
| From: |
Tomaz Skrbinsek |
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Creating details out of coarse data is a bad habit that shouldn't be
used for educational purposes. :) Anyway, I'm not completely sure what
you want to do here and where is the problem. If I understand this
correctly, you now have a DEM that doesn't fit on your original data. If
this is the case, just georegister the new DEM to your original data and
you're all set. Still, the details you get through such procedure are
quite virtual.
SRTM (Shuttle Radar Topography Mission) data is getting released. I
think that you can get 30 m and 90 m elevation data from NASA for free,
but it is currently available only for the US. They predict that the
whole world will be processed by July 2004, and plan on releasing data
as it is being processed (they have all the data, but is not processed
yet). I'm waiting for this data too and I hope that they won't put some
national security restrictions on it or something like that when it's
finally released.
http://www.jpl.nasa.gov/srtm/
Another thing you can try is finding ASTER DEM data... it used to be
free, but they have started charging for it in August (just read that
when I was looking for addresses for you and am not too pleased). Still
looks quite cheap, though. It has a 30 m resolution and you can find it
at the EOS data gateway, which is a bit obscure but quite useful.
Coverage varies, though, and I have no idea if Guatemala is covered -
you will have to check for yourself. There are some specifics in finding
and using ASTER data, but there is a tutorial on that out there on the
web. I've tried finding it, but I've never used it since the data wasn't
available for the areas I was interested in.
http://spatialnews.geocomm.com/features/childs4/index2.html
http://edcimswww.cr.usgs.gov/pub/imswelcome/
I hope this helps - if you're lucky you might find some of the data you
need, if not now than at least in some sort of a semi-near future.
Cheers,
Tomaz
----------------------------------------------
Tomaz Skrbinsek In an atomic war, all men
bine@kibla.org will be cremated equal
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> -----Original Message-----
> From: John Jacob Matthys [mailto:jmatthys@indiana.edu]
> Sent: Tuesday, September 10, 2002 10:00 PM
> To: gislist@geocomm.com
> Subject: GISList: scale
>
> Hello all
> I am in need of a dem for eastern Guatemala for educational purposes.
> The only info i could get was a level 0 dted of the study area. Level
> 0 data is very coarse (1km) and a more detailed dem is needed for the
> study. SO i converted the dted into a contour line coverage. I then
> adjusted the contour lines and added more incremental contour lines
> based on topo images of the study area. Finally i preformed the
> topogrid function
> (arcinfo) on the contours which takes into account rivers and
sinkholes to
> recalculate the contours into a more detailed dem. This new dem is
more
> detailed, but I need some method to assign a scale to this new dem.
What
> Method should be used to assign a scale to a map, with an unknown
> scale???? ANy suggestions would be greatly appreciated.
> thanks
> jake
>
>
>
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