[GRASSLIST:2294] Re: Import questions

Rich Shepard rshepard at appl-ecosys.com
Tue Aug 7 09:42:15 EDT 2001

On Tue, 7 Aug 2001, Kevin Slover wrote:

>     I am trying to figure out the best way to import elevation data at
> this time.  I have finally managed to get grass running, and import some
> OrthoPhotos, but have yet to be able to get elevation data in yet.  I am
> working with several different formats, depending on how much resolution
> I am looking for.  I am working with for right now 1:250,000 DEM from
> USGS and Lidar data in two separate formats.  The DEM is in the native
> format, and the Lidar data at this time is in X,Y,Z.  I have actually
> gotten a raster image from DEM import, but it is definitely not correct,
> as it is a single line in the middle of the display window.  The x,y,z I
> have no clue, as there is no form of ASCII import.  Is there a simple
> command to import these??


  I'm not sure what the native DEM format is, but there is a module called
m.dem.extract that I understand works with data files on disk as well as on
tape. r.in.ascii should take your Lidar data and make a DEM out of it.

> Second question, more on the capabilities of grass, as I am new to the
> environment.  What type of resolution can you import without having it
> take hours to process.  The Lidar data that I am working with is binned
> at 5m, but it would be nice to have finer resolution for what I am
> wantig to do.  I am not working with a great machine, a DELL Server with
> a 500MhZ (?) single processor and 512MB RAM on RH7.1.  I am using the
> precompiled libraries at this point in time.  Thanks for your help....

  I'm working now with 10m DEMs and I have 15 adjacent quads patched
together. My system is a PII/333 with 327M RAM and the processing speed is
acceptable. I don't know where the speed bottleneck may be, but with a lot
of data it may be disk access.



Dr. Richard B. Shepard, President

                       Applied Ecosystem Services, Inc. (TM)
            2404 SW 22nd Street | Troutdale, OR 97060-1247 | U.S.A.
 + 1 503-667-4517 (voice) | + 1 503-667-8863 (fax) | rshepard at appl-ecosys.com
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