asking for a lot of grass advice

GRASS GRASS user
1

Hello,

A long-time lurker appears and needs help…

I am considering developing a package that will calculate signal reception for specific stations using the Longley Rice Irregular Terrain Model. I need vector-topo data for the entire country.

  1. What are my options this data? I suppose that I should use the DEM data from USGS?

  2. Are there C or Perl libraries for working with DEM’s? Specifically, to use Longly Rice, I have to resample the vector data to generate an elevation profile between two arbitrary points from the vector-topo data. Any ideas on that either?

  3. When I am done I my data will be ,< lat>,; which I plan on treating as a height field. What Grass tools can I use to create an image from height field data.

  4. Also, are there any books out there to jumpstart someone who knows things like MapInfo, and Linux, but not Grass??

Any input from the group is very much appreciated.

Thanks in advance,
Robb

2

Hi Rob,

My answers are below your questions. However, if you like, go ahead and
give me a call at the office. We worked with a couple of very similar projects
to the one I think you are describing. My number is 254-710-6814

Bruce

–
Bruce Byars
Hydrologist and Senior Research Scientist
CAGSR - GRASS Dev. Team - Baylor University

I am considering developing a package that will calculate signal reception for specific stations using the Longley Rice Irregular Terrain Model. I need vector-topo data for the entire country.

First, do you have to use vector data? Can you use rasters and then script up r.mapcalc,
r.los, and r.binfer to perform your analysis? Raster data may be easier to work with from
your description. Vector topo map for the entire country will be BIG. Gigabytes. We already
have the US DEM’s assembled, rectified, and cleaned up and at 90m grid resolution the DEM
is about 2 gigabytes (raster data…I’ll calcualte the vector for you tomorrow).

-------------------------------------------------------1. What are my options this data? I suppose that I should use the DEM data from USGS?

You can produce vector data from the USGS DEM data without any problem using the
r.poly tool.

------------------------------------------------------------------------------------ 2. Are there C or Perl libraries for working with DEM’s? Specifically, to use Longly Rice, I have to resample the vector data to generate an elevation profile between two arbitrary points from the vector-topo data. Any ideas on that either?
Personally, I think you will be better off cutting raster transects. Tools are already in GRASS
to do this.

  1. When I am done I my data will be ,< lat>,; which I plan on treating as a height field. What Grass tools can I use to create an image from height field data. You can create a raster “elevation” map of your surface with no problem. To create
    nice visualizations, use NVIZ or possibly d.3d
  1. Also, are there any books out there to jumpstart someone who knows things like MapInfo, and Linux, but not Grass??

We have a brand new tutorial that will be ready this week.