ROI_PAC processing for Modern Geodetic Methods (Page 2 of 6)

Table of Contents

Building a DEM:

• Before we can process the data, we must first create a DEM. We will use SRTM data for Hector Mine since it is of sufficiently high resolution (30 m in the US) and accurate (< 10 m vertical error).
• Here, we use a perl script written by Noel Gourmelen at the University of Miami and modified locally. Typing mkdemroinew.pl with no additional arguments will give its usage. % mkdir DEM # assuming you are in ~/MGM/HectorMine
% cd DEM
% mkdemroinew.pl -o HectorMine -s 2 W117 W115 34 36 srtm1
#( this can 1-10 minutes depending on internet speeds)

# if all works properly, a gs display of the area DEM will come up
# type 'quit' to exit gs If everything worked you should get a .ps file that looks similar to this.
  
  This may or may not work. We have had modest successes with this because the ftp site the program accesses may be down or too slow. The program will stop if it cannot get the files.
  
  
• A "work-around" would be to separately download the file directly from the site. ftp://e0srp01u.ecs.nasa.gov/srtm/version1/United_States_1arcsec/1arcsec
  The files are zipped, 1^ox1^o blocks and are labeled by their degree of latitude and longitude (e.g. N35W117.hgt.zip).
  Because our range spans 2 degrees in X and Y, we will need 4 files:

              N34W116.hgt.zip
              N34W117.hgt.zip
              N35W116.hgt.zip
              N35W117.hgt.zip
  

• If you have these files locally, you can use the -local flag in mkdemroinew.pl.
• The necessary files are:

             .dem     = dem file for ROI_PAC
  	   .dem.rsc = ascii header file for .dem
             # the following are only needed for GMT plotting
  	   .grd     = netcdf grd file used by gmt for plotting
             .grad    = netcdf illumination gradiant used by gmt for plotting
             .cpt     = color palate file used to color topography within GMT
  	   .ps      = resultant GMT plot that can be seen with gs or gv.
  

• For class, another "work-around" is to copy over (or preferably link) the version created in ~anewman/MGM/HectorMine/DEM/

   % ln -s ~anewman/MGM/HectorMine/DEM ~/MGM/HectorMine/