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 local program that pulls data from a local archive of SRTM data in order to create a netCDF (gmt-style) grid file
for the region of interest. Typing srtmgrd
with no additional arguments will give its usage.
% mkdir DEM # assuming you are in ~/MGM/HectorMine
And old program mkdemroinew.pl may also work to pull data from the internet and do everything you need. In addition, others
have written their own codes. Given that we have SRTM data locally, our codes should work best here.
% cd DEM
% srtmgrd -R-117/-115/34/36 -E1 -GHM.grd
#( this can take a while depending on the size of region you need)
- Now we must create a format of this DEM that is usable by roipac using grd2rsc.
% grd2rsc HM.grd
- Lets now look at the grd files using GMT:
% gmtset PAPER_MEDIA letter BASEMAP_TYPE plain HEADER_FONT_SIZE 20 LABEL_FONT_SIZE 14 PLOT_DEGREE_FORMAT D D_FORMAT %12.2f
If everything worked you should get a .ps file that looks similar to this.
% grdgradient HM.grd -A0/270 -GHM.grad -Ne0.6
% grd2cpt HM.grd -Crainbow > color.cpt
% grdimage HM.grd -IHM.grad -P -X3 -Y4 -Ccolor.cpt -R-117/-115/34/36 -JX15 -B.5a.25g.5WeSn >HM_DEM_color.ps
# or Gray
% echo "0 220 10000 220 " > gray.cpt
% grdimage HM.grd -IHM.grad -P -X3 -Y4 -Cgray.cpt -R-117/-115/34/36 -JX15 -B.5a.25g.5WeSn >HM_DEM_gray.ps
- We can also look at it using mdx.pl (only certain machines):
% mdx.pl HM.dem # tested while logged into PELE
- To perform the interferograms we will need to have a local DEM directory with the following files in our processing directory. 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/