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Additional Exercises

Creating a Topographic Image

This example utilizes DEM topography data 5 minute topography data to create a topographic image that may be used as a basemap.

For this exercise you will need to download the DEM global 5 minute topography file world_topo.5min to your working directory.

  1. Create a topographic grid for desired area using GDTOPO

     GDFILE   = nam_basemap.gem
     GAREA    = 10;-140;65;-40
     GDATTIM  = 070101/0000
     GVCORD   = none
     GFUNC    = topo
     TOPOFL   = world_topo.5min
     IJSKIP   = 0
     GEMPAK-GDTOPO>r
    
  2. Create an image from topography/bathymetry data using GD2IMG

    Use a 2 part calibration range for band 3.

    Use pixel values 0 to 7 for negative values (-8103 to 0 meters), and pixel values 8 to 95 to represent positive values (0 to 4700 meters).

    The region selected represents a 6 km resolution product.

     GDATTIM  = last
     GDFILE   = nam_basemap.gem
     GLEVEL   = 0
     GVCORD   = none
     GFUNC    = topo
     SCALE    = 0
     PROJ     = str/90;-97;0
     GRDAREA  = 15;-116;50;-51.95
     KXKY     = 1002;925
     CPYFIL   =  
     SATFIL   = nam_basemap.gini
     CALINFO  = 99/3/TOPO,0,7,-8103,0;8,95,0,4700
     WMOHDR   = TICZ99/UPC/
     GEMPAK-GD2IMG>r
    
  3. Display the composite image in GEMPAK programs as a satellite image and overlay data as desired.

     MAP      = 1
     GAREA    = dset
     PROJ     = sat
     SATFIL   = nam_basemap.gini
     LUTFIL   = upc_dem5.tbl
     GEMPAK-GPMAP>r
    

image

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