drmap

drmap is a program for generating amateur-radio-related maps from USGS National Map data. From the description in the source code, with graphics added inline:

    drmap
      -ant  <antenna height>
     
        The height of the antenna. If -imperial is present, the height is in feet, otherwise it is in metres.
     
      -call <callsign>
     
        The callsign associated with the plot. Must be present.
       
      -cells <number of cells>
     
        The number of cells from the centre of the plot to the edges. The default is 3/8 of the width of the plot, in pixels. For the default width of 800, the value is therefore 300.
       
      -datadir <directory>
     
        The directory that contains USGS GridFloat tiles
       
      -elev
     
        Create an elevation plot: the plotted values are the elevation of each cell as seen from the antenna. Most are therefore negative.
       
      -grad
     
        Create a gradient plot: the plotted values are the gradient of the terrain in the direction from the QTH.
       
      -hzn [distance limit]
     
        Plot the elevation of the horizon around the periphery of the figure. Eye-level is set in the same way as eye-level for the -los option. Only distances out to the distance limit are used in this calculation. If the distance limit value is not present, it is assumed to be the same as the radius of the figure.
       
      -imperial
     
        Use imperial units instead of metric. That is, miles instead of kilometres and feet instead of metres. Applies both to values on the command line and to values on the output plot(s).
       
      -lat <latitude>
     
        Latitude in degrees north. If present, -long should also be present.
       
      -long <longitude>
     
        Longitude in degrees east. If present, -lat should also be present. Note that because the USGS data covers only the US, longitude should be negative; but if it is positive, the program will negate the value before use.
       
      -los
     
        Create a line-of-sight plot in addition to the standard height-field plot. Eye-level is assumed to be 1.5m or 5 feet, unless the -ant option is presewnt, in which case eye-level is the same as the height of the antenna.

      -outdir <directory>
     
        The directory into which the output maps should be written
       
      -radius <distance1[,distance2[,distance3...]]>
     
        One or more radii for the plot(s), in units of km unless -imperial is present, in which case the units are miles.
       
      -qthdb <QTH database filename>
     
        A file linking QTH information to callsigns. Each line of the file should contain three entries pertaining to a station, separated by white space: the callsign, the latitude and the longitude. This database will be used only if one or both of the -lat and -long parameters is missing from the command line.
       
      -sm
     
        USGS tiles are each about 450MB in size. This parameter ("small memory") tells drmap to use the disk files that contain the tiles as-is, rather than moving them into RAM where their contents can be accessed much more quickly. Using this parameter therefore slows access, but means that there is essentially no limit to the number of tiles that may be used to build a plot. drmap automatically stops loading tiles into RAM when there is less than about 500MB of free RAM and switches to using the tiles on disk, so ordinarily there is no need to worry about whether to use the "-sm" parameter. This parameter will be removed in  future versions of drmap if it seems to be unneeded in practice.
       
      -width <pixels>
     
        width, in pixels, of the plot(s). The default is 800. The height is automatically set to be three quarters of this value.
       
    Examples:
      drmap -call n7dr -datadir /zfs1/data/usgs/drmap -outdir /tmp/drmap -qthdb ~/radio/qthdb -imperial -ant 50 -radius 2 -los -hzn 5
     
        Look up the call "n7dr" (case is ignored) in the file "~/radio/qthdb". Each line in that file is of the form:

        <callsign>     <latitude>     <longitude>
       
        In particular the following line appears in that file on my system:

        N7DR        40.108016   -105.051700
       
        The latitude and longitude information for N7DR are extracted from that file.
       
        The program will look for relevant USGS files in the directory "/zfs1/data/usgs/drmap". If it fails to find any needed files, it will download them from the USGS and place them in that directory prior to using them.
       
        The program will write output plots in the directory tmp/drmap.
       
        The program will use imperial units (miles and feet), and assume an antenna 50 feet above ground.
       
        It will generate a height plot displaying a radius of 2 miles around the N7DR QTH:

       
        It will also create a line-of-sight plot (showing the terrain visible from the putative antenna, 50 feet above ground level):

        
        In both plots, the elevation of the horizon as seen from 50 feet above ground level is drawn around the periphery. The program assumes that no contribution to the horizon is more than five miles from the QTH. It also (always) calculates and displays the M[ean] H[eight] A[bove] T[errain] of the antenna for the area inside the provided radius.

      drmap -call RMNP -datadir /zfs1/data/usgs/drmap -outdir /tmp/drmap -lat 40.441358 -long -105.753685 -radius 1
     
        Create a plot for the point 40°.441358N, 105°.753685W (which is in Rocky Mountain National Park).
       
        The program will look for relevant USGS files in the directory "/zfs1/data/usgs/drmap". If it fails to find any needed files, it will download them from the USGS and place them in that directory prior to using them.

        The program will write output plots in the directory tmp/drmap.
       
        The program will use metric units (kilometres and metres).
       
        It will generate a height plot displaying a radius of 1 kilometre around the designated location:

      drmap -call RMNP -datadir /zfs1/data/usgs/drmap -outdir /tmp/drmap -lat 40.441358 -long -105.753685 -radius 10 -los -hzn 5 -grad -elev
   
        Create a plot for the point 40°.441358N, 105°.753685W (which is in Rocky Mountain National Park).
       
        The program will look for relevant USGS files in the directory "/zfs1/data/usgs/drmap". If it fails to find any needed files, it will download them from the USGS and place them in that directory prior to using them.

        The program will write output plots in the directory tmp/drmap.
       
        The program will use metric units (kilometres and metres).
       
        It will generate a height plot displaying a radius of 10 kilometres around the designated location:

       It will also generate a line-of-sight plot, assuming the default eye level of 1.5m:

       
        It will also generate a gradient plot, showing at each point the gradient measured in a direction from the centre of the plot to that point:

        It will also generate an elevation plot (reminiscent of 1960s tie-dye), showing at each point the elevation angle measured in a direction from the centre of the plot to that point:

        In all these plots, the elevation of the horizon as seen from eye level is drawn around the periphery. The program assumes that no contribution to the horizon is more than five kilometres from the QTH.