DEM overlap check missing

[Rapsodia86]

Hey @forrestfwilliams,

I ran the multirtc twice on two files located in the /multirtc/input directory. Those two files are from different locations: one in Michigan (MI) and the other in North Dakota (ND). First run on the MI file created "dem.tif" within the /multirtc/input, and the following run on ND file apparently used the same "dem.tif" without actually downloading a proper one. It resulted in a geolocation shift. It would be good to add a safety check to be sure that DEM overlaps the SICD file. Thanks!

Left image uses MI's DEM on ND file; right image uses the correct DEM