NavInArea
I often get data request for a certain area. Usualy I would use jview
with -navlook to figure out what nav files are in the region of
interest, but when there are lot's of files this is a painstaking
process. AppendNav can dump out the nav within a mapsheet to ascii
lists. However, regions of interest are rarely a nice orthogonal box.
NavInArea will take polygons and decides if there is a nav fix that
falls within the polygon. To do that it uses a nifty point-in-polygon
function I found online.
The polygon file is just a longitude latitude list (so lon's first!).
The polygon is made up by the sequential order of the polygon coords.
This is pretty important otherwise you'll get weird results.
The logic is very straight forward; it will check each nav fix, and
once it has found one it will stop. It is not interested in how many
fixes are within the polygon; just one instance will satifies the test. Of course,
there should be an option of "min number of fixes in polygon"......
Usage : NavInArea
-area JHCImagefile ||
-polygon polygonfile (ascii list lon lat)
(-skip # )
navfile(s)
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Pim, Nov 17, 2011