[GRASS-user] COGO along a slope

Manuel Gimond mgimond at colby.edu
Mon Feb 26 15:13:45 EST 2007

Is there a module (or an easy solution) that will generate line 
features from along-terrain COGO data and a DEM?
m.cogo will generate [X,Y] values from COGO data, but it assumes that 
the COGO distance measurements have been projected onto a horizontal 
surface. The only work around I can think of requires computing slope 
data (from a DEM for instance) to get at an average cosine of the 
slope underlying each COGO line segment, then correct the COGO 
distance to get its projected counterpart. For instance, an 
along-terrain distance on a 45 degree slope of 100.0 meters should 
translate to a distance of 70.7 meters on a projected plane. This 
correction can be tedious if manually computed by hand (especially 
since multiple iterations may be needed to compute the average slope 
along a line segment). Any ideas?


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