[GRASSLIST:2605] Re: Extracting transects from sites

Hamish hamish_nospam at yahoo.com
Fri Feb 13 20:17:39 EST 2004


> I have a huge sites list derived from side-scan sonar data. There are
> millions of UTM coordinate pairs and their corresponding depths.
> 
> I'm going to interpolate this dataset but I want to extract some
> transects from 'real' data to cross-examine to grid derived data.
> 
> In a few words, I need to extract all (x,y,z) triplets from my sites
> file that lies along a dozen lines and are not farther than 100 meters
> from this line.
> 
> Does anybody have any clue?


In GRASS 5.7, make a vector line (either by hand with v.in.ascii, or
s.in.ascii->v.digit to connect the dots), run 'v.buffer buffer=100',
then [v.select, v.extract, or 'v.overlay op=and' ??] to extract only 
points within the buffer.

Not sure how to do it in 5.0 or 5.3, maybe after creating the vector
line use v.to.rast and r.buffer. Then use the r.buffer map as a MASK, 
maybe by modifying s.out.ascii somehow?


good luck,
Hamish




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