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## Re: [TowerTalk] terrain profile algorithm

 To: towertalk@contesting.com Re: [TowerTalk] terrain profile algorithm Jim Lux Sat, 16 Jun 2012 10:18:25 -0700 mailto:towertalk@contesting.com>
 On 6/16/12 9:55 AM, Ian White GM3SEK wrote: > Jim Lux wrote: >> I'm looking for an algorithm for my "generate all profiles for HFTA" app.. >> I've taken a couple trivial shots at this, but I'm pretty sure someone >> out there knows of a "better way". >> >> here's what I want.. >> >> I have an array of heights vs distance at fairly close post spacings (on >> the order of 10 meters) maybe 1000 points or so, representing the >> profile along a particular radial. What I want to do is "compress" that >> into about 100 or so segments that are connected (e.g. HFTA input). >> That is, I want to convert that to a series of x,y coordinates connected >> by straight lines that "adequately" represents the terrain. >> >> I started with a simple "if the adjacent point is within X meters in >> altitude, then collapse the two into one", but that produces profiles >> that somehow don't look right (and I can't say much about their HFTA >> fidelity). If the underlying terrain were a ziggurat or mesas with >> valleys, it would probably work, but it turns a gentle slope into a >> staircase. >> >> This is a classic problem in cartographic generalization, and, as it >> happens, this kind of profile is well represented by a fractal, but not >> that this helps me much. I was hoping that someone out there knew of a >> clever way to do it. >> >> Preferably in Python, since that's what I've written everything else in, >> but I can convert anything.. so if you have one written in COBOL, that's >> fine. >> _______________________________________________ > > If may be easier than you think, because HFTA already makes a linear > extrapolation between data points, regardless of horizontal separation. Does it? or does it treat each segment as a flat plate a'la the paper by Breakall, et al. If it were doing a raytracing physical optics approach, then yes, you'd cast the ray to the point of intersection with the surface, figure out the angle, determine the reflection, and move on. But I seem to recall that HFTA does something more like GTD. _______________________________________________ _______________________________________________ TowerTalk mailing list TowerTalk@contesting.com http://lists.contesting.com/mailman/listinfo/towertalk
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