My approach would be (as always) to reuse existing programs. Most prediction programs allow you to limit the elevation, and they do take care of the ellipsoid. Since you probably want to predict the entire constellation over long intervals, a text file capable program is needed. I prefer Rob Matson's SkyMap, which has excellent accuracy and capabilities in graphic mode, but has a text output in one-degree accuracy. Mike McCants' HighFly is another alternative. I have used his LEO counterpart QuickSat to find which satellites ARE visible in Greece a particular week, that are NOT visible at a reasonable elevation and/or magnitude from Sweden in one year. To process the text output I use a powerful text editor, www.ultraedit.com/ , to preprocess the outputs. If I do need to filter the output further, I write a simple program. I'll send you a simple sample in the weekend, and more if you believe it's the right approach. /Björn >I'd like to calculate some visibility statistics for the GPS >constellation. This means, I'd take my ephemerides files, or something >of the kind, for the constellation, and then test if there is a line of >sight between any satellite and a ground station. Eventually, I'd have >to make provision for limiting the elevation angle, and for using the >elipsoid (or geoid) rather than a sphere. Finally, I'd want to check if ------------------------------------------------------------------------- Subscribe/Unsubscribe info, Frequently Asked Questions, SeeSat-L archive: http://www.satobs.org/seesat/seesatindex.html
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