There is so much variability in the footprint that #1 or #2 would probably suffice. Working satellites on the fringes of AOS and LOS wheigh heavily on your location, surroundings, and equipments that it's impractical, it's just a visual "references" that shows relative satellite reception.
Hope this helps. - Brent, KB1QD On Mon, Mar 25, 2013 at 11:15 AM, Joseph Armbruster < [email protected]> wrote: > > I can not decide how to implement ground footprints with my google earth > satellite tracker. I figured, since I can't make up my mind, I should get > a second (and third, and fourth) opinion. For this thread, I would like to > discuss how satellite ground-footprints should be implemented. A quick > brainstorm led me to three possible implementations (I am leaning towards > 3). For each of these, I assume that a geographic line-of-sight footprint > is desired with no RF characteristics taken into consideration: > > option 1 : assume a spherical earth model and project a polygon downwards > towards the footprint > > - note: this is obviously the easiest approach but will result in the most > error > > option 2 : assume an ellipsoidal earth model and project an irregularly > shaped polygon downwards towards the footprint > > - note: this is arguably more difficult than option 1 and would result in > less error > > option 3 : use a digital elevation model and an ellipsoidal model to > cull-out regions that are not visible due to geographic features and > project an irregularly shaped polygon downwards towards the footprint > > - note: In this case, our footprint polygon would have holes cut out for > the regions that are culled out by mountain ranges, canyons / etc... > Obviously, this would be the most difficult to implement but would likely > be the best visual representation. The problem is, I would never dream of > distributing DEMs for the entire Earth with my tool, even DTED0 would be > absurd in my opinion. I could make the elevation queries accessible using > a web-service, but then the user would be tied to the internet. The other > option would be to allow the users to download their elevation data into a > cache, then the tool would just load / use it. This way the user would > only have to obtain the elevation data for their region of interest. Maybe > that would be the best approach? I am open to suggestions! > > If you have any experience visualizing footprints, please let me know. I > would be interested in hearing your lessons-learned. These are what the > line-of-sight indicators look like right now: Google Earth Satellite > Tracker - Line of Sight Update > > I am open to comments and suggestions, > Joseph Armbruster > _______________________________________________ > Sent via [email protected]. Opinions expressed are those of the author. > Not an AMSAT-NA member? Join now to support the amateur satellite program! > Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb > _______________________________________________ Sent via [email protected]. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
