A question of geometry

[desertdweller]

Here is an interesting question. Are the elevations given in the installation menus, assuming sea level? I am guessing that at higher altitudes (here in Southern Calif) that a bird might appear lower in the Southern sky? I am talking 2000 to 2500 feet elevation.

[sagirma]

hello desertdweller,

Well since geo sattelites are at roughly 120384000 feet altitude above the equator, so 2500 of 120384000 is like 1/49000, so I cant see that is gonna make much difference in your elevation or latitude setting.. this is only my speculation on the matter.

[N4ST]

Originally Posted by desertdweller

Here is an interesting question. Are the elevations given in the installation menus, assuming sea level? I am guessing that at higher altitudes (here in Southern Calif) that a bird might appear lower in the Southern sky? I am talking 2000 to 2500 feet elevation.

It's really a matter of what your elevation angle is to the satellite. The lower the elevation angle, the greater the difference in altitude will make. If you were under the satellite it wouldn't matter how high you were. If we take a simple case of a satellite due south of your location and with an elevation of 45 degrees (assuming a latitude of ~ 38d50m) then going from 0-ft elevation to 2500-ft elevation would be the same as changing your latitude by 2500-ft. The difference in elevation angle is less than 0.1 degree. Now if you were at 81 deg latitude... the math hurts my head, but I think it correpsponds to about 1.1 degree difference in elevation angle. Close to the worst case.

[elgemcdlf]

1/49000 of a foot? That is some serious mileage .000244898 of an inch