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don't mix geodetic and geocentric coordinates

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torsten 2009-06-19 11:58:56 +00:00 • committed by Tim Moore
parent 90581f8bf0
commit 40d2925126
1 changed files with 10 additions and 11 deletions
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21
src/Environment/ridge_lift.cxx
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@ -163,25 +163,24 @@ void FGRidgeLift::update(double dt) {
timer -= dt;
if (timer <= 0.0 ) {
// NOTE: this mixes geocentric and geodetic calculations which give mathematically incorrect results
// probably this is acceptable for calculating the ridge lift, converting from
// geodetic to geocentric coordinates is somewhat expensive
// probe0 is current position
probe_lat_deg[0] = _user_latitude_node->getDoubleValue();
probe_lon_deg[0] = _user_longitude_node->getDoubleValue();
probe_elev_m[0] = _ground_elev_node->getDoubleValue() * SG_FEET_TO_METER;
SGGeoc myPosition = SGGeoc::fromDegM( probe_lon_deg[0], probe_lat_deg[0], 20000.0 );
// position is geodetic, need geocentric for advanceRadM
SGGeod myGeodPos = SGGeod::fromDegM( probe_lon_deg[0], probe_lat_deg[0], 20000.0 );
SGGeoc myGeocPos = SGGeoc::fromGeod( myGeodPos );
double ground_wind_from_rad = _surface_wind_from_deg_node->getDoubleValue() * SG_DEGREES_TO_RADIANS + SG_PI;
// compute the remaining probes
for (int i = 1; i < sizeof(probe_lat_deg)/sizeof(probe_lat_deg[0]); i++) {
SGGeoc probe = myPosition.advanceRadM( ground_wind_from_rad, dist_probe_m[i] );
probe_lat_deg[i] = probe.getLatitudeDeg();
probe_lon_deg[i] = probe.getLongitudeDeg();
if (!globals->get_scenery()->get_elevation_m(
SGGeod::fromDegM(probe_lon_deg[i],probe_lat_deg[i], 20000), probe_elev_m[i], NULL )) {
for (int i = 1; i < sizeof(probe_elev_m)/sizeof(probe_elev_m[0]); i++) {
SGGeoc probe = myGeocPos.advanceRadM( ground_wind_from_rad, dist_probe_m[i] );
// convert to geodetic position for ground level computation
SGGeod probeGeod = SGGeod::fromGeoc( probe );
probe_lat_deg[i] = probeGeod.getLatitudeDeg();
probe_lon_deg[i] = probeGeod.getLongitudeDeg();
if (!globals->get_scenery()->get_elevation_m( probeGeod, probe_elev_m[i], NULL )) {
// no ground found? use elevation of previous probe :-(
probe_elev_m[i] = probe_elev_m[i-1];
}