1 // do some test relating to the concept of "up"
7 #include <simgear/constants.h>
8 #include <simgear/math/sg_geodesy.hxx>
11 // for each lat/lon given in goedetic coordinates, calculate
12 // geocentric coordinates, cartesian coordinates, the local "up"
13 // vector (based on original geodetic lat/lon), as well as the "Z"
14 // intercept (for which 0 = center of earth)
20 for ( double lat = 0; lat <= 90; lat += 5.0 ) {
21 cout << "lon = " << lon << " geod lat = " << lat;
23 double sl_radius, lat_geoc;
24 sgGeodToGeoc( lat * DEG_TO_RAD, alt, &sl_radius, &lat_geoc );
25 cout << " geoc lat = " << lat_geoc * RAD_TO_DEG << endl;
27 Point3D pgd( lon * DEG_TO_RAD, lat * DEG_TO_RAD, 0.0 );
28 Point3D pc = sgGeodToCart( pgd );
29 cout << " cartesian = " << pc << endl;
33 sgMakeRotMat4( UP, lon, 0.0, -lat );
34 sgSetVec3( geod_up, UP[0][0], UP[0][1], UP[0][2] );
35 cout << " geod up = " << geod_up[0] << ", " << geod_up[1] << ", "
36 << geod_up[2] << endl;
38 double slope = geod_up[2] / geod_up[0];
39 double intercept = pc.z() - slope * pc.x();
40 cout << " Z intercept (based on geodetic up) = " << intercept << endl;
42 slope = pc.z() / pc.x();
43 intercept = pc.z() - slope * pc.x();
44 cout << " Z intercept (based on geocentric up) = " << intercept << endl;