Prototype and description of the function point2pointsphere() (Function of the unlock requiring group "Distance calculations") |

point2pointsphere() Calculation of a destination point on the earth sphere by given start point, bearing and distance. Prototype of the DLL function in C++ syntax (attend lower case!): extern "C" __declspec(dllimport) unsigned long __stdcall point2pointsphere( double nGeoLon1, double nGeoLat1, double nDistance, double nAzimut, double *nGeoLon2, double *nGeoLat2) Prototype of the DLL function in Visual Objects syntax: _DLL function point2pointsphere(; nGeoLon1 as real8,; // 8 Byte nGeoLat1 as real8,; // 8 Byte nDistance as real8,; // 8 Byte nAzimut as real8,; // 8 Byte nGeoLon2 ref real8,; // 4 Byte nGeoLat2 ref real8); // 2 Byte as logic pascal:geodll32.point2pointsphere // 4 Byte The function calculates the geographic coordinates of a destination point on the earth sphere. The calculation uses the geographical coordinates of a start point, its forward bearing (azimuth) and the distance in meters between the points. For the earth surface a sphere with the radius 6371.221 km is taken as basic. Since the function does not consider the ellipsoidal surface of the earth, inevitably a minimum deviation from the exact distance results. More exact results are reached by much lower calculation speed with the function point2pointgeo(). The geographic coordinate nGeoLon1 (longitude) and nGeoLat1 (latitude) of the start point as well as the forward bearing nAzimut from the start point to the destination point must be passed in [degrees]-notation [vggg.ggg] to the function. The bearing must be in the range of 0 up to 360 degrees, where 0 degrees points north and 90 degrees points east. The distance between the points must be passed as meters by the parameter nDistance. The function returns as results the geographic coordinates nGeoLon2 (longitude) and nGeoLat2 (latitude) of the destination point in [degrees]- notation [vggg.ggg]. The parameters are passed and/or returned as follows: nGeoLon1 Geographic longitude of the start point in [degrees] notation vggg.ggg nGeoLat1 Geographic latitude of the start point in [degrees] notation vgg.ggg nDistance Distance between the points in meters on the earth phere nAzimut Forward bearing from point 1 in direction to point 2 in [degrees] notation ggg.ggg nGeoLon2 Geographic longitude of the destination point in [degrees] notation (ref) vggg.ggg as result nGeoLat2 Geographic latitude of the destination point in [degrees] notation (ref) vggg.ggg as result returnVal In case of an error the function returns FALSE, otherwise TRUE. For geographic coordinates in [degrees] notation applies: v Optional sign for longitudes west of Greenwich and latitudes south of the equator. g degrees and decimal fraction of a degree. Unlocking This function is a component of the unlock requiring function group "distance calculations". It is unlocked for unrestricted use together with the other functions of the group by passing the unlock parameters, acquired from the software distribution company, trough the function setunlockcode(). Without unlocking only a few function calls for test purposes (shareware principle) are possible. |