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

distancesphere() Distance on the earth sphere in meters between two geographic coordinates. Prototype of the DLL function in C++ syntax (attend lower case!): extern "C" __declspec(dllimport) unsigned long __stdcall distancesphere( double nGeoLon1, double nGeoLat1, double nGeoLon2, double nGeoLat2, double *nDistance); Prototype of the DLL function in Visual Objects syntax: _DLL function distancesphere(; nGeoLon1 as real8,; // 8 Byte nGeoLat1 as real8,; // 8 Byte nGeoLon2 as real8,; // 8 Byte nGeoLat2 as real8,; // 8 Byte nDistance ref real8); // 2 Byte as logic pascal:geodll32.distancesphere // 4 Byte The function calculates the distance on the earth sphere between two geographical coordinates and returns it as distance in meters. 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 distancegeo(). The geographic coordinates nGeoLon1 (longitude) and nGeoLat1 (latitude) of the first point as well as the geographic coordinates nGeoLon2 (longitude) and nGeoLat2 (latitude) of the second point must be passed in [degrees]-notation [vggg.ggg] to the function. The result of the distance calculation is returned in the parameter nDistance in meters. The parameters are passed and/or returned as follows: nGeoLon1 Geographic longitude of the first point in [degrees] notation vggg.ggg nGeoLat1 Geographic latitude of the first point in [degrees] notation vgg.ggg nGeoLon2 Geographic longitude of the second point in [degrees] notation vggg.ggg nGeoLat2 Geographic latitude of the second point in [degrees] notation vgg.ggg nDistance Distance between the points in meters as result of the (ref) computation 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. |