Prototype and description of the function getrefsys() (Function of the unlock requiring group "Parameter determination") |

getrefsys() Determination of the transformation parameters for the Reference System Transition between the geodetic source and target Reference Systems. Prototype of the DLL function in C++ syntax (attend lower case!): extern "C" __declspec(dllimport) unsigned long __stdcall getrefsys( unsigned short wRefSysQ, unsigned short wRefSysZ, unsigned short wCoordSysQ, unsigned short wCoordSysZ, char **pszRefSys, unsigned long lForBack); Prototype of the DLL function in Visual Objects syntax: _DLL function getrefsys(; wRefSysQ as word,; // 2 Byte wRefSysZ as word,; // 2 Byte wCoordSysQ as word,; // 2 Byte wCoordSysZ as word,; // 2 Byte pszRefSys ref psz,; // 4 Byte, char**, 1200 alloc. lForBack as logic); // 4 Byte as logic pascal:geodll32.getrefsys // 4 Byte The allocation of memory for "ref psz" / "char**" is necessary only if setstringallocate(FALSE) is called before. The function returns the transformation parameters for the Reference System Transition fitting to the geodetic source and target reference systems wRefSysQ and wRefSysZ as formatted text in the parameter pszRefSys. The text is returned in the language set by the function setLanguage() before. The parameters are passed and/or returned as follows: wRefSysQ Geodetic source Reference System. The available reference systems are specified in the list "Coordinate and Reference systems". wRefSysZ Geodetic target Reference System to which coordinates of the source Reference System has to be transformed. The available Reference Systems are specified in the list "Coordinate Reference Systems". wCoordSysQ Source Coordinate System. It is needed only if for the source or target Reference Systems the identification 1100, 1150 or 1200 (no Reference System Transition) is passed, in order to indicate the used standard ellipsoid. In addition it is needed, if for the source Reference System the identification 0 (standard Reference System) is passed, in order to indicate the standard Reference System that is fitting the coordinate system. The available Coordinate Systems are specified in the list "Coordinate Reference Systems". wCoordSysZ Target Coordinate System. It is needed only if for the source or target Reference Systems the identification 1100, 1150 or 1200 (no Reference System Transition) is passed, in order to indicate the used standard ellipsoid. In addition it is needed, if for the target Reference System the identification 0 (standard Reference System) is passed, in order to indicate the standard Reference System that is fitting the coordinate system. The available Coordinate Systems are specified in the list "Coordinate Reference Systems". pszRefSys The transformation parameters will be provided together with (ref) their descriptions in a formatted text and returned by reference. The lines of the text are separated with "Return and Linefeed". Note: "ref pszRefSys" corresponds to "char**" in C. 1200 bytes of memory for the zero terminated string must be allocated with dependence to the call of the function setstringallocate(). Please consider the notes in the description of the function setstringallocate(). lForBack Flag for the representation of Seven Helmert parameters. An explanation of the Forward and Backward Transformation can be found below. TRUE: The seven parameters of the Helmert transformation are each presented separately for the Forward Transformation from the source system to WGS84 and for the Backward Transformation from WGS84 to the target system. FALSE: The seven parameters of the Helmert transformation are added from the parts Forward Transformation and Backward Transformation. They are valid directly from the source to the target system and are presented together. User defined Reference System Transitions are always shown in this format. returnVal In case of an error the function returns FALSE, otherwise TRUE. GeoDLL calculates Reference System Transitions with Helmert transformation parameters as Forward and Backward Transformations. With a Forward Transformation, starting from the source system, first the rotations and then the translations are performed. With a Backward Transformation, leading to the target system, in reverse order first the translations and then the rotations are calculated. Forward and Backward Transformations are executed each across the current dynamic Reference System WGS84. Only user defined Reference System Transitions are an exception. They are always calculated directly from the source to the target system. Calculating bidirectional coordinate transformations with Forward and Backward Transformations like in GeoDLL does not lead in minor deviations, that occur in many GIS. With "on" switched flag lForBack the returned text looks dependently of the geodetic source and target Reference Systems e.g. like this: Geodetic Reference Systems: DHDN/PD (DE Old States South ‹±1m), Rauenberg, Bessel to ETRS89 (EU), geocentric, GRS80 Transformation parameters: 7 Parameter Helmert Transformation (Bursa-Wolf) Coordinate Frame Rotation Forward and Backward Transformation separate Forward Transformation source system to WGS84 00597.046300 Translation vector for X-axis [meter] 00071.349100 Translation vector for Y-axis [meter] 00412.187300 Translation vector for Z-axis [meter] -00.89181300 Rotation around the X-axis [seconds] -00.05477000 Rotation around the Y-axis [seconds] 001.54161600 Rotation around the Z-axis [seconds] 0007.5733800 Scale correction factor [ppm] Backward Transformation WGS84 to target system 00000.053700 Translation vector for X-axis [meter] 00000.050900 Translation vector for Y-axis [meter] -0000.087300 Translation vector for Z-axis [meter] -00.00218700 Rotation around the X-axis [seconds] -00.01323000 Rotation around the Y-axis [seconds] 000.02138400 Rotation around the Z-axis [seconds] 0000.0026200 Scale correction factor [ppm] With "off" switched flag lForBack the returned text looks dependently of the geodetic source and target Reference Systems e.g. like this: Geodetic Reference Systems: DHDN/PD (DE Old States South ‹±1m), Rauenberg, Bessel to ETRS89 (EU), geocentric, GRS80 Transformation parameters: 7 Parameter Helmert Transformation (Bursa-Wolf) Coordinate Frame Rotation Forward and Backward Transformation united Transformation source system to target system 00597.100000 Translation vector for X-axis [meter] 00071.400000 Translation vector for Y-axis [meter] 00412.100000 Translation vector for Z-axis [meter] -00.89400000 Rotation around the X-axis [seconds] -00.06800000 Rotation around the Y-axis [seconds] 001.56300000 Rotation around the Z-axis [seconds] 0007.5760000 Scale correction factor [ppm] Unlocking: This function is a component of the unlock requiring function group "parameter determination". 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 no function calls are possible. |