Prototype and description of the function getelevation33() (Function of the unlock requiring group "Elevation calculations") |

getelevation33() Elevation from the 3 / 30 sec. elevation model CGIAR / GLOBE for a point. Prototype of the DLL function in C++ syntax (attend lower case!): extern "C" __declspec(dllimport) unsigned long __stdcall getelevation33( double nGeoLon, double nGeoLat, unsigned long lInterpol, short *nElevation); Prototype of the DLL function in Visual Objects syntax: _DLL function getelevation33(; nGeoLon AS REAL8,; // 8 Byte nGeoLat AS REAL8,; // 8 Byte lInterpol AS LOGIC,; // 4 Byte nElevation REF SHORTINT); // 4 Byte as logic pascal:geodll32.getelevation33 // 4 Byte The function tries to determine the ground level elevation at a point defined by geographical coordinates from the 3 seconds elevation model (90 m raster) CGIAR. If it fails, e.g. due to missing data, the ground level elevation is determined from the 30 seconds elevation model (1 km raster) GLOBE. The 30 seconds elevation model of the NASA Shuttle Radar Topographic Mission "Global Land One-Kilometer Base Elevation (GLOBE)" as data set G.O.O.D. is free available for private and commercial purposes. The 3 seconds elevation model "SRTM 90m Digital Elevation Data" is free available for non commercial purposes and can be acquired for commercial use economically priced from the CGIAR. With a license for the GeoDLL function group "Elevation calculations" you only acquired the right to use the functions to compute the elevation data. The elevation data are subject to the copyright of the "GLOBE Task Team" and the "CGIAR Consortium for Spatial Information". This organizations revised and supplemented the original data of the NASA. Please consider their terms of use and their copyright conditions. Detailed descriptions of the elevation models and information for free downloading of the elevation data from the Internet you find in the documentation of the following functions: CGIAR: Function getelevation03() GLOBE: Function getelevation30() Differences between the elevation models GLOBE and CGIAR: Elevation model: GLOBE CGIAR GeoDLL function getelevation30() getelevation03() Range longitude [degrees] -180 to 180 -180 to 180 Range latitude [degrees] -90 to 90 -60 to 60 Resolution [sec] 30 x 30 3 x 3 Resolution [m] 925 x ‹= 925 90 x ‹= 90 Horizontal reference WGS84 WGS84 Vertical reference Mean Sea Level Mean Sea Level Horizontal deviation [m] ‹ 6 ‹ 6 Vertical deviation [m] ‹ 10 ‹ 7 Number of files 16 1728 File size [MB] 101/126 70 Range per file [degrees] 90 x 40/50 5 x 5 The parameters are passed and/or returned as follows: nGeoLon Geographic longitude of the point to get the ground elevation from in [degrees] notation vggg.ggg in the Reference System WGS84. nGeoLat Geographic latitude of the point to get the ground elevation from in [degrees] notation vgg.ggg in the Reference System WGS84. lInterPol TRUE: The ground elevation is interpolated from the 4 corner points of the raster field containing the coordinate. The computation is exact, but relative slow. FALSE: The ground elevation corresponds to the value of the raster field containing the coordinate. The computation is less exact, but relative fast. nElevation Ground elevation over the Mean Sea Level in meters as result of (ref) the computation. In the presence of a water cover the value 0 is returned. If an error occurs the function returns the value 9999. 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 "Elevation 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. |