At present 2 to 7 cm per year
GeoDLL supports the development of geodetic software by providing geodetic functions, which are put together into function groups for specific tasks. To use highly accurate coordinate transformations with NTv2 grid files in own developments a license for the additional function group "NTv2 Grid Data" can be purchased. Requirement for the use of this function group is a license of the function group "Coordinate Transformations".
NTv2 means "National Transformation Version 2". The NTv2 method uses binary files to perform accurate datum shifts from one geodetic Reference System to an other. An NTv2 file contains the differences between the two Reference Systems as geographic seconds in a grid. A bilinear interpolation is used to calculate the exact coordinates for a point in the target Reference System.
NTv2 is designed to check multiple grids for the most accurate shift information. An NTv2 file contains a low density base grid (parent). Certain areas such as cities can have high density local sub grids. The sub grids overlay portions of the base grid. If a point is within one of the high density sub grids, NTv2 will use the high density grid, otherwise, the point falls through to the low density grid.
A description of the NTv2 algorithm can be found in the following sources:
The NTv2 grid files supported by the program TRANSDAT and the function librariy GeoDLL you can download here from the KilletSoft website!
The program TRANSDAT and the function librariy GeoDLL supports NTv2 standard Coordinate Transformations with high accuracy. Amongst others the NTv2 gridfile BeTA2007 can be used for transformations within Germany with results in sub-meter accuracy. The gridfile is provided by the "Arbeitsgemeinschaft der Vermessungsverwaltungen der Länder der Bundesrepublik Deutschland" (ADV), along with a documentation and a set of test data. The test data contain 31 spaced points on the territory of the Federal Republic of Germany in different variations with coordinates in both Reference Systems DHDN90 and ETRS89.
Comparative calculations with the test data of the ADV, done by the engineering office Killet Software Ing.-GbR, attest to the software TRANSDAT and GeoDLL a very good self-consistency. Here are the results:
You can download the test protocol and the tables with the corresponding calculations from our server.
Detailed descriptions of all geodetic functions of this function group you find here in the online manual!
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GeoDLL / TRANSDAT
WINDOWS© 10 compatible
TRANSDAT / GeoDLL