GeoDLL - Geodetic Development Kit
Download of the supported NTv2 / HARN grid files

•  Detailed Description of the current Version
•  Descriptions of the GeoDLL Function Groups
•  User Manual with all Function Descriptions
•  User Manual searching for expressions
•  List of Coordinate and Reference Systems
•  Download of the supported NTv2 / HARN grid files
•  Programming example  Group Prices GeoDLL
•  Download  Place order

Worldwide collection of NTv2 files

In the context of a training measure we have created a worldwide collection of most official NTv2 links.

Click here for the  collection of NTv2 files with the possibility for direct download.

NTv2 grid files in GSB and GSA file format

NTv2 (National Transformation version 2) datum shifts are done with grid files which comes in a binary format (GSB) and an ASCII format (GSA). It can transform coordinates between two different geodetic reference systems. The transformation provides heigh actuality and does not require ellipsoidal heights.

HARN grid files

The Geodetic Development Kit GeoDLL is prepared for coordinate transformations with arbitrary NTv2 grid files and the North American HARN grid files. However, the HARN grid files of the US states are provided as equivalent NTv2 grid files. All by GeoDLL supported NTv2 and HARN grid files can be downloaded from this website.

Support of the NTv2 standard by the Geodetic Development Kit GeoDLL

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.

Depending on the geographic coordinate NTv2 can check several grids contained in the file for the information with the highest accuracy. An NTv2 file always contains a single-precision base grid (parent). Certain areas, such as cities, can be included in the file as local grids with a higher grid density and thus higher accuracy. These local grids overlap areas of the base grid. If a point lies within one of the grids with the higher accuracy, NTv2 will use it, otherwise the point will fall through to the base grid with the lower accuracy.

Quality analysis of GeoDLL and TRANSDATpro with NTv2 test data

The accuracy of NTv2 datum shifts with the program TRANSDATpro and the Geodetic Development Kit GeoDLL from KilletSoft has been investigated twice in detail:

1. Quality analysis by the network operator  Westnetz GmbH.
2. Quality analysis with test data of the  Survey Authorities of Germany.
   Download the  test log.