NTv2 means National Transformation Version 2 and describes an in Canada developed method for the transformation of georeferenced data from one reference system to another.
An NTv2 file contains the differences between the two reference systems in a grid.
This allows converting coordinates of the source system to the target system with high accuracy.
The surveying authorities of many countries have developed a large number of NTv2 grid files and made them available mostly free of charge, sometimes for a fee. The NTv2 files can usually be downloaded from the web sites of the respective surveying authorities. However, it is often difficult to find the appropriate web pages with the appropriate download links. The fact that the information on the pages is written in the respective national language makes the research a challenge. Some countries release their NTv2 solutions only after registration or after some administrative effort.
In the context of a training measure the company Killet GeoSoftware Ing.-GbR, briefly KilletSoft, has let create a worldwide collection of most official NTv2 links. On the web page https://www.killetsoft.de/t_ntv2_e.htm the NTv2 solutions are listed according to continents and countries.
NTv2 files freely provided by the originators can be downloaded there directly. In addition, links to the original web pages of the originator are provided, where mostly the latest versions of the NTv2 files can be found. If a registration is required for the use of an NTv2 file or if the originator charges a usage fee, the registration address and further information are provided in an info file.
For some ordinarily chargeable NTv2 files the permission for free use with software developed by KilletSoft has been negotiated with the originators. Therefore these Ntv2 files are encrypted and work only with the Geodetic Development Kit GeoDLL and with the programs TRANSDATpro for Coordinate Transformations, NTv2Poly and NTv2Tools. Detailed information about the software can be found on the website of KilletSoft.
The worldwide collection of NTv2 files is unique in this completeness. Informations about freely available NTv2 files still missing in this collection are welcome anytime.