Pitney Bowes MapXtreme User Manual
Page 588
Appendix H: Elements of a Coordinate System
National Transformation v. 2 (NTv2)
MapXtreme v7.1
595
Developer Guide
The New Zealand grid shift file converts from the NZGD49 datum to the NZGD2000 datum.
Detailed information and an online converter can be found at the Land Information New Zealand
(LINZ) web site:
Germany
The following grid shift file is included for Germany:
BETA2007.gsb–used for conversion from DHDN datum to ETRS89
For more information and to download the official grid shift file, see the Information and Service
System for European Coordinate Reference Systems (CRS EU) web site:
Configuration File
The NTv2 configuration file (NTv2.xml) is an XML file that you can edit to add new grid shift files for
other datum conversions and turn NTv2 on or off for particular grid shift files.
To add new grid shift files, you must specify three parameters:
•
grid shift file name
•
source datum
•
destination datum
You can define a datum in various ways. For example, when both the source and destination datums
are defined in MapXtreme, the datums are defined in the configuration file by the numbers assigned
to them in the MapXtremeCoordinateSystemSet.xml file. In this example for New Zealand, the XML
in the configuration file will look like this (application of bold text is for emphasis only):
- <NTv2Conversion>
<Description>NTv2 Conversion for New Zealand</Description>
<GridFile>NZGD2KGRID0005.GSB</GridFile>
<Enabled>true</Enabled>
- <SourceDatum>
<DatumID>1010</DatumID>
</SourceDatum>
- <DestinationDatum>
<DatumID>117</DatumID>
</DestinationDatum>
</NTv2Conversion>
- <NTv2Conversion>
Sometimes, however, datums are not that easily defined. You may need to supply datum shift values
(and sometimes even ranges for them) in order to define a datum. For example, the sample XML
below shows the definition of the NAD 27 datum for Canada. Here, the ellipsoid, shift values for
x,y,z, and their ranges have been used to define the datum (bold text is for emphasis only):
- <NTv2Conversion>
<Description>NAD 1927 to NAD 1983 conversion for Canada</Description>
<GridFile>NTV2_0.GSB</GridFile>