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Can I convert GPS coordinates from decimal degrees to New Zealand Transverse Mercator in Didger?

Yes. In Didger 5, the New Zealand Transverse Mercator projection can be found by using the Map | Change Projection command. When the Assign Coordinate System dialog opens, the system can be found under Predefined | Projected Systems | Regional/National | New Zealand.

I
n Didger 4, it is possible with a few modifications. Didger 4 does not support the New Zealand Transverse Mercator projection directly, but you can simulate this projection using the regular Transverse Mercator projection and entering specific projection parameters. For Transverse Mercator, these are: False Easting, False Northing, Scale, Central Scale Factor, Central Latitude and Central Longitude. If you know this information you can simulate the NZTM projection.

This site lists this information:
http://www.linz.govt.nz/data/geodetic-system/datums-projections-and-heights/projections/new-zealand-transverse-mercator-2000.

The only potential problem is the datum. The above link states that the NZTM uses the NZGD2000 datum. We do not offer any datums specific to New Zealand, but we do offer the ability to create your own datum. However, the above site also states that:

"NZGD2000 is essentially coincident with the World Geodetic System 1984 (WGS84). This is the reference system that is used by GPS receivers. It means that for most practical purposes WGS84 coordinates can be assumed to be the same as NZGD2000 coordinates, hence no transformation is necessary."

If WGS84 is sufficient for your needs, the exact steps to convert a data, vector or raster file are:

  1. Go to File | Import, select your data, vector or raster file and click Open.
    1. If you are importing a vector file (ie. SHP, DXF, or MIF), in the Define Import Options dialog box, select Projected Coordinates, Category=World/Continental Projections, System=Unprojected Lat/Long, and Datum=World Geodetic System 1984. Select any other properties you wish (ie. Line, Fill or Symbol Properties) and click OK.
    2. If you are importing a data file (ie. XLS, TXT, or DAT), in the Import Data File dialog box, select the appropriate data import options and click Import. In the Define Import Options dialog box, select Projected Coordinates, Category=World/Continental Projections, System=Unprojected Lat/Long, and Datum=World Geodetic System 1984. Select any other properties you wish (ie. Symbol Properties) and click OK.
    3. If you are importing an uncalibrated raster file (ie. TIF, JPG, GIF), the Image Registration and Warping dialog will appear. Calibrate the image using three or more known points on the Calibration Points tab. Then go to the Options tab, select the Specify radio button, and click the Coordinate System button. Select Projected Coordinates, Category=World/Continental Projections, System=Unprojected Lat/Long, and Datum=World Geodetic System 1984. Click OK. Click OK.
  2. Once the data or image is imported, go to View | Change Projection.Change the System to Transverse Mercator.Click on the Projection Settings button and enter the settings specified in the link above. Keep World Geodetic System 1984 as your datum and click OK.
  3. The projection is converted. You can now export the data to a new file or import additional files.

Updated: September 28, 2016

 

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