An NTv2 transformation would commonly be performed in ArcGIS Desktop in the following circumstances:

• User wishes to create a duplicate feature class that is on GDA94, where the source was on either datum AGD66 or AGD84. This would be performed in ArcCatalog, using the Project tool.
• User wishes to transform the coordinate system of an ArcMap dataframe from either AGD84 to GDA94 or from AGD66 to GDA94. This would be performed in ArcMap.

The procedure to undertake each of the above is provided below.

Steps required to create a duplicate feature class that is on GDA94, where the source was on either AGD66 or AGD84, using the NTv2 transformation method :

1.  From within ArcCatalog, start ArcToolbox.
2.  Initiate the Project tool (from beneath ArcToolbox> Data Management Tools> Projections and Transformations). The form displayed in Figure 1, below, will be  displayed.
3. Drag the feature class that is to be duplicated into the Input Dataset or Feature Class text entry box. Providing that the subject feature class has a coordinate system defined, the Input Coordinate System (optional) text entry box will be populated. In this example our input feature class is in Australian Map Grid, Zone 55, on AGD66.
4. Enter a name for the Output Dataset or Feature Class in the supplied text entry box.
5. Select the required Output Coordinate system. Transforming to GDA94, requires that GDA_1994_MGA_Zone 55 be selected. (Since the original data is in AMG Zone 55, MGA Zone 55 must be chosen as the corresponding map grid zone for GDA94).
6. Under Geographic Transformations (optional), the AGD_1966_To_GDA_1994_11_NTv2  must be chosen from the drop down box. This option will utilise the A66_National_13_09_01.gsb file, and hence transform the data?s datum from AGD66 to GDA 1994.  It could be applied to any Australian dataset that exists on AGD66. Other displayed geographic transformation options relate to alternative transformation methods. They are described under the ArcGIS Desktop Australian Datum Transformation Options.  If a user was transforming from AGD84 to GDA 94, the AGD_1984_To_GDA_1994_5_NTv2 option would need to be selected . Again, it could be applied to any Australian dataset that exists on AGD84, that a user wishes to translate to GDA94. This option will utilise the National_84_02_07_01.gsb file to transform from AGD84 to GDA 1994.
7. Click OK and the new feature class will be created in the transformed datum.

Steps required to  transform the coordinate system of an ArcMap dataframe from either AGD84 to GDA94 or, from AGD66 to GDA94, using the NTv2 transformation method:

1. In ArcMap, for a subject dataframe, select the Properties context menu, by right clicking the dataframe listing.  For this example the ArcMap dataframe is in AMG Zone 55, on AGD66 and we are transforming the dataframe?s datum from AGD66 to GDA94.
2. In the form that appears, select the Coordinate System Tab, then click the Transformations button.  The Geographic Coordinate System Transformations form then appears.  We are converting from AGD66 to GDA94, hence the GCS_Australia_1966 coordinate system will be displayed under ?Convert from
3. Under Into: select Australia and New Zealand\Geocentric Datum of Australia 1994.
4. From the Using :  drop down list, AGD_1966_To_GDA_1994_11_NTv2  must be chosen. (Note that this option is only available when the subject dataframe is on AGD66; it will utilise the A66_National_13_09_01.gsb file to perform the transformation).  If the subject dataframe was on AGD84, GCS_Australia_1984 would be listed beneath Convert From:. Translating to GDA94 would then require Australia and New Zealand\Geocentric Datum of Australia 1994 to be selected from the Into: drop down list, and  the AGD_1984_To_GDA_1994_5_NTv2 option would need to be selected, from the Using :  drop down list. (In this case, the National_84_02_07_01.gsb would be used by ArcGIS to perform the transformation from AGD84 to GDA).  Refer to ArcGIS Desktop Australian Datum Transformation Options for information about the alternatively listed transformation methods.
5. Click OK  to close each open form and the coordinates of the dataframe will be transformed.

ArcGIS Desktop Australian Datum Transformation Options

Click here to view the Australian Datum Transformation options available for ArcGIS Desktop.

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