GDA2020 mosaic

[RichardNicholls]

In ArcGIS 10.6 when I load up a mosaic in GDA2020 Zone 50 projection (EPSG:7850) for example, the software comes up with the Spatial Reference as <Undefined> and the XY Coordinate System is Unknown.

Mosaics will display in the correct location if the .mxd is also set to GDA2020 Zone 50, but if set to a Geographic Coordinate System, it's not able to locate the mosaic in the correct place.

What System details are needed in the .ecw for ARC to recognise the imagery as EPSG:7850?

[GordonSumerling]

Hello RIchard,

You are going to need at least ArcMap 10.6.1 and the Coordinate System install as described in the following blog article ArcGIS delivers GDA2020 NTv2 Grid files | Esri Australia Technical Blog Once installed you will be able to use the NTv2 grid files to do the reproject as well.

Also, I would install ArcGIS Pro. The functionality here is far better than ArcMap and you will process the imagery quicker as you have access to more CPU and RAM to do the processing. Ensure you set the parallel processing factor to 95% as JP2's are memory and CPU intensive.

Where possible I would be running ArcMap 10.8.1 or ArcGIS Pro 2.6 to do this work.

Cheers

Gordon