Is it possible to display GPS coordinates that span two MGA zones on the same map?

06-23-2014 12:24 PM
New Contributor
Hi, I have GDA94 GPS coordinates I collected in Queensland in MGA Zone 56, and a few a little further to the west in MGA Zone 55; however, I haven't found a way to display GPS coordinates from both zones correctly on the same map. The GCS of my template shapefile is GDA94, the units are in decimal degrees (no PCS). I've tried adding my GDA94 GPS XY data to my map and batch transforming the template shapefile and GPS coordinate shapefile to projected coordinate system MGA Zone 56. The result is that all GPS points I collected in MGA zone 56 appear where they should do, but Zone 55 coordinates do not, they appear at the correct latitude, but too far to the East. Is it possible to display GPS coordinates that span two MGA zones on the same map? Also, I have checked my GDA94 GPS coordinates against a Queensland Govt Roads dataset and there are no data collection errors. I'd be grateful for any advice here!
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Esri Notable Contributor
There are a few things you can do. The reason you're seeing the MGA 55 data far to the east, when viewed in MGA 56, is that they have large easting values. That is, they're in the eastern part of MGA 55. When displayed without proper metadata in MGA 56, the large values mean that they still show up to the east of MGA 56. Each MGA zone has the same range of values.

1. Use GDA94 (decimal degrees) for the data. The actual map can still be in MGA 56.
2. Split the MGA 55 data into a separate layer and define it as MGA 55. This will allow ArcMap to reproject it on-the-fly to MGA 56.
3. Reproject the MGA 55 data to MGA 56 permanently.

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