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ArcGIS Collector / coordinate system question

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06-01-2023 01:56 PM
darry04
by
New Contributor
‎06-01-2023 01:56 PM

Hi,

I collected some points using the Collector app, using an RTK correction system to provide cm level accuracy. The point layer I was using for was in NAD 83 CSRS UTM Zone 20N. In the Collector app, the GNSS Coordinate System used was WGS 1984, Map Coordinate System was WGS 1984 Web Mercator Auxiliary Sphere.

So it seems my points were collected in WGS1984. For some reason I was under the impression there would be a transformation taking place considering the layer the points were being added to was in NAD 83 " ". When I try to project them back into NAD83 "" they aren't on my map. Is there a way to successfully project these coordinates into NAD83 CSRS UTM Zone 20N from WGS84? Ultimately the projection on the fly provided by AGOL / ArcMap represent the points properly in WGS84 laid over a satellite image that is in NAD 83 CSRS UTM Zone 20N, but would prefer to have all layers in my .gdb in the same coordinate system of course...

Any advice?

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1 Reply
ChristopherCounsell
by MVP Regular Contributor
MVP Regular Contributor
‎06-01-2023 04:21 PM

A coordinate system is at play at:

  • The GPS
  • The Web Map (set by the basemap)
  • The service (set at publish)
  • (sometimes) the source data, when working with referenced ArcGIS Server services

There are up to 3 transformations that can occur:

  • DT1: GPS Receiver to Web Map (using location location profiles on device)
  • DT2: Web Map to Layer (using default or service defined datumTransformation)
  • DT3: Layer to geodatabase (for ArcGIS Server services where the source data is different to the services coordinate system)

https://youtu.be/7AuACl8PYKU?t=772

You should:

  •  Try have the same coordinate system across the board, to make life easier
  • Ensure that the desired datum transformation occurs at each stage and are supported
  • Be aware of the behaviour of DT2
  • Be aware of the behaviour of when publishing a service i.e. does it reproject on publish, do custom datumTransformations get created etc

So for you you ideally want:

  • NAD83 CSRS UTM Zone 20N GPS
  • NAD83 CSRS UTM Zone 20N  basemap in map
  • NAD83 CSRS UTM Zone 20N service

Or if oyu don't have a custom basemap service:

  • NAD83 CSRS UTM Zone 20N GPS + location profile to datumTransformation to WGS84
  • WGS 84 basemap
  • NAD83 CSRS UTM Zone 20N service, with no (default) or chosen datumTransformation at a service level.

For DT2 How can I control how hosted feature layers are reprojected when viewed on ArcGIS Online basemaps?

https://doc.arcgis.com/en/arcgis-online/reference/faq.htm#anchor69

Also, ArcGIS Collector is retired. You should be on ArcGIS Field Maps.