ArcGIS Collector / coordinate system question

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03-31-2023 11:19 AM
ekasboyan
New Contributor

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
MVP Regular Contributor

There can be up to 4 transformations in play:

  • GPS receiver to Web Map (location profile settings in collector)
  • Web Map to Layer (ArcGIS Defaults. Can choose a different default [not custom or non-default gsb]) by publishing the layer with the transformation set at a map properties level.
  • Layer to .gdb, if you are projecting back any downloaded data, or if you are using a referenced (enterprise database) service

The single best thing you can do is to have the same underlying geographic coordinate system across all items i.e. use a custom basemap with the desired spatial reference, and then match the layer and location profile.

The second best thing you can do is ensure that you have the desired transformations set between each phase i.e.

  • Choose a location profile transformation between the GPS provider and basemap. it can be non-defaultgrid-based if you install the grid files on the device
  • Understand the default transformations for your spatial reference and WGS84, and if publishing in a non-WGS84 service, choose a different default transformation as desired when publishing the layer. Choosing a custom or non-default grid service = dropped from the service definition

More information in this (dated) video:

https://www.youtube.com/watch?v=7AuACl8PYKU

Likely better more recent one here (but I have yet to watch it):

https://mediaspace.esri.com/media/t/1_x89iiu6p

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