Selecting a feature class coordinate system when working with Trimble Catalyst

[Alexander_Swain]

Hello, 

I am working to set up ESRI Field Maps with ArcGIS Online hosted features to collect point location data using a Trimble Catalyst DA2 (with paired iOS devices). I don't have much experience setting up this type of workflow and am a bit confused when it comes to selecting the coordinate system for my AGOL hosted features. Is it a better practice to set the CS of the features to match the basemap (e.g., WGS 1984 for the default basemap)? Alternatively, would a better workflow be to set the coordinate system to match the receiver (NAD 1983 2011) or a local coordinate system (e.g., the appropriate NAD 1983 [2011] State Plane system)?

Any guidance here would be appreciated -- hoping to avoid an error at this early stage that will ultimately affect data collection accuracy. 

Thanks, Alex

[ChristopherCounsell · Accepted solution]

Set the layer to web mercator to match the Basemap. The data will project to match the Basemap and be collected to match the Basemap.

Enable GPS metadata capture on your hosted feature later. This should capture data like original coordinates from the GPS.

Set up a location profile on field maps and transformations to wgs84.

What will happen is

• Field maps will use the GPS to capture the data accurately and store the metadata in fields
• A location profile will then be used to transform the data to web mercator to match the map and layer
• You can then use the same transformation path when taking the data offline e.g. project to the local coordinates system in ArcGIS pro.

Consider enforcing gps accuracy / users shouldn't manually reposition points to align to the relatively inaccurate basemap imagery.

This then let's you leverage accurate GPS locations and store data, while also operating in a web gis environment and allowing for future transformations.

If you publish the layer in a different coordinate system to the Basemap you can end up projecting on the fly or mixing transformation paths. Ideally you have everything in the same coordinate system, but otherwise just need to track when and what transformations are occurring.

A transformation can happy between the GPS and the map, and then the map and the layer. Keeping map/layer the same removes this.

[Alexander_Swain]

Thanks Christopher!

Really appreciate the guidance and the extended explanation re: setting the layer CRS to match the basemap. If I understand your guidance correctly, I'll do the following:

• For the feature layer, set the GCS as WGS1984 (WKID 4326) and project to web mercator (WKID 3857).
• The basemap for the Field Maps app will be the ArcGIS default, which shares these respective GCS/PCS definitions.
• Run the Add GPS Metadata Fields geoprocessing tool on the created feature layer.
• Follow standard guidance to create the appropriate Profile (GNSS Coord == NAD83 2011; Map Coord Sys == WGS Web Mercator; select the appropriate datum transformation)
• Enforce GPS accuracy (good recommendation)

One final related question: I have enabled Z Values when creating the feature layer. Is it appropriate in this case to set the vertical spatial reference to WGS84 as well?

In at least one of the tutorials I reviewed, this was left undefined and I haven't yet found definitive guidance on this topic.

Again, thanks for your insight here.