What Coordinate System is Best?

[JustinJohnston]

Hi, 

I am using ESRI Field Maps in association with ArcGIS Online hosted features to collect wetland delineation data.  I am using an iPhone connected to the Trimble DA2 with Catalyst 60.  Was wondering what coordinate system I should be using for the hosted features?  Should it be WGS 1984 Web Mercator Auxiliary Sphere for x,y and WGS 1984 for z?  Should it be WGS 1984 all around?

Cheers,

Justin

[DavidCook2]

WGS84 would be the safest bet as this is the default for the map and requires less reprojecting. 
for z, make sure your feature class is Z-enabled, in the Trimble Mobile Manager App under GNSS settings download the proper Geoid (geoid 18 conus in in continental US) while these values will not `be represented in the FS fields (altitude is always the HAE meters) you can use field calculator or an expression in field maps to call the Z value that DOES get passed from the GPS to the feature. Round(Geometry($feature).z, 2)

i have experimented with many different FS coordinate systems and they all seem to work fine. had a couple concerns and was sweating pretty hard. the biggest mistake i see is that users can keep the position source as integrated and the profile set to what the DA2 needs and this results in a large shift of features.