Hey everyone,
We use ArcGIS Field Maps for lots of things, including construction site inspections. Sometimes we'll walk a feature out (like a stretch of silt fence, for example, or the limits of a revegetated area) to get estimates of materials used to check against what the contractor has reported as used.
We use Web Maps for our Field Maps. I don't know if this is the optimal way to use Field Maps, but it has worked well for us so far. I'll build the map in ArcGIS Pro, share it as a Web Map to ArcGIS Online, and access it through the Field Maps app.
Web Maps are - to my knowledge, at least - constrained exclusively to the WGS 1984 Web Mercator (Auxiliary Sphere) coordinate system. I have been told (from numerous places, including this forum answer: https://community.esri.com/t5/data-management-questions/big-discrepancy-in-acres-calculation/td-p/1038927) that Web Mercator is less than ideal for area or distance measurements: Web Mercator is a "lousy map projection for area calculations" and "should never be used for area or distance calculations."
OK. Fair enough.
But we still need those calculations, and we need them live then and there in the field - in feet or acres, specifically. Web Mercator provides a length and area measurement by default, but it's in meters (and square meters, I'm assuming?), so I've had to add a separate field for calculating lengths and areas in feet and acres.
On top of that, I've been using an Arcade script (that I borrowed and modified from this post: https://www.esri.com/arcgis-blog/products/field-maps/field-mobility/common-calculated-expressions-for-arcgis-field-maps/) to auto-calculate our lengths and areas as the features are collected. But the lengths and areas in the Arcade script are calculating them geodetically, whereas I'm fairly certain the default Web Mercator numbers are planar.
If I want the lengths and areas to match what we'd get if we walked these distances out or manually surveyed these areas, what do I need to do? Would removing "Geodetic" from the Arcade script give me the real-world, walked-out numbers? Or does the fact that these calculations are being done within Web Mercator mean I'll never get the real numbers until I extract the data after-the-fact, project it in our state plane projection, and then manually calculate them? And, again, would I need to use planar or geodetic to get the real numbers in that case, too?
What's the best way to get my field guys the same numbers in Field Maps - in real-time, while they're in the field - that they'd get if they measured these things by hand?
