topic Re: GNSS Horizontal Accuracy in ArcGIS Field Maps Questions

GNSS Horizontal Accuracy

becyr — Tue, 07 Oct 2025 20:57:25 GMT

HI All,

I tested two different sets of Field Maps at a Geodetic Station:

Map 1

Feature Dataset Coordinate System: WGS 1984 Web Mercator Auxiliary Sphere
Basemap Coordinate System: WGS 1984 Web Mercator Auxiliary Sphere

Map 2

Feature Dataset Coordinate System: NAD 1983 HARN Adj.... (US Feet)
Basemap Coordinate System: WGS 1984 Web Mercator Auxiliary Sphere

For both maps, I used a location profile set to WGS_1984_(ITRF08)_To_NAD_1983_2011. And the NTRIP Setting set to Local Network, Mount Point: RTXM_34_NAD83(2011), Geoid: GEOID18(Conus). When collecting points at the Geodetic Station, both maps recorded locations approximately 1.5 meters off from the geodetic station. When collecting points without a location profile, although Field Maps generated a location profile warning, the collected points were in much closer proximity to the actual station location. Any suggestion on what I am doing wrong.

Keep in mind the Mobile Manager Status & Point Coordinates without a Location Profile where the same and they were in the same proximity of the station. 😕 should I let my field worker collect data in this unrecommended practice? Feels wrong

Oh, my device is Trimble R2. 5.48 Firmware ...I guess I can't update the firmware since our warranty is expired

Re: GNSS Horizontal Accuracy

Y_Chau — Wed, 08 Oct 2025 04:44:08 GMT

Since you use WMAS basemap in both scenarios the GNSS should be transformed to WMAS. Your location profile will now depend on the coordinate system of the GNSS corrections. So, find out exactly what this mount point is serving. I am guessing that the GNSS corrections are already transformed that is why the measurements are correct without location profile.

Re: GNSS Horizontal Accuracy

becyr — Wed, 08 Oct 2025 13:59:13 GMT

Thanks @Y_Chau what will be the best way to find out what the GNSS is outputting. The output reference frame is NAD83(2011) (EPOCH:2010);

Preview

Re: GNSS Horizontal Accuracy

jmaxwell_braun — Wed, 08 Oct 2025 15:50:20 GMT

@becyr Does the transformation you mentioned have a "~" in front of it? That indicates it's going in reverse, from NAD 1983 2011 to WGS 84. Without that, it's transforming from WGS 84 to NAD 83 2011. It should be "~WGS_1984_(ITRF08)_To_NAD_1983_2011".

In Field Maps location profile, GNSS Coordinate System should be set to "GCS NAD 1983 2011" (code 6318). Map coordinate system set to "WGS 1984 Web Mercator Auxilliary Sphere" (code 3857).

If the output reference frame in Mobile Manager is set to NAD83(2011) EPOCH 2010, this setup should work.

Re: GNSS Horizontal Accuracy

becyr — Wed, 08 Oct 2025 19:32:12 GMT

@Y_Chau Yes, I have the Datum Transformation set as that. I have tired deleting both applications and starting fresh. I have tried setting the location profile zoom level to the county level & greater extent. But nothing works🤔 . My position status is RTKFixed and Geoid18(Conus) Played around with CMRx, RTCM, CRM_Plus

Re: GNSS Horizontal Accuracy

Debert — Mon, 13 Oct 2025 18:44:57 GMT

Depending if you've updated to the new version of Field Maps 25.2 or not, you may have to reconfigure your receiver. I've posted the new workflow link here New TMM x FM Connection Workflow