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Coordinate System for Data Collection

  • 1.  Coordinate System for Data Collection

    Posted 04-03-2024 07:25
    Edited by Anna Peters 04-03-2024 07:26


    I am working with the Trimble DA2 and Esri Field Maps. When I create my data in ArcGIS Pro and upload it to ArcGIS Online, should the hosted feature service coordinate system should match whatever the GNSS output coordinate system is, for example, NAD 1983 (2011) with RTX? Then if a transormation is needed between that data and the basemap I use, that is completed through the location profile? Thanks!

  • 2.  RE: Coordinate System for Data Collection

    Posted 04-03-2024 10:27

    I am working on the 4th edition of my textbook The Global Positioning System and ArcGIS. It is used in GIS courses to provide a platform for students to collect data with Trimble equipment and software (Connect and TerraFlex) and then the install said data into ESRI software (ArcGIS Pro, ArcGIS Online, etc.). For the Third Edition please see: 



    I've not yet revised the critical importance of matching GPS data with existing GIS data (datum, coordinate system, scale, etc.) but I know enough at this point make a suggestion regarding Field Maps and its use with other established coordinate systems (e.g., WGS84 UTM): BEWARE! Field Maps uses a map projection that is used for "Web mapping applications". 


    Web MercatorGoogle Web MercatorSpherical MercatorWGS 84 Web Mercator[1] or WGS 84/Pseudo-Mercator is a variant of the Mercator map projection and is the de facto standard for Web mapping applications. It rose to prominence when Google Maps adopted it in 2005. It is used by virtually all major online map providers, including Google Maps, CARTOMapbox,[3] Bing MapsOpenStreetMapMapquestEsri, and many others.[4] Its official EPSG identifier is EPSG:3857, although others have been used historically. 

    Web Mercator is a slight variant of the Mercator projection, one used primarily in Web-based mapping programs. It uses the same formulas as the standard Mercator as used for small-scale maps. However, the Web Mercator uses the spherical formulas at all scales whereas large-scale Mercator maps normally use the ellipsoidal form of the projection.[citation needed] The discrepancy is imperceptible at the global scale but causes maps of local areas to deviate slightly from true ellipsoidal Mercator maps at the same scale. This deviation becomes more pronounced further from the equator, and can reach as much as 40 km on the ground. 

    While the Web Mercator's formulas are for the spherical form of the Mercator, geographical coordinates are required to be in the WGS 84 ellipsoidal datum. This discrepancy causes the projection to be slightly non-conformal. General lack of understanding that the Web Mercator differs from standard Mercator usage has caused considerable confusion and misuse. For all these reasons, the United States Department of Defense through the National Geospatial-Intelligence Agency has declared this map projection to be unacceptable for any official use.

    -- Michael Kennedy

  • 3.  RE: Coordinate System for Data Collection

    Posted 04-03-2024 18:32

    Hi Anna,

    Take a look at this blog published last year on exactly this topic, hopefully it helps!

    Best regards,


    Mark Kellaway

  • 4.  RE: Coordinate System for Data Collection

    Posted 04-04-2024 08:59
    Edited by Anna Peters 04-04-2024 08:59

    Hi Mark,

    Thanks for sharing. I read through and it is a helpful article, except doesn't quite answer my question. It talks about the coordinate system of the basemap and web map but not of the hosted feature service data being added into the web map. I think I found the answer in the blog post below. The data should be in the same geographic coordinate system as the GNSS coordinate system. This can be done in conjunction with the Esri basemapping or to create custom basemaps in the same geographic coordinate system as the GNSS corrections. 

    High-accuracy mobile data collection in NAD83 CSRS

    Esri remove preview
    High-accuracy mobile data collection in NAD83 CSRS
    Tips & tricks for setting up ArcGIS Field Maps for collecting data in NAD83 CSRS when in the field.
    View this on Esri >

    Anna Peters

  • 5.  RE: Coordinate System for Data Collection

    Posted 04-04-2024 12:15
    Edited by Joel Cusick 04-04-2024 12:22


    You are correct with the Trimble blog post.   It is not entirely clear on the location profile screenshot in the post why you would use this: see below.   In one, and only one workflow would this make sense, and ONLY in Field Maps that, in the case of using TMM, you keep MOCK location OFF on android.  In this case, with incoming GNSS stream based on NAD83(2011), with NAD83(2011) with hosted feature layers in NAD83 (2011) and a ESRI basemap (PCS - Web Mercator) will this work.  YOU DO NOT HAVE TO transform a basemap to match the incoming datum of the augmentation, in FIELD MAPS.   The only way to know Anna is to occupy survey control (a modern OPUS share would be ideal).   The sheer number of datum hoops will drive you nuts.    I'm emphasizing Field Maps in this post, because currently in QuickCapture and Survey 123, where you have to activate MOCK location in TMM, you cannot hit NAD83(2011) survey control with a, say, NTRIP augmentation fed into either software based on NAD83(2011).  Its kinda nuts that this is occurring across the FM vs QC/Survey123 mobile platforms, but that is the case.  Love to have someone prove me wrong.   I'm about to contact the team at ESRI.  Its not an issue with TMM, but QuickCapture and Survey123.

    Joel Cusick

  • 6.  RE: Coordinate System for Data Collection

    Posted 04-10-2024 10:14

    I did some more testing.

    Set up #1:

    Using the custom basemap in the local county coordinate system, then publishing the hosted feature service in that same local county coordinate system. The GNSS input is always NAD 1983 (2011).

    Transformation is NAD_1983_HARN_To_NAD_1983_2011 in Esri Field Maps.


    Set up #2:

    Data, custom basemap, and GNSS output is all in NAD 1983 (2011).

    No transformation is occurring in field maps, but then post-processing of the data occurs by projecting the data to the local county coordinate system in ArcGIS Pro.


    I tested on two devices with varying accuracy levels. One was an Eos Arrow Gold CM Receiver. I actually ended up having more accurate results with the Set Up #1 with the hosted feature service being in the local county coordinate system than it being in NAD 1983 (2011) for Z values. X and Y were pretty comparable. With this data in the local county coordinate system already, it seems to make more sense to stick with set up #1 since I do not need to post-process. 

    Anna Peters