GNSS (GPS) Spatial Reference Systems

11 Apr 2023

Note: This information is provided as a general reference and does not imply that Juniper Systems provides full support or formal definitions for any specific spatial reference system, datum, coordinate system, projection, or other references. For formal definitions of spatial reference systems, consult the governing authority.

GNSS (GPS) receivers, such as the Juniper Systems Geode and the u-Blox NEO M8 series (integrated into our Mesa 3 Windows and other rugged handheld computers), output messages in NMEA 4 format. When using these receivers with SBAS such as WAAS, or with Atlas L-band corrections, the receivers provide data based on the ITRF 2014 (Current Epoch) spatial reference system. For more technical details, see ublox Geodetic Coordinate Systems and Ellipsoids. In most GIS and other mapping data collection apps, the default selection for GPS receivers is World Geodetic System 1984 (WGS84) which is for the most part equivalent.

If you are using NTRIP corrections such as for RTK within the United States (for example, with the Juniper Systems Geode), the spatial reference system will typically be equivalent to North American Datum 1983 (2011), though not guaranteed. Research on each mount point is required.

For information on how to apply a coordinate transformation such as in Uinta or with ESRI ArcGIS Field Maps, see

Errors can occur when data (or other geo-referenced layers, such as background imagery) are loaded using different spatial reference or coordinate reference systems. For more information, see Geode appears to be inaccurate in good conditions, Accuracy of background imagery in mapping apps, and Spatial Reference Systems.

For assistance creating GNSS/GPS coordinate transformations after the data has been collected, Juniper Systems recommends the following partners:

Note: You can use the following tool to set up coordinate transformations after data collection, but the procedure is technical. 

https://geodesy.noaa.gov/TOOLS/Htdp/Htdp.shtml

The Geode receiver uses a custom compressed model to approximate geoid offset heights to calculate an orthometric height or mean sea level (MSL) such as for determining elevation or altitude. The receiver board in the Geode provides a MSL value calculation that is based on the EGM96 ellipsoid model. An app, such as Juniper Systems Uinta (version 1.7.0 and later), can be used to apply a known geoid model for recording an orthometric height value based on ellipsoidal height data from the Geode. According to ESRI, most GIS data collection apps use a global positioning system (GPS) unit to report heights relative to the World Geodetic System of 1984 (WGS84) ellipsoid. (See https://pro.arcgis.com/en/pro-app/latest/help/mapping/properties/vertical-datums.htm.)

Reviewed and approved: JF, 11Apr2023