Defining a reference datum

By default, the reference frame for your output positions is in terms of WGS84(G1762) current, and this is automatically encoded with the correct EPSG code (1165). WGS84(G1762) and ITRF2014 positions can be considered the same at the same epoch.

If required, you can define a different target reference datum in the Trimble Mobile Manager app. Any change made to the target reference frame in Trimble Mobile Manager is respected by the Trimble UAV Ground Control app, and includes the correct EPSG code for the chosen reference frame.

To have a consistent coordinate output while using different correction sources, or to use coordinates in a different reference frame from your correction source frame, set the Target reference frame in Trimble Mobile Manager to the required reference frame.

To configure the target reference frame:

  1. Launch Trimble Mobile Manager from the Apps menu of your device.
  2. From the menu, select GNSS Configuration.
  3. Scroll to the GNSS Output section.

  4. Select an option for the Detection mode. The default setting is Select from list and usesWGS84(G1762) current as the GNSS output reference frame. This is equivalent to ITRF2014 current epoch.

    To choose a different target reference datum, select from the options:

    • Auto selection: Trimble Mobile Manager chooses a target reference frame for you based on your location when the session starts.

      If you are unsure of which reference frame to use, choose Auto selection. Trimble Mobile Manager selects a suitable frame for you based on your current location.

    • Select from list: Choose from the list of common datums.

      If the correction source frame you are using is not listed, select Same as source (Transformation off) to forward any positions as received in terms of your correction source reference frame.

    • Same as source (Transformation off): Keeps positions in the same reference frame as positions received from Trimble Corrections Hub or a local correction source.

      If the target reference frame and source reference frame are the same, then no transformation is applied.

    The Geoid field shows the grid file used in Trimble Mobile Manager. The default grid file is EGM96, which is a global geoid.

  5. To choose a different geoid for your output heights, tap Geoid and choose a local grid file from the list. Trimble Mobile Manager downloads the selected grid file and outputs height values in terms of the new grid file.
  6. When you are done making changes, tap the back arrow on the phone to return to the Trimble Mobile Manager Home screen.
  7. Start the Trimble UAV Ground Control app and collect control points. Positions will be in terms of the target reference frame and geoid you selected in Trimble Mobile Manager.

Setting a target reference frame sets the output EPSG code. For more information on EPSG codes and their use, refer to the official website epsg.org/. The EPSG code is undefined when the Same as source (Transformation off) option is selected and the user is connecting to the VRSNow correction source or a local correction source. To record an EPSG code, choose a reference frame from the list that matches your source reference frame. This will be WGS84(G1762) current for VRSNow. For a local correction source, select the same reference frame that is set in the local correction source settings. The EPSG code will be recorded, but no transformation is applied, as the source and target reference frames are the same.