Coordinate system

Trimble Access provides a comprehensive database of coordinate systems used around the world. The database is continually updated to reflect changes to different zones. To customize the list of coordinate systems available, see To customize the coordinate system database.

To select the coordinate system settings for the job from the coordinate system database:

  1. Tap and select Job. The current job is already selected.
  2. Tap Properties.
  3. Tap Coord sys.
  4. In the Select coordinate system screen, select Select from library. Tap Next.
  5. From the lists, select the required System and Zone.

    Drag your finger up the list to scroll, or press the first letter of the country name on the keypad to jump to that section of the list.

    When you have selected the System and Zone, the following read-only fields are updated:

    • Local datum: The local datum for the selected coordinate system and zone.
    • Global reference datum: The datum of RTK measurements, such as the reference frame of base stations including VRS.
    • Global reference epoch: The epoch of realization of the Global reference datum.
    • Displacement model: The displacement model used to propagate RTX coordinates between ITRF 2020 at the epoch of measurement and the global reference frame.

    If you perform an RTK survey in the job, you must make sure the selected real-time correction source is providing GNSS positions in the same datum as that specified in the Global reference datum field.

  6. If the job will contain GNSS observations and you want to use a geoid model or datum grid file, you must have copied these files to the controller.
    1. To select a geoid model, enable the Use geoid model switch. Select the file in the Geoid model field.
    2. To select a datum grid file, enable the Use datum grid switch. Select the file in the Datum grid field.

      The semi‑major axis and flattening values for the selected datum grid file are displayed. These details overwrite any already provided by a specified projection.

  7. Select the type of Coordinates to use. The default is grid. To use ground coordinates, see To set up a ground coordinate system.
  8. Enter the Project height. See Project height.
  9. Tap Store.

Alternatively, you can define the coordinate system using one of the methods below.

Do not change the coordinate system or calibration after you have staked out points, or computed offset or intersection points. If you do, the previously staked out or computed points will be inconsistent with the new coordinate system and any points computed or staked out after the change.