Offline GNSS corrections

Offline GNSS corrections are the application of differential corrections to autonomous GNSS positions after they are collected.

When you enable offline GNSS corrections in the map workspace, features are automatically processed within 24 hours of being synchronized to the map workspace. You can see what base stations are available to be used during processing here.

To be able to enable offline GNSS corrections, you must be a project administrator. To collect features that will be processed using offline GNSS corrections, field users must be using a TerraFlex Premium license when collecting data in the field.

To enable the application of offline GNSS corrections to new and updated features collected using a TerraFlex Premium license in the current workspace:

  1. As the project administrator, click and then click Positioning.

  2. Select the Offline GNSS tab.

  3. Click the Offline GNSS corrections toggle switch to change it to the enabled position.

To prevent TerraFlex field app users from being able to collect a feature unless the offline GNSS corrected accuracy does not meet a specified accuracy threshold, in your form template select the Enable Accuracy Based Logging check box and enter the required accuracy value. For more information, see Editing template properties.

Offline GNSS corrections enabled in a Map Viewer workspace are automatically enabled when creating a .tfproj file from the same workspace. Alternatively, GNSS corrections can be enabled from within Terra Office when creating a .tfproj file. TFOUT files from TerraFlex Local projects can then be loaded back into Terra Office for post-processing.

When Offline GNSS corrections is enabled in the workspace, features can be collected for processing using offline GNSS corrections in TerraFlex as long as:

  • The field user signed in to TerraFlex has a TerraFlex Premium license.

  • The project has been synchronized to TerraFlex to pick up the change to the Offline GNSS corrections setting.

  • The TerraFlex software is connected to a GNSS receiver that supports offline GNSS corrections. These receivers are:

    • Trimble R580 GNSS system

    • Trimble Catalyst DA2 GNSS receiver

    • Trimble R12 GNSS receiver

    • Trimble R2 GNSS receiver

    • Trimble R1 GNSS receiver

    • Trimble handheld devices with integrated GNSS
      • Trimble TD650 GNSS handheld
      • Trimble TDC150 handheld
      • Trimble Empower EM100 module (on supported Trimble Android and Windows devices)

Features are collected as usual using TerraFlex. In addition:

  • For every static vertex on a feature, 10 positions are logged for offline GNSS corrections.

  • If the project is using offline GNSS corrections as the primary correction source, the TerraFlex field user can set the Primary Display Value field to After offline GNSS processing so that they can see the expected accuracy of the data being captured. See Data collection settings.

Features are automatically processed using offline GNSS corrections within 24 hours of being synchronized to the map workspace. The status of processed features is indicated in the Activity log and in the feature selection panel.

To view the Activity log, click at the top right of the map workspace. For more information, see Viewing recent activity.

Features can be collected for an unlimited time in TerraFlex before being synchronized to the map workspace and processed. However, Trimble recommends synchronizing data to the cloud regularly.

Accuracy results for features that have been processed using offline GNSS corrections can be viewed per feature or per group of features using the Accuracy panel.

For more information, see Reviewing features.