Antenna height handling in Trimble Positions

The new version of Trimble Positions includes the following improvements in handling antenna information:

  1. It is possible to specify antenna height when collecting GIS features with Positions Mobile extension for ArcGIS for Windows Mobile. Antenna height is a vertical distance between an antenna and a feature that is collected and will be applied when the GIS feature geometry is collected. For example, if a pole-mounted antenna is used to collect manholes, the length of a pole can be specified as an antenna height. That will enable calculation of precise heights for actual features (manholes). Antenna height will be stored into session data for each logged GNSS position.
  2. It is possible to select a proper antenna type when collecting GIS features with Positions Mobile extension for ArcGIS for Windows Mobile. A selected antenna type and a measurement method will be used to correct antenna height entered by a user to match the actual distance between the antenna’s phase center (the position which is calculated by the GNSS receiver) and GIS feature. Antenna type will be stored in a GNSS session (if created).
  3. The Positions Desktop add-in will use antenna height and type information collected by the Positions Mobile extension and the Positions ArcPad extension if/when feature geometry is recalculated, for example after session correction. Antenna height information will be displayed for each GNSS position logged and antenna type will be shown when session features are displayed in the Positions Desktop add-in dockable window.

In the GNSS Settings page in the Positions Mobile extension there is a new “Antenna” group item which displays currently set antenna height and type.

Positions Mobile extension - GNSS Settings

By clicking on this group it is possible to set antenna height as distance in meters and to select the default antenna type. When selecting antenna type, the selection will depend on the receiver type currently connected or the one last used. If there is more than one potential measurement method for a selected antenna type, the user will be required to select the one that matches his/her needs.

Positions Mobile extension - Set Antenna Positions Mobile extension - Select Antenna Type

It should be noted that the software cannot detect if a wrong antenna type is selected by the user. GNSS receivers may provide information if an external or an internal antenna is connected and that information will be displayed in the GNSS Status page.

Positions Mobile extension - GNSS Status

If a selected antenna type does not match the information coming from a receiver, the Positions Mobile extension will try to use a proper antenna type. For example, if an external antenna type is configured by the user, but an internal antenna is actually detected by a receiver, the Positions Mobile extension will select a default internal antenna type for that receiver for collected sessions. Please note that the user-selected antenna type in the GNSS Settings page will not be changed if a mismatch is detected.

Further, Trimble Positions allows only one antenna type to be used per session. To enforce that, if the Positions Mobile extension detects an antenna disconnect while collecting a session, it will stop logging positions until the original antenna (external or internal) is reconnected. An appropriate “Reconnect antenna” message will be displayed.

When using a rangefinder, the antenna height should be set to denote the distance between an antenna and the center of the rangefinder’s lens. The rest of the height difference between a feature and an antenna will be calculated as part of an offset’s vertical distance component.

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