Configuring the GNSS

To configure GNSS Settings, tap / Tools / GNSS Settings.

By default, SiteVision uses Trimble Corrections Hub to receive GNSS corrections. To use a local correction source such as a 3rd party or government virtual reference station network or Internet Base Station (IBSS), deselect Trimble Corrections Hub and enter the required information.

TIP – Use a local correction source when you are outside of Trimble Corrections Hub coverage areas.

NOTE – All correction sources must be connected to the internet and be accessed via the internet (Wi-Fi or mobile network data).

By default, the SiteVision system uses Trimble Corrections Hub to receive GNSS corrections. This provides you the best accuracy available wherever you are in the world using corrections from Trimble Positioning System's VRS Now networks and the Trimble CenterPoint® RTX service.

Trimble VRS Now coverage is available throughout many parts of North America, Europe, Australia, and New Zealand when using a compatible GNSS receiver. Trimble VRS Now fully supports GPS, GLONASS, QZSS (not all networks), Galileo, and BeiDou satellite systems.

Before using the Trimble Corrections Hub check your coverage on the Precision Coverage Map.

In areas with VRS Now coverage, the SiteVision system will typically achieve accuracies of a few centimeters.

If you are operating in an area that does not have VRS Now coverage, the Trimble Corrections Hub will select the RTX service.

When using the RTX services the horizontal accuracies will vary by location, but are typically 10 - 20 cm (4 - 8 inches) in areas with RTX Fast coverage, after convergence, and 30 cm (12 inches) in areas without RTX Fast. The vertical accuracy of the model placement may vary when using the RTX services. The RTX service has global coverage and is used in all areas that are outside of Trimble VRS Now coverage.

For applications where high vertical accuracy is required such as checking road construction status or utility locations, Trimble recommends that you use the VRS Now service, a 3rd party VRS service or an internet base station service.

TIP – By default SiteVision is configured to support working with high horizontal accuracies of < 5 cm. When working in areas where this level of accuracy is not available (e.g. when using the RTX or RTX Fast correction service) you will need to adjust the GNSS Minimum High Accuracy setting. This setting controls the minimum horizontal accuracy required to achieve a 'Green' GNSS icon, a requirement for many SiteVision workflows. To adjust this setting tap / Tools/ Configuration / Advanced.

When using Trimble Corrections Hub, by default the Target Reference Frame is set to the Automatic setting. This setting outputs positions in the most appropriate reference frame based on your current location. If your model appears to be positioned incorrectly, check with the provider of the data to confirm what datum the model is in, and set the target reference frame to match.

TIP – If you do not have an internet connection when you start the SiteVision system, Trimble Correction Hub connects you to the satellite-delivered RTX correction stream or to a local SBAS service. If this occurs and you re-establish your internet connection, you can re-start the GNSS service by tapping Save & Reconnect in the GNSS Settings dialog; the system restarts using the internet-provided corrections service (VRS or RTX over IP).

If you are working in an area outside of the Trimble VRS Now coverage zone, you may want to configure your own GNSS correction source.

The NTRIP setting allows correction data to be received securely from an NTRIP Caster. The NTRIP source may be one of the following:

  • A Trimble VRS Network

  • A Trimble NTRIP Caster

  • The Trimble Internet Base Station Service (IBSS)

  • Another NTRIP compliant correction source

To configure and use a local correction source via NTRIP:

  1. Deselect Trimble Corrections Hub.

  2. Enter the server parameters for the local correction source.

  3. Select the Source Reference Frame to match the reference frame of the VRS network or IBSS.

  4. Select the Target Reference Frame to determine the coordinate output.

  5. Tap Save & Reconnect to confirm your GNSS Settings.

  6. If the Source Reference Frame of your NTRIP Caster is not on the list of supported reference frames, then ensure the Target Reference Frame is set to Same As Source. This will output positions without applying any transformation (the Source Reference Frame setting is effectively ignored in this case).

TIP – If you tap Save & Reconnect when you are connected to the GNSS and receiving positions, your GNSS will restart/reconnect.

A VRS network or local correction source will be broadcasting coordinates in relation to a known reference frame. This is called the Source Reference Frame.

Trimble SiteVision is capable of performing real time datum transformations of GNSS positions. This allows SiteVision to receive positions from a VRS or local correction source, and output them in a specified Target Reference Frame.

This provides flexibility to work in terms of a local datum, or common global datums as needed.

  • Same as source: SiteVision will pass through positions as received by the receiver.

    • Trimble Corrections Hub dynamically adjusts the correction source to always provide the highest level of accuracy. For this reason it is not recommended to use the Same as Source setting in conjunction with Trimble Corrections Hub.

    • If you are using a local NTRIP source the positions will be in the same coordinate system as the local NTRIP source.

  • Auto Selection: SiteVision looks at the current position to look up the reference frame you are most likely in based on your current position.

  • User Choice (from list): Select a reference frame from the list of supported datums, and this will be the output reference frame.

A geoid model applies a vertical transformation to account for local variations in the earth’s gravity field. There are many different geoid models ranging from global geoids such as EGM96, to regional geoids such as EIGEN-6C4, or GEOID12B.

  • If your model data is in terms of a geoid model, then an appropriate Trimble Site Calibration file will be required to ensure your data is displayed correctly.

  • SiteVision supports custom, or sub-gridded geoid models. For detailed instructions see Using custom Geoid models.

 

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