Differential Corrections: TerraStar (RT3000 v3 and RT3000 T v4)

Overview

TerraStar is a family of global GNSS correction services provided by NovAtel. These services deliver precise positioning corrections via L-Band satellite or internet (IP) to improve standalone GNSS accuracy from meters to just a few centimeters.

The RT3000 v3 and RT3000 T v4 devices include NovAtel OEM7720 receivers, which are compatible with the TerraStar-C Pro correction service.

Using TerraStar enables a device to operate in Precise Point Positioning (PPP) mode, improving positional accuracy for applications where RTK or local base station corrections are unavailable.

Requirements

To use TerraStar-C Pro corrections, you must have:

• An RT3000 v3 or RT3000 T v4 device

• L-Band capable antenna(s), ideally with L1/L2/L5 compatibility

• An active TerraStar-C Pro subscription

  • This can be purchased from your local NovAtel dealer - contact sales@oxts.com for assistance with this.

Configuration

Set up TerraStar corrections as follows:

1. Connect the device to a PC, open NAVconfig, and navigate to Hardware → GNSS Differential Corrections.

2. Enable TerraStar by selecting Automatic under GNSS Differential Corrections.

   • Manual beam selection is only needed if a specific beam must be tracked.

3. Enable TerraStar logging in Advanced Options to monitor status and troubleshooting:

->gps1: LOG TERRASTARSTATUSB
->gps1: LOG TERRASTARINFOB ONCHANGED
->gps1: LOG LBANDTRACKSTATB ONTIME 1
->gps1: LOG LBANDBEAMTABLEB

5. Commit the configuration to the device.

Activation and Convergence

After configuring TerraStar, the unit must be powered and have a clear view of the sky to receive the activation signal. Activation can take up to 60 minutes, with the TerraStar satellites rebroadcasting the signal every 2–3 hours if it is missed.

Once the activation signal is received, the receiver applies corrections and begins PPP convergence, which typically completes within 3–10 minutes under open-sky conditions.

Key points to note during activation and convergence:

• From firmware version 240917 and newer, the device will automatically switch to tracking triple frequency (GPS L1 C/A, L2P, L2C, L5; Galileo E1, E5b; BeiDou B1, B1C) when TerraStar is enabled to aid convergence times, however it will stop tracking GLONASS.

• To verify TerraStar operation, check Position Mode in NAVdisplay:

  • PPP (Mode 31) indicates full PPP correction is active.

• If PPP mode does not appear after setup and activation, contact support@oxts.com.

Considerations

PPP via TerraStar offers high-accuracy GNSS positioning, but users should be aware of the following:

• GNSS Tight Coupling Disabled: Enabling PPP disables GNSS tight coupling, which can affect INS performance in challenging GNSS environments.

• Reconvergence Required: If the unit loses position lock, PPP must reconverge, which can take several minutes and lead to poorer data quality.

• Recommended Approach: For reliable high-accuracy positioning, particularly in dynamic tests or areas with intermittent satellite visibility, RTK/NTRIP corrections are preferred when available.