Concept · NTRIP & VRS
GGA is a short position message your device sends to the NTRIP server. For standard mountpoints it is optional. For VRS mountpoints it is mandatory — without it the server cannot generate corrections and streams nothing back. This is the single most common reason VRS appears to connect but delivers no Fix.
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GGA stands for Global Positioning System Fix Data. It is one of several standardised NMEA 0183 sentences — short text strings that GPS and GNSS receivers use to report position and status information. You have probably seen NMEA sentences if you have ever looked at raw receiver output: they begin with a dollar sign and are comma-separated.
In the context of NTRIP, GGA has a specific role: it is the sentence your device sends to the server — in the opposite direction from the correction data — to tell the server where you are. This is unusual because most NTRIP communication is one-way (server to rover), but VRS requires this two-way exchange.
GGA does not need to be accurate to centimetre level for NTRIP to work correctly. A single or float solution position — accurate to a few metres — is more than sufficient. The server only needs to know which part of the network you are in, not your exact position.
A typical GGA sentence looks like this. Each comma-separated field carries a specific piece of information:
The fix quality field in GGA tells the NTRIP server — and any other system reading the output — what kind of position solution your receiver currently has:
| Value | Meaning | Typical accuracy | Suitable for VRS? |
|---|---|---|---|
0 |
No fix | — | No — position is invalid |
1 |
GPS fix (Single) | 2–5 m | Yes — good enough to locate in network |
2 |
DGPS fix | 0.5–2 m | Yes |
4 |
RTK Fixed | 1–3 cm | Yes — best quality GGA |
5 |
RTK Float | 0.1–1 m | Yes |
6 |
Dead reckoning | Variable | Depends on accuracy |
You do not need Fix before sending GGA
A common misunderstanding is that GGA only works when you already have RTK Fix. In fact, a Single solution (quality 1) is perfectly sufficient. Send GGA as soon as your receiver has any valid position — this allows VRS to start generating corrections, which then helps you get Fix.
The setting name varies between NTRIP clients, but the function is the same on all of them. Click your device to expand the instructions:
Go to . Tap your saved NTRIP profile or create a new one.
Enable the toggle labelled Send GGA to caster. This appears directly in the NTRIP configuration screen.
Tap Connect — wait until the receiver has a Single solution (at least one bar of satellite signal) before connecting. GGA with quality 0 (no fix) does not help the server locate you.
Go to . Enter your server credentials and select the VRS mountpoint.
Enable Transmit GGA. This toggle appears in the NTRIP client settings panel.
Tap Connect. SW Maps sends GGA from its internal GPS or from the connected external receiver — ensure the correct position source is selected in the app's device settings.
Go to . Use Data Collector as the internet source.
In the data source settings, look for GGA transmission or Send GGA to server and enable it.
FieldGenius sends GGA from the connected receiver. Ensure the receiver is connected via Bluetooth and has at least a single solution before tapping Connect.
Trimble Access sends GGA automatically when NTRIP is enabled — there is no separate toggle. When you enable Use NTRIP in the survey style's data link settings, GGA transmission is part of the NTRIP v2 protocol that Trimble Access uses by default.
If you see a message about a coordinate system mismatch when connecting to a VRS mountpoint, this is normal — dismiss it and continue. The corrections are in WGS84; your job coordinate system handles the transformation.
DJI sends GGA automatically once the drone has GPS lock outdoors. There is no manual toggle — GGA transmission is built into the DJI Custom Network RTK implementation.
You must be outside with a clear sky view before connecting. DJI will not send GGA indoors because the drone's GPS has no fix. If you connect indoors, the VRS server receives no valid position and returns no data.
After powering on outdoors, wait for the aircraft status to show GPS signal (typically 30–60 seconds), then connect to the NTRIP mountpoint in RTK Settings.
Open the app and go to Settings. Enable Send GGA to Server.
Set the GGA source: choose NMEA from Bluetooth device if you have an external receiver connected, or Android internal GPS to use the phone's own position. For RTK work, use the receiver's position — it is more accurate and updates faster than the phone GPS.
The GGA send interval is configurable — the default of 5 seconds is appropriate for most VRS services.
In the RTK rover profile, go to the network correction settings. When NTRIP is configured and the VRS or MAC mountpoint is selected, GGA is sent automatically as part of the network connection process.
Leica's MAC (Master-Auxiliary Concept) mountpoints work similarly to VRS but use a different server-side algorithm. Both require a valid GGA from the rover. Captivate handles this without a separate setting.
Connected to VRS but 0 bytes per second
The connection is established but no corrections are flowing. Almost always means GGA is not being sent — or is being sent with quality 0 (no fix). Enable GGA in your NTRIP client, ensure the receiver has at least a Single solution, then reconnect.
GGA sent but Fix is very slow
If GGA is transmitting correctly and corrections are flowing (bytes per second is non-zero) but Fix takes many minutes, the GGA position may have had low quality at the time of connection. Disconnect, wait for a better single solution outdoors, then reconnect. The server will generate a more accurate virtual station.
Moving between areas — does GGA update?
Most NTRIP clients send GGA periodically — every 5–60 seconds. If you drive more than a few kilometres while connected to a VRS mountpoint, the server receives updated GGA positions and adjusts the virtual station to follow you. You do not need to disconnect and reconnect when moving around the network coverage area.
Privacy note
GGA only contains your approximate position (metre-level accuracy from a Single solution), your altitude, satellite count and fix quality. It does not contain any personal identifiers. The NTRIP server uses it only to route corrections — it is not stored or shared in any way that identifies you.