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| Code Block |
|---|
"gnss": {
"type": "NMEA",
"settings": {
"port": "COM4",
"baudrate": 115200,
"rtcm": true
}
} |
Configure the ZED-F9P RTK-GPS module (only needs to be done once):
Download u-center
.
Make sure GGA, GSA and VTG messages are
enabled.
Before that, you need to choose “Receiver“ tab in menu bar, navigate to “Connection“ and connect to the correct COM port, then set the baudrate to 115200.
Next, navigate to “View“ → “Messages View“, right-click “GxGGA”, “GxGSA“ and “GxVTG“ text to enable them.
Then open “Configuration View“, choose “RATE (Rates)” to set frequency to 5Hz by changing measurement period to 200ms.
You can checkout the output of the RTK-GPS with “Text Console” to verify if the settings is effective.
The last step is to save the settings. Open “Configuration View“, choose “CFG (Configuration)“, select “Save current configuration“ and apply for all devices and then click “Send“ in the bottom left-hand corner to save the settings.
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Set up an NTRIP caster service by creating a free Emlid Flow account. Note that you only need the free version.
Set up the Emlid RS2+ base station. A detailed guide how to connect it to the internet using a SIM card is here: https://docs.emlid.com/reachrs2/rtk-quickstart/connecting-reach-to-the-internet/enabling-cellular-modem
Next, adjust the base station settings so that the base station outputs correction data to our NTRIP caster: https://docs.emlid.com/reachrs2/rtk-quickstart/base-rover-setup Note that we only need to follow the instructions on setting up the base station, the rover we set up via the FusionHub interface.
Configure the base station to talk to our Emlid Flow account: https://docs.emlid.com/emlid-caster/emlid-caster-base-rover-connection
Set up FusionHub to receive RTCM data from the Emlid Flow caster:.
For example if your caster configuration is the following:
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FusionHub should now output the status of the RTK-GPS connection to the command line. Note that currently we don’t yet output the status in the GUI. This will follow soon. There are three states to the RTK-GPS system:
GPS (RTK not connected, output has normal GPS accuracy)
Float (RTK connected and working, but not enough data to get high accuracy output)
Fix (RTK connected and in high-accuracy mode)
These three states are reported by the GNSS node as GnssData messages with the quality field:
Quality flag value | Name | Result |
|---|---|---|
2 | DGPS | The GNSS unit is operating as normal GPS unit. It is not receiving correction information from an NTRIP server or other RTCM source. |
4 | RTK fixed | The RTK-GPS system is locked and operating with ~2cm positioning accuracy. This is the desired state. |
5 | RTK float | The GNSS unit is receiving correction information from an RTCM source, but so far hasn’t been able to lock to high precision mode. There might not be enough satellites in view or the system needs more time to stabilize. |
Preferably we always want the system to operate in Fix mode. This requires working connection to the NTRIP caster, decent antenna placement and a sufficient number of satellites in view of the car’s antenna and the base station antenna.
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