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u-blox-capture

Fork of SpectacularAI's repository. Added functionalities enable the scripts to output more information about the state of the GNSS tracking (eg. info related to RTK).

Building

str2str is used to send RTK ground station information to u-blox device.

cd RTKLIB/app/str2str/gcc/
make

Usage

Configuration

ubx_configurator.py can be used to configure the u-blox device. example/ folder contains some example configurations that can be used. definitions/zed-fp9-interface-description.txt contains supported configuration values. It's not comprehensive, you can add missing values from ZED-F9P Interface Description. Use -flash flag store changes to on-board flash memory, making them persistent.

python ubx_configurator.py /dev/cu.usbmodem14123301 example/high_precision_gps_only.cfg

Setting up RTK

Connect u-blox device and find what device it is. On Mac for example:

ls /dev | grep cu.usbmodem

On Linux the device is usually /dev/ttyACM0.

Next start str2str that connects to RTK ground station and delivers information to u-blox device.

You need to replace following with correct variables:

  • RTK information from your provider: USER, PASS, IP, PORT, MOUNTPOINT
  • LAT/LON: Rought estimate of current position
  • DEVICE: device name, for example: cu.usbmodem14123301 (leave /dev/ out).
./RTKLIB/app/str2str/gcc/str2str -in ntrip://USER:PASS@IP:PORT/MOUNTPOINT -p LAT LON 0.0 -n 250 -out serial://DEVICE:460800:8:n:1

Leave this running on the backround.

u-blox device should now show a blinking blue light (connected to GPS) and solid yellow light next to it (connected to RTK).

Logging

Replace /dev/cu.usbmodem14123301 with your device.

python ubx_logger.py -v /dev/cu.usbmodem14123301

Converting to simple GPS coordinates

gps_converter.py is used to convert different UBX messages (PVT, TIMEUTC, HPPOSLLH) to accurate easy to use GPS coordinates. It takes the ubx-*.jsonl file created with ubx_logger.py as an input.

python gps_converter.py output/ubx-2021-01-16-17-22-16.jsonl

An example entry:

{
    "time": 1610810565.79965,    # UTC time in seconds
    "lat": 60.173692026,         # Latitude
    "lon": 24.803227458,         # Longtiude
    "altitude": 15.3108,         # Altitude in meters
    "accuracy": 10.364,          # Accuracy in meters
    "verticalAccuracy": 14.836   # Vertical accuracy in meters
    "velocity": {                # Velocity estimate in NED coordsys
        "north": -0.028,         # Meters
        "east": -0.056,          # Meters
        "down": -0.024           # Meters
    },
    "groundSpeed": 0.063,        # 2D ground speed in meters
    "speedAccuracy": 0.108       # Speed estimate accuracy in meters
}

Resources