This code will save raw GNSS messages in u-Blox's proprietary UBX format to an SD card connected to an Arduino microcontroller. The UBX data files can later be post-processed into precise positioning using software like RTKLIB. You can also use RTKLIB to convert UBX to RINEX format and then send the raw data to an online PPP service to do the processing for you. (Natural Resources Canada provide a good one)
In this way GPS/GNSS postions can be post-processed to better than 2 cm accuracy.
For a full description see our main project page at hollystill/LowCostGNSS.
u-Blox RAWX and SFRBX binary messages are written out once every 10 seconds. This should be fine for static installations, as well as those moving at glacial speeds. Many PPP services will decimate this to once every 30 seconds during processing anyway. You can set it to log once a second but the data files will start to get pretty big.
This code was written for the following hardware, but may be compatible with similar or more powerful boards.
- u-Blox high precision ZED-F9P RTK receiver board (Eltehs ELT0087)
We have also successfully tested it with the u-Blox C099-F9P application board - Arduino microcontroller Adafruit Feather Cortex M0 Adalogger (SAMD21 chip)
- I2C communication between the GNSS receiver and Arduino (address 0x42)
- A 12 volt battery connected to a solar controller and small 10 watt panel
The whole set up is relatively low cost and consumes around half a watt. A description and build instructions for the hardware is planned to be included in the hardware/ directory at a later date.
It uses the SparkFun u-Blox GNSS Arduino library, and was inspired by their included raw data logging example <DataLoggingExample3_RXM_SFRBX_and_RAWX> by Paul Clark (MIT licensed). A compatible version of this library is included in the contrib/ directory for posterity.
It also uses the Temperature Zero library by Electronic Cats and friends (MIT licensed) to read the Cortex M0's temperature. This is easily disabled if you are not using a SAMD21 or SAMD51 microprocessor.
Daily log files are written to the SD card in NOAA NGS naming style:
YYYY/MM/IIDDjjjn.UBX
Where YYYY is the year,
MM is the month,
IIDD is a user-definable logger ID,
jjj is the day of the year,
and n is the starting hour (UTC, presented as a letter A-X for 00-23).
Note we write out daily files not hourly ones, and break things up into monthly directories, so it's not exactly true to the NOAA NGS naming style.
In addition hourly status reports including basic positioning information, battery voltage, and the M0's temperature is written to a monthly status file called STATUS.LOG within that month's directory.
An analysis of the GNSS receiver and overview of the processing is given in Still et al. 2023 (J. Glaciology, DOI: 10.1017/jog.2023.101) based on a deployment in Terra Nova Bay and the Priestley Glacier, Antarctica.
This code is licensed under the GPL version >= 3. See the GPL-3.txt file found in the src/ directory.
The description of the circuit board and build instructions are licensed under the Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International (CC BY-NC-SA 4.0) license.
You may also find this project on Codeberg.org
Have fun! =)