GPS - RTK Base Station
RTK Base Station
The RTK base station will be the stationary module providing the RTK corrections to the GPS RTK module in the rover. This module will be remain outside in all weather conditions, so a weatherproof case is required.
I have been testing this 3D printed base station case for the past 8 months. It has survived rain, snow and gale force winds. It uses the natural shape of the 3D print to keep out water and weather and works really well.
If you decide to use this case the STL Files for this base station can be downloaded here:
RTK Base Station Case Overview
The base station board is powered by a 3.7-20V DC Power Supply. I used a 12V supply to power the base station. 2 SMA extension cables link to the outside of the case (not provided in the application board set) where the antenna for the radio transmitter and waterproof GPS satellite module (provided in the UBLOX application board set) are connected to the case.
Positioning the RTK Base Station
The RTK Station needs to be positioned so that the Rover will have the best line of sight to the base station. This will aid the radio transmissions from the base station to the rover. The GPS antenna should have an open view of the sky and not be close to buildings, trees other objects which are taller than the GPS Antenna position.
If you have an open garden with few obstructions then the RTK base station will work well in most positions. If your garden has lots of nooks and shielded areas (e.g. by garages) then you need to carefully consider the position of the station and test for best results.
Setting up the Base Station
To configure the base station we need to:
1. Tell the module it will be acting as a base station
2. Let the module search for its location
3. Tell the module to start transmitting the RTK correction data via radio
4. Tell the module to send the right types of GPS messages.
To do this we are going to use the UBLOX U-Center software.
Setup Guide
The UBLOX C94-M8P-2-10 comes with a very clear starter guide.
I also found this video very useful from iforce2d on youtube..
Follow the guides to set up the modules.
My Setup Tips:
- Ensure you Connect the Antenna and GPS Module first before giving power to it! You shouldn't run the module without the antennas attached as this can damage the module
- Download the U-Blox U Center Software and get familiar with it
- Dont mix up + and - when attaching the board to the 5V power. This will damage the module!!
- For the survey in i used 0.7m as the goal for the accuracy.
- I also disabled all NMEA messages in the base station module and enabled UBX > NAV > PVT Messages as in the iforce2d video. Without this I found that the TIME message was not displayed after the survey in.
- Note down the X Y Z Fixed Position numbers after the survey in. (screenshot). These can used if there is a power loss to the module without the need to survey in again.