Antenna Placing

Placing the RTK Antenna is very important for getting precise RTK positioning

Normal GPS positioning, only requires you to place the device near a window and it will provide you a GPS location over a period of time. But that’s not enough for RTK. For the working environment of RTK, there are special requirements on antenna placement, which are much more stricter than GPS.

The best environment for the base and rover antenna is a clear view of the sky that is 30 degrees above the horizon. RTK antenna can be elevated but ensure that there are no obstacles around, such as buildings, trees, cars, and etc

Examples of bad environments: indoors, urban areas, forests, or near the ground.

Examples of good environments: Open spaces, peak of a mountain, roof of a building.

Do not place the antenna near electronic devices, as high power electronic devices in close proximity may affect the radio frequency noise of the GPS signal. Examples are mobile phone base stations, high voltage transformers, etc.

Please place the base station in an outdoor environment with sufficient sky coverage to obtain a good satellite signal.

Place the base station on a stable and elevated platform, such as a tripod.

Base Module Setting using Mission Planner

Start with a base module setup first. During the base station setup, the rover and the UXV do not need to be turned on.

Open the Mission Planner ground station software on your computer and go to the “initial setup → Optional Hardware → RTK/GPS Inject”. You will see the following page:

Select the correct base module com port in the top left corner and click ‘connect’. In the SurveyIn Acc section, enter the absolute geographic accuracy that you expect your Here+ base station to achieve. In the Time column, enter the minimum survey time you expect. Click on Restart, the ground station will transfer the data you have entered to the base module, the base module will start a new round of surveying. You will see the following page:

During the survey process, the right box will show the current survey status:

The Position is invalid: The base station has not yet reached a valid location;

In Progress: The survey is still in progress;

Duration: The number of seconds that the current surveying task has been executed;

Observation: the number of observations acquired;

Current Acc: Absolute geographic accuracy that the current base station can achieve;

The Green bar at the lower part of the Mission Planner page shows the current satellites being detected and the signal strength related to each satellite. At least eight or more satellite signals need to be guaranteed to exceed the red line (Only when the satellite signal exceeds the red line, the effective number of satellites have been connected).

The base station needs a certain amount of time to meet the accuracy requirements of your input. Testing shows that in an open area without sky coverage, the base station will achieve the absolute accuracy of 2m within a few minutes; to reach the absolute accuracy of less than 30cm takes about an hour; to reach the absolute accuracy of 10cm takes a few hours.

It should be noted that the absolute geographic accuracy of the base station here will affect the absolute geographic accuracy of the rover module without affecting the relative accuracy between the base station and rover. If your application does not require UXV with high absolute geographic accuracy, you do not need to set the base station’s precision too high, which helps to avoid a longer survey time.

Even if the accuracy of the base station is 1.5 to 2 m, the position accuracy of the rover module relative to the base station can still reach the centimeter level.

After the survey is complete, the Mission Planner will display the following page:

In the RTCM box it shows that the base status indicator is green and both GPS and Glonass satellite systems are green (if you want to change the satellite system, refer to the following section). The box on the right says “Position is valid”.

To store the current location in Mission Planner: Click “Save Current Pos”, enter a name in the dialogue box, and click “OK”. As shown below, you can see your saved location in the list. Click the “Use” button for the location you saved. The base station will enter the fixed mode and the status will show “Using FixedLLA”. In the future, if you set the base station in the same location, you do not need to conduct the survey again, just click the “Use” button that corresponds to the location you have saved.

Rover Module and Flight Controller Setup

Once the base station is established, you can activate the UXV. By utilizing the same telemetry module to connect with Mission Planner, the base station data will be transmitted through the telemetry module to the Here4 rover module on the UXV. On the main page of Mission Planner, you will be able to observe the current GPS status, which will be indicated as either RTK Float, RTK Fixed, or 3D RTK. These indications signify that the UXV’s positioning has entered the RTK mode. RTK Float represents a floating-point solution, while RTK Fixed represents a fixed solution. RTK Fixed mode offers higher accuracy but requires a stronger signal strength. The term “3D RTK” is a comprehensive reference to both RTK Float and RTK Fixed in the Mission Planner interface.

Single Base to Multiple Rovers

There are 2 methods to do this:

1)  Use 1 telemetry to multiple telemetry broadcasting ;

or

2) Use multiple 1 to 1 telemetry modules with USB hub

Ground station configuration: connect all telemetry modules to the computer via USB hub. Open Mission Planner to locate the base then connect it with flight controllers. Select AUTO connecting as shown below. All recognized flight controllers on the ports will be connected. You may select the UXV from the dropdown list below:

If you connected the UXVs with 1 telemetry module, they should share the same COM port:

U-Center Firmware Update

Ensure that you have the latest firmware on Here4 before this process. Please follow #3.firmware-update to update the firmware.

Latest NEO F9P L1L5 firmware can be found here under Firmware Update section. https://www.u-blox.com/en/product/neo-f9p-module?legacy=Current#Documentation-&-resources

1. Inside DroneCAN/UAVCAN config page of Mission Planner. Select Menu and Check

If the following option is not visible in Mission Planner, then update Mission Planner to latest Beta from Help menu.

2. Select port for u-Center to connect on.

3. Select baudrate to set for ublox communication.

4. Open u-center (Ensure that its version 22.07+). Under connections select Network connections > New.

5. Set url to tcp://127.0.0.1:500.

6. Select Tools>Firmware Update Utility. Select the downloaded firmware from ublox website in the tool. Ensure that baudrate is same as set in Mission Planner. And Options are correctly selected as shown below. And then click GO.

Cubepilot Here 4 GNSS Manual