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Setting Up the Avular Stellar Base Station

This guide provides step-by-step instructions to set up and start using the Avular Stellar Base Station for high-precision GNSS positioning. An RTK (Real-Time Kinematic) base station works by receiving GNSS signals and calculating its precise position over time. The longer the base station remains stationary and measures its position, the more accurate its calculated position becomes. This process is known as survey-in. During the survey-in process, the base station collects GNSS data to determine its exact location.

The duration of the survey-in process can be significantly affected by weather conditions and the surrounding environment. For instance, conducting a survey-in on an open field with a clear blue sky can result in a much faster survey-in due to optimal GNSS signal reception. Conversely, a cloudy sky or an environment with many surrounding buildings, trees, or other obstructions can lead to a slower survey-in process. These factors can interfere with the GNSS signals, making it harder for the base station to accurately determine its position. Therefore, for the best results, choose a location with minimal obstructions and favorable weather conditions.

Once the survey-in is complete and the base station has a fixed, accurate position, it becomes operational. At this point, the base station starts sending out RTK correction messages to rovers via radio messages. These correction messages enable the rovers to achieve high-precision GNSS positioning by correcting their own GNSS data based on the base station's fixed position. It is crucial that the base station remains stationary during the survey-in process and while it is operational to ensure the accuracy of the RTK correction messages. Moving the base station during operation will result in biased correction data, leading to performance degradation of the GNSS position accuracy of the rover (Origin or Vertex).

Operational modes

The Stellar base station offers flexibility in terms of deployment, allowing you to operate it in various locations or set it up as a semi-permanent solution. All situations boil down to desired accuracy and the time spent in the survey-in mode of the base station. By default, the Stellar base station comes configured in the "normal" mode, which is a balance between survey-in time and obtained accuracy. Furthermore, Avular supplies two more preset configurations that the user can use.

The survey-in configuration consists of two main parameters. The survey-in mode ends if both conditions are met, the base station will automatically transition to sending out RTK correction messages. These two parameters are:

  • Minimum observation time: i.e. the minimum time the survey-in mode is to be activated before this condition is met. By default this is set to 10 minutes.
  • Required position accuracy: i.e. the standard deviation position data threshold that the survey-in mode must meet. By default this is set to <0.5 meter.

It is important to note that both conditions must be met for the survey-in process to complete. For example, in the accurate mode, both the required position accuracy of <0.1 meter and the minimum observation time of 8 hours must be satisfied. However, depending on environmental factors and GNSS signal quality, it might take up to 24 hours or more to achieve the required position accuracy. Patience and optimal placement of the base station are key to ensuring the highest accuracy.

Avular provides three different preset configurations for the Stellar base station, each tailored to specific deployment needs and accuracy requirements:

  • Standard deployment using normal mode:
    • The Stellar base station is shipped with this configuration, which is a compromise between speed and accuracy and can be used for most deployments with Avular robots.
    • Minimum observation time: 10 minutes.
    • Required position accuracy: <0.5 meter.
  • Long term deployment using accurate mode:
    • Optimal configuration for high position accuracy of the rover without compromise on the survey-in time. Typically used for semi-permanent deployment of the Stellar base station on for example a roof of a building.
    • Minimum observation time: 8 hours.
    • Required position accuracy: <0.1 meter.
  • Fast deployment using fast mode:
    • Typically used when no hard requirement is set on the accuracy of the base station and thus resulting on a lower position accuracy of the rover. However, this setting is very beneficial when you require a fast deployment and a remote site to quickly get up and running.
    • Minimum observation time: 5 minutes.
    • Required position accuracy: <1 meter.

Please consult the following instructions to change the configuration of the Stellar base station

If you desire to create a permanent deployment of the Stellar base station at your deployment site, you can opt for using the fixed mode of the base station. In this scenario, it is recommended to create a permanent fixture attached to a roofing structure to mount the base station or purely the antenna's and have the base station mounted indoors using antenna extension cables.

In order to correctly use this mode, a more precise point positioning survey-in method is advised to be used than one that is by default supplied by Avular. It requires to record a long dataset and use RTX Post-Processing to get a millimeter accuracy on the base station position. Please contact Avular if you wish to pursue this and we will help you achieve this.

Setup guide

1. Choose a proper position

Select an open area where the GNSS antenna has a clear view of the sky, clear of large tall elements such as trees, buildings. For long-term deployment of the base station, installing the base station on the roof of a building is recommended.

2. Assemble the Base Station

For the assembly of the base station, please consult the shipment contents and base station module overview for component naming.

  • Unfold and extend the foldable tripod stand to the desired height, fully extended is recommended. Please consult the tripod user manual for instructions how to unfold, extend and collapse the tripod.
  • Mount the Stellar base station module on the tripod using the UNC 3/8-16 threaded interface.
  • Connect the RTK radio antenna to the — 1 · DATA ANT — designated connector. Fold the antenna such that it point upwards.
  • Screw the GNSS antenna on the GNSS antenna mounting interface of the Stellar base station module.
  • Connect the GNSS antenna and the Stellar base station module with the GNSS antenna cable. One side installs on the — 2 · GNSS ANT — designated connector, the other side to the connector on the GNSS antenna.
  • Assemble the power supply:
    • Insert EU AC power cable in to the AC/DC 12V power converter.
    • Screw the mating connectors of the DC power cable and the AC/DC 12V power converter together.
    • Insert the mating connector ot the DC power cable into — · PWR · — designated connector on the Stellar base station module.

    Warning

    Important note: The AC-DC 12V power converter is not weatherproof due to the EU AC power cable.

  • The image below illustrates the fully assembled Stellar base station after completing the setup instructions.

Base station setup

3. Position the base station

  • Place the base station in the chosen spot.
  • Keep in mind that during survey-in and operation the base station is not to be moved. So choose a stable position before powering the base station.

4. Power the base station

  • Plug the EU AC power cable into a designated wall outlet.
  • The LED status bar will display on the left a green LED to indicate the module is properly powered.

5. Survey-in mode

  • The Stellar base station will immediately start the survey-in mode once powered. A red LED in the middle of the LED status bar will indicate the GNSS receiver is active.
  • Let the Stellar base station complete the minimum observation time, per default this is set to 10 minutes. Once this condition is met and the position accuracy is also met, the base station starts transmitting RTK correction messages over the radio.
  • Optional: checking survey-in status using the GNSS receiver software.
    • For first time use, you'll need to install the accompanied software of the GNSS receiver on your laptop. Follow the instructions here.
    • Next follow the instructions of the U-center user guide for connecting to the base station and then for polling messages.
    • For assessing the status of the survey-in mode, you navigate to messages view > UBX > NAV > SVIN (survey-in) to visualize the progress. That is, the elapsed time "Observation Time" and the current position accuracy "Mean 3D StdDev" values.
  • The device will begin receiving GNSS data and learning its position.
  • Ensure the base station remains stationary during this process for accurate positioning.
  • GNSS reception is shown by a blinking blue LED in the middle of the LED bar.
  • A blinking green LED on the left side of the LED bar shows that the radio is transmitting messages, including RTK correction messages once the position is learned.

6. Operational condition

  • Starting operation with a measured-in base station is simple, operate an Avular rover device (Origin or Vertex) within the radio link range (i.e. ~1.2 km). The rover will start automatically fusing the RTK correction messages into the positioning algorithm running on the rover device.
  • In the case of using an Origin, you can simply check on the user display if RTK is fused into the positioning algorithm. This will be indicated by the RTK text displayed in green or orange.