Mayday mayday mayday! My GNSS antenna is out!

When talking about 3D scanners, a GNSS antenna is used to enable precise geolocation of the device during the scanning process. This feature is particularly important in mapping applications where geographic accuracy of data is essential. But what to do when we lose the signal?

What is a GNSS antenna?

A GNSS antenna, short for Global Navigation Satellite System, is a device designed to receive and transmit signals from navigation satellite constellations, such as GPS (Global Positioning System), GLONASS (Global Navigation Satellite System), Galileo and BeiDou. These antennas are used to receive the signals emitted by these satellites in order to determine their position, speed and time with great precision.

When a 3D scanner is equipped with a GNSS antenna, it can receive signals from navigation satellites and use this data to determine its own position and orientation in space with high precision. This allows 3D point clouds generated by the scanner to be georeferenced, ensuring accurate integration of the data into a global geographic coordinate system. As a result, users can obtain accurate, georeferenced 3D models of their environment, which is essential for many applications, such as urban planning, natural resource management and infrastructure modeling.

It's going to go off, I'm going under a tunnel...

A GNSS antenna is very sensitive to its environment and can encounter several problems that can affect its accuracy, including:

  • Signal obstruction: obstacles such as buildings, dense trees, or metal structures can block or weaken the GNSS signal, reducing position accuracy.
  • Multipath: GNSS signals can bounce off reflective surfaces before reaching the antenna, leading to measurement errors and inaccuracies in the calculated position.
  • Electromagnetic Interference: sources of electromagnetic interferences such as electronic equipment, cell phones or nearby power lines can disrupt the GNSS signal and affect position accuracy.

MS-96, the off-road expert

Although it may highly impact some mobile scanning systems, the quality of MS-96 data is not impacted by the loss of GNSS reception. This is thanks to 2 factors:

  • its high-end inertial measurement unit capable of taking over for several minutes during high dynamic use cases, only exhibiting minimal absolute drift
  • its SLAM technology capable of taking over in low dynamic contexts (canopy, urban canyon, etc.)

But what about environments captured with low dynamics (pedestrian, motorized at low speed) and without structures for SLAM? Here too, there is a solution. More information in a later article 😉

The proof is in the pudding

As part of a project aimed at evaluating a paid parking area, located both outdoors and indoors, we implemented the versatility of the MS-96 Viametris. The scanning process began outdoors, with the MS-96 installed on the roof of a moving car. Then, our technician continued on foot on the sidewalk, with the MS-96 carried in backpack mode, before continuing the scan on foot in an underground parking lot, as the vehicle equipped with the MS-96 mounted on the roof could not access the car park, due to height limitations. Here are the results obtained.