Scan a bridge with Hovermap

With careful planning, producing a good quality bridge scan is fairly straightforward. However, Hovermap can experience SLAM slips when operating over large areas of water, so the mission must be planned carefully.

If a SLAM slip occurs while the drone is underneath a bridge where the GPS signal is severely degraded, the system may be unable to transition to GPS mode. In that scenario, manual control of the drone may be required.

Hovermap scanning a bridge

The recommended process is as follows.

What you will need

A drone with Hovermap mounted.
Emesent Commander installed on the tablet, with a working connection to Hovermap.
Familiarity with Pilot Assist mode and the Shield feature.
A safe and controlled take-off and landing area on one side of the bridge.

Procedure

Step 1: Complete pre-mission checks

Complete the required pre-mission checks.

For background on how Hovermap automatically determines the most suitable navigation method based on the environment.

Step 2: Perform the mission

Perform the scan in Pilot Assist mode and keep the drone within visual line of sight for the entire mission.
Start and finish the mission on the same side of the bridge. This is the home point, so ensure it is in a safe and controlled area.
Enable Shield, then test it by trying to land the drone. Shield prevents the drone from landing.
Fly the drone so that Hovermap is facing the bridge at all times. This ensures Hovermap has a distinct feature in its sight, which prevents SLAM slip. Avoid turning the drone so that Hovermap faces open water.
While scanning, check the live point cloud in Emesent Commander to ensure data is being collected correctly.
Fly at a distance of around 5 m to 10 m from the bridge, staying roughly level with the street.
When the drone reaches the other end of the bridge, turn it 90 degrees so that Hovermap can still see the bridge. After turning, fly underneath the bridge.
Be careful not to fly too close to the underside of the bridge, so the drone retains a good GPS signal. Dipping the drone slightly can help it retain a clear view of the sky.
When the drone reaches the other side of the bridge, turn it 90 degrees again so that Hovermap continues to face the bridge.
Fly the drone back along the same approach used on the other side. Stay at street level and a distance of 5 m to 10 m from the bridge, with Hovermap facing the bridge at all times.
Fly below the bridge and return to the home point to land.
Download the scan folder from Hovermap.
Perform a second mission if necessary.

If the drone is fitted with a camera, having a second operator to control the camera lets the pilot focus on flying the system.

Outcome

The bridge has been scanned and the scan data has been downloaded from Hovermap, ready for processing in Aura.

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