Note
Please bear in mind that every situation is unique. These practices are a guideline only, and may need to be adjusted for your specific environment.
If planned correctly, it is fairly easy to produce a good quality bridge scan. However, it is important that you plan carefully, as Hovermap can experience SLAM slips when operating over large areas of water.
If a SLAM slip happens, and SLAM is your primary navigation method, your drone will lose its awareness of its environment and the ability to hold its position. This could result in the drone drifting uncontrollably in any direction. If GPS is your primary navigation mode, you will still lose your map and have to restart the mission. So, either way, it is essential that you plan your mission with SLAM in mind.
We recommend that you follow this process for the best results.
Step 1: Pre-mission checks
Set your navigation methods as follows:
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Good GPS signal: If you are likely to have a good GPS signal for your entire mission, set GPS as your primary navigation method and SLAM as your secondary method.
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Partial GPS signal: Set SLAM as your primary navigation method and GPS as your secondary method.
Go to Understanding Hovermap for more information on choosing the best navigation method.
Note
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SLAM is not as effective above water, so it is a good idea to use GPS as your primary navigation mode if possible.
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If you decide to use GPS as your primary navigation method, make sure that the drone will have a clear view of the sky at all times so that you aren’t at risk of losing GPS signal. If you need to fly too close or too deep underneath the bridge, it is better to use SLAM as your primary navigation method.
Step 2: Perform your mission
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Perform the scan in Pilot Assist mode and keep the drone within visual line of sight for the entire mission.
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Start and finish your mission on the same side of the bridge. This will be your home point, so make sure that it is in a safe and controlled area.
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Enable VESH and then test it by trying to land the drone. VESH should prevent you from landing.
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Fly the drone so that Hovermap is facing the bridge at all times. This will ensure that Hovermap has a distinct feature in its sight, which will prevent SLAM slip. Avoid turning the drone so that Hovermap faces open water!
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While scanning, check the live point cloud to ensure that your data is being collected correctly. Do this in the Hovermap App or the Waypoint UI (go to The Hovermap App for more information). You can also do this by connecting to the Hovermap’s Wi-Fi, opening a web browser (on any laptop or Android device), and then navigating to hover.map:8082.
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Fly at a distance of around 5 m to 10 m from the bridge. Stay roughly level with the street.
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When you reach the other end of the bridge, turn the drone 90 degrees so that Hovermap can still see the bridge. After you have done this, you can fly underneath the bridge.
Note: If you are flying with GPS as your primary navigation method, be careful at this stage not to fly too close to the underside of the bridge. This is so that you can retain a good GPS signal. In this situation, it helps to dip the drone a little bit so that it retains a clear “view” of the sky. -
When you reach the other side of the bridge, turn the drone 90 degrees again so that Hovermap continues to face the bridge.
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Fly the drone back towards you in the same way you flew it on the other side. Fly at street level, and at a distance of 5 m to 10 m from the bridge. Make sure that you face the bridge at all times.
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Fly below the bridge and return to your home point to land.
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Download the scan folder off your Hovermap.
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Perform a second mission if necessary.
Tip
If you are using your drone with a camera, it is a good idea to have a second operator to control the camera. This allows you to focus on flying the system.