Lidar for public safety and surveying


This page explains how drone-based lidar systems can be used in public safety tasks. This includes applications such as road collision reconstruction, crime scene reconstruction, natural disaster risk mitigation and disaster recovery.

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× DJI L1

The latest LiDAR scanner from DJI

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× DJI Matrice M300

DJI's latest and most advanced enterprise UAV

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× DJI L1

The latest LiDAR scanner from DJI

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× DJI Matrice M300

DJI's latest and most advanced enterprise UAV

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Drone-based LiDAR solutions


UAV lidar is complementary to photogrammetry-based drone solutions and has a number of advantages. It can be used, for example, B. without external light sources, as the laser pulses are not dependent on an external light source. In addition, the speed at which the data can be processed is much higher than with photogrammetric methods and takes only minutes instead of hours. The amount of data is much smaller compared to optical sensors, which allows for easier and faster storage as well as transmission.

Lidar is also particularly useful for vegetated areas, as the sensor can reconstruct the Boden beneath the vegetation, as well as the canopy. This is not possible with optical sensors and photogrammetric Bcalculations. Lidar is able to capture fine details, e.g. B. of complex objects, while photogrammetry would tend to smooth out these objects.

As lidar is laser pulses and not photographs, this is a great advantage for privacy as faces and personal information are not captured, which means there are fewer restrictions on flying.

DJI recently unveiled its first drone-based lidar solution: the Zenmuse L1. It will be mounted on the Matrice 300 RTK (M300 RTK), the company's flagship DJI-drones for industrial applications, and enables a flight time of about 40 minutes. The drone is equipped with an RTK module and can use satellite data for georeferencing the flight or sensor trajectories. This results in surveying accuracies in the FIX Brange.

Officially, the L1 can achieve an absolute horizontal and vertical accuracy of 10 cm and 5 cm respectively. However, in tests conducted by Epotronic we have measured an absolute vertical accuracy of 2.1 cm for a flight at 50 m altitude and 5.1 cm for a flight at 100 m altitude, together with a vertical precision of +/- 3 to 5 cm and +/- 7 to 11 cm respectively. It should be noted that the horizontal accuracies differ from the vertical accuracies by a factor of at least 1.5 to 2.5.

The L1 is equipped with a low-resolution RG B sensor that allows the point cloud to be coloured in true colour. If privacy is a concern, this should be turned off, which can be done in the flight app: DJI Pilot. However, the low resolution of the camera compared to a photogrammetry solution such as the Zenmuse P1 means that privacy is not as easily breached, for Bexample when flying at high altitude. For more information on privacy issues when flying drones, see our other article "Vorschriften für Drohnenflüge" or our knowledge section "Gesetze".

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× DJI L1

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× DJI Terra

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× DJI L1

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× DJI Terra

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DJI Terra can be used for almost the entire workflow of the L1. Flight plans can be created and executed, and the point cloud can be displayed in real time while the drone is still in the air collecting data. BThis allows for quick decision-making, which is crucial for public safety missions Bedeutung. Once the drone mission is complete, the point cloud can be processed in DJI Terra to create an accurate, dense point cloud and 3D model. Processing can be done in a matter of minutes with just a few clicks, with some settings such as reconstruction quality and output coordinate system to choose from.
The entire workflow is one of the easiest to use on the market. However, for exact and optimised results, we recommend further software, which we provide as part of our Schulungen.



To see exactly how lidar data is processed in Terra, please watch our youtube video.

Watch Video

The data can be exported from DJI Terra in common file formats, such as LAS. Exporting the point clouds allows seamless import into programmes capable of a variety of post-processing tools such as LiDAR360 from GreenValley, which can produce DEMs, contours, point classification and much more.

3D model generated in DJI Terra

Now that you are aware of the solutions available for lidar missions, we can get into the specific applications within public safety, where drone-lidar can provide large benefits.

Use cases



Crime scene and road collision reconstruction

UAV lidar can be of great benefit to crime scene and road collision reconstruction. Police services need to have a good overview of the scene, so that they can move forward with their investigation. Additionally road collision reconstruction helps determine what happened, who was at fault, and who is liable for costs and/or damages. Traditional photos and drawings are limited in their reconstruction accuracy, failing to capture the scene from all perspectives, especially above. Also for crime scene situations, the risk of compromising the evidence is lower compared to investigators that have to explore the scene by foot. This documentation is also traditionally time consuming; for road collision incidents, quick documentation by drones allows for the road to be cleared more quickly, reducing traffic congestion, and for crime scenes, faster progress with the investigation. 

Photogrammetry drones are already used for this use case by many police and emergency services, however lidar holds several advantages. For incidents that happen during the night, the lidar is able to capture the scene just as well as in the day, whereas photogrammetry would require artificial lighting, which increases operational costs and time. Additionally, the model can be produced much quicker than a photogrammetric model, enabling for swifter analysis and action. The privacy benefits of lidar also apply here, as things such as faces and number plates are not captured. If permissions are granted, users can still use built in cameras, such as on the L1, to simultaneously take photographs, allowing the point cloud to be colourised in real colour. In some situations, such as road collisions where there is a risk of explosion, using drone also provides a large safety benefit, as emergency workers do not need to be close to the scene to take photos etc.

The image above is an example of a firefighter using a drone for a road collision reconstruction.

Natural disasters



Mitigation

Drone lidar can also be useful in the Bmanagement of natural disasters by supporting Bmitigation and recovery efforts. The creation of accurate 3D maps of areas can enable analyses of disaster risk. BIn low-lying areas prone to flooding from rivers or the sea, for example, an accurate 3D map with correct elevation data (possible with the L1 and M300 RTK) can be created. Bhe map could be a digital elevation model (DEM), which can be created from the point cloud generated by the drone in post-processing software such as LiDAR360. For more products that can be created with drone data, see our other article "A guide to drone survey data" in our Blog. The DEM can then be imported into GIS software such as ArcGIS or QGIS where flood risk analyses can be carried out. This could then be used as the basis for mitigation decisions, e.g. B. for Bau of defences or not Bau of buildings in high risk areas. Similar workflows could be carried out for other natural hazards such as landslide and avalanche risk areas, volcanic eruptions, etc. The key is accurate 3D data, which is possible with the L1 and M300 RTK. In addition, the use of drones and thus Lidar allows for very high efficiency, especially in areas that are difficult to access. Thanks to the reduced data storage and processing requirements, even large areas can be surveyed and analysed without excessive computer hardware.

The Bimage on the left: Floods can be contained with drone lidar data

Immediate measures

In addition, drone lidar data can be used in disaster relief and response. When a disaster strikes, the first action is search and rescue. Time pressures are extremely high at this time, and responders need as much useful information as possible to figure out where to focus their Befforts and how to get there. Drones can be deployed and flown quickly to capture the Bnature of the area. Manual flights with live camera feedback are useful but limited at night when the range of Billumination is limited. Lidar data can cover large areas and the data can be processed quickly so that results are available within minutes. The real-time display of lidar data in DJI Terra will also be possible in the near future. This also means a great improvement in safety for search and rescue forces and civilians at risk.


Reconstruction

Later in the post-disaster period, when the focus is on clean-up and reconstruction, the use of drones is also very useful. After a flood, earthquake or tsunami, for example, the surface of the Boden may change and areas may no longer be suitable for Bevelopment. Drone lidar data can be used to reconstruct the area quickly and efficiently, and products such as DEMs and contours can be created to inform which areas are suitable. Change detection tools could also be used if pre-disaster surveys were conducted that clearly show where the land surface has changed. In addition, cadastral surveys (to Bestablish the location of land boundaries) would need to be carried out, which can be done with high accuracy using drone sensors such as the Zenmuse L1. Once this is determined, more general Bau surveys need to be carried out, which can also use drone lidar.

The Bimage on the left: Drone lidar data can help with disaster recovery

Conclusion


The use of lidar in public safety operations Ballows for a significant improvement in efficiency and an increase in information compared to conventional techniques. Response times can be reduced to save lives and prevent further damage. Decision-making is more robust as a larger and more reliable source of information is available, which also reduces the risk of wrong decisions.

Drone data can be used in a variety of applications, such as B. in reconstructing road collisions and crime scenes, and in mitigating and Brecovering from natural disasters. The use of drones improves the safety of personnel and victims and enables more accurate risk mitigation. The use of lidar has the added advantage of more flexible acquisition, e.g. B. at night, fast processing and analysis of data, which is crucial Bin emergency situations, less strain on computer hardware, the removal of legal restrictions on Be privacy and the ability to capture more detail, e.g. B. in overgrown areas or complex objects.

Bo find out more about the drone solutions described here, visit our online shop at shop.epotronic.com. There you will also find a lot of relevant information in our Blog.

If you have any questions, please do not hesitate to contact us at info@epotronic.com.


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