Exploring the idea of an ideal SAR drone altitude

Deploying many drones and teams isn’t a guarantee of increased Probability of Detection (POD) when searching for missing persons. However, using proven techniques that leverage the sensor fusion aboard a search and rescue (SAR) drone’s gimbal payload makes a significant difference. 

Easily portable drones and agile first responder teams can revolutionise traditional SAR. Training and technique make an enormous difference, as proven by real-world research and SAR development in a demanding environment – Norway. 

With its severe snowfall, heavy rain, and low cloud base in winter, traditional SAR air assets, like helicopters, can struggle in Norway’s challenging mountain and forest environment due to terrain risk and visibility limitations. In 2019, the Norwegian Joint Rescue Coordination Centre (NJRCC) recognised the potential of using SAR drones, deployed with local police SAR teams, to enhance its localised capabilities. 

Underwhelming drone SAR missions

Results were poor during the initial trial period, with a success rate of only 0.11 persons found per drone police pilot. The problem was identified as a technique and training issue. To increase the Probability of Detection (POD) during the SAR missions, Norwegian police teams and their drone pilots needed to learn how to optimize the available technology, adapting flight protocols to best operate with gimbal sensor payloads. 

Search effectiveness depends considerably on how much area can be covered quickly with an adequate resolution sensor payload. Gimbal angle, field of view ( FOV), flight altitude, search patterns and flight speed influence POD, illustrating the value of true sensor fusion. 

Optics, cameras, distance sensors and laser rangefinders work together to improve SAR drone operations and enhance missing persons’ POD. Sensor fusion is about enabling stable flight, collision avoidance, and enhanced sensing abilities when operating in hazardous terrain and weather conditions, which are often features of SAR missions. 

Improving SAR drone mission effectiveness

After a year of training and trialling different techniques, The Norwegian Joint Rescue Coordination Centre reported dramatic improvements in its SAR drone operations and POD. There was an eightfold increase in missing person discoveries, from 0.11 finds per drone pilot before the enhanced training to 0.88 finds after. 

How did the Norwegian SAR authorities and police improve their POD so dramatically? Rethinking SAR  drone altitudes. Although most drones are capable of impressive altitudes, flying higher might theoretically increase the field of view, but it’s not the best technique for precision search – or spotting missing persons on a live feed screen. 

What Norwegian SAR specialists discovered, operating in their demanding environment, was that lower altitudes work better in most searches. At a flight altitude of 100m above ground level, there’s a great balance between POD and search speed, regardless of search pattern. 

Using 100m of flight altitude as a standard during SAR, The NJRCC and police achieved a remarkable improvement in their SAR missions. From struggling during the initial SAR drone trials in 2019, to an 800% improvement in missing person detections in 2023. 

What are the insights from the Norwegian experience for global SAR operations? Flying lower is often better. That has implications for drone and gimbal sensor payload selection, proving that compact drones with mid-range sensors, have all the capability for excellent SAR mission success, operating at 100m above ground level. 

The laser rangefinder you need 

When selecting distance sensors and laser rangefinders as part of an SAR drone’s gimbal sensor payload, operators can reference the Norwegian experience, where 100m of recommended flight altitude has delivered outstanding results. That means that the benefits of  ultralight microLiDAR® sensors and mid-range laser rangefinders, can provide all the capabilities needed at lower weight, benefitting flight endurance. 

LightWare has an extensive product portfolio of microLiDAR® sensors, to fulfil SAR drone altimetry and terrain following needs. SF30/D, SF20/C, and LW20/C are microLiDAR® products designed to bring active terrain following capabilities on-board your drone. These ultralight microLiDAR® sensors enhance awareness and enable active terrain following, allowing confident flight across challenging and unfamiliar areas during SAR missions. 

The Norwegian experience is also particularly relevant to LightWare’s new GRF-250 laser rangefinders. It’s our latest product development, fulfilling the need for an ultralight mid-range laser rangefinder operating in the low-flight SAR drone role. 

With 250m ranging abilities and compact 10.65g design, GRF-250 is ideal for low-altitude SAR missions. An ultralight laser rangefinder designed to operate at lower altitudes and closer ranges, where Norwegian SAR teams achieved dramatically better POD results, GRF-250 enhances depth perception, detection and assists with localisation.

Learning from the real-world example of how successful Norwegian SAR teams have been, operating at 100m above ground level, procurement staff at government agencies and law enforcement departments can rethink real-world needs and what they require from a gimbal-integrated laser rangefinder for drone fleets operating in the SAR role. 

LightWare offers an extensive SAR drone sensor suite. Our growing product range of microLiDAR® sensors and GRF-250 laser rangefinders are ideal for SAR drone applications. 

The experience with global commercial drone customers created a market awareness at LightWare that mid-range laser rangefinders, with excellent gimbal sensor integration and low weight, were needed. This is why LightWare’s product team invested in developing the GRF-250, creating a laser rangefinder to serve as the gimbal sensor payload solution for SAR drones, at that crucial low-altitude flight pattern.