LiDAR scans: multirotor vs fixed-wing

LiDAR drones are becoming a common tool used across multiple industries, such as construction, transportation, planning, agriculture, oil and gas, power generation, etc.

One of the key parameters of LiDAR scans is a point cloud density, and depending on a particular task various 3D point cloud densities are required.

Let’s look at two examples - cell tower inspection and a large-scale land survey.

For both tasks, LiDAR drones are used but it is hard to have a single drone to perform both.

When inspecting a cell tower a very high-density cloud of hundreds or even thousands of points per square meter is required to reliably check the equipment, though when doing a large-scale survey for construction planning, a hundred points per square meter is enough.

At the same time, it is very important to precisely anchor a land survey to a mapping system used by the customer, while it is not usually required for inspection tasks.

So what would be the best solution for such different challenges?

A cloud density depends on onboard LiDAR frequency, distance to the object, and the drone speed. And if you are looking to collect data for a very high density - the multi-rotor drones are the best solution. They can carry heavier LiDARs with higher frequencies, they can fly very slowly and even hover to allow LiDAR to scan the same area many times, and with an experienced operator, multi-rotors can fly very close to an object of inspection.

But there are a few things that multi-rotors can’t do - flying fast and staying in the air for a long time.

A typical commercial multicolored with a powerful LiDAR can only stay in the air for little more than half an hour and has a cruise flight speed of around 25 mph. 

Thus it will require a multi-copter to do about 50 flights from a few different locations to LiDAR scan a 10,000-acre area (40 km2), making it a two-week-long job to just collect the data.

A fixed-wing drone like FIXAR 007 can scan the same area in just 10 flights from the same location. It makes it possible to complete the job in just one to two days.

This not only means less flight time than multirotor, but it is also five times fewer files to deal with during post-processing. 

Also, drones are equipped with RTK or PPK GNSS antennas to determine the exact drone location at any point in time. This allows to achieve mapping accuracy of 2-3 cm.

So while it is possible to LiDAR scan large areas with a multiopter it is not the most efficient way to do it.