At Inflights we very often get the following question from our pilots:

“I want to invest in a new drone, which drone should I buy? Which payload do I need?”

These days, contrary to let’s say 10 years ago, there are a whole lot of very good and very affordable drones out there, from a wide range of providers. Rather than telling you which drone you should buy, we can tell you what you have to look for based on your specific type of work.

The drone and payload most suited to your needs depends on the type of projects you are specializing in. In this article we will zoom in on the factors you should consider when buying a drone for photogrammetry, LIDAR, thermal inspections purposes.

The drone market is evolving fast, so carefully consider all your options and opportunities before making a decision.

Drone

The first aspect to consider is the RTK/PPK capabilities of the drone. Especially in countries where NTRIP RTK corrections are available everywhere, it doesn’t make much sense anymore to invest in a drone without RTK capability. The quality of the work and the accuracy you need to achieve is so much easier and faster to get with an RTK drone. So let that be the first deciding factor in choosing the drone you’d like to buy if you consider it for professional use.

The second consideration should be: Do I need a fixed wing or a multirotor (rotary wing) drone? This is a question that you really need to answer for yourself. Basically if you only map small areas, it is not advisable to go for a fixed wing drone. The advantages for a fixed wing drone only really start to show when you have to regularly map areas of 100 hectares or more.

Also keep in mind that the camera in most fixed-wing drones points only straight down - this will prevent you from taking oblique images. We usually use oblique images for building and city mapping. Moreover, mapping facades for a single building is only possible with multirotor drones.

Always take into consideration legal aspects as well. If you have to maintain a visual line of sight, you might not even be allowed to map a 100 hectare area in one go. With a fixed wing, you need an area for take off and landing as well, which might not be available in the middle of a city. A hybrid model that allows vertical take off and landing (VTOL) can also solve this problem.

Furthermore you need to take into account the altitude you are allowed to fly at. If you are not allowed to fly at the altitude you need for a photogrammetry flight, but lower, you will just end up with a lot of extra pictures and a GSD which is over the top for your application, increasing processing time as well.

Of course, other factors are important:

  • Max flight time – you want the drone to fly as long as possible to cover more ground per battery

  • Max Transmission range – The longer the better, especially if you can fly Beyond visual line of sight

  • Terrain Follow features

  • Is the drone easy to transport and deploy?

  • Operating temperature range

  • Obstacle avoidance system is usually turned off during terrain mapping flights. It is useful only in close facade mapping projects.

  • Reliability of the drone - You don’t want to go to a far away location just to discover that your drone malfunctions, this is often the case with smaller manufacturers.

  • And last but not least, versatility: If you can have with one drone an easily interchangeable payload of Lidar/RGB/Thermal, and you need all 3, this might nudge you into the right direction.

  • (for drones that use 3rd party cameras) Camera power supply from the drone’s battery – Standard battery on big cameras like Sony A7 II lasts for around 500 photos

  • Max wind resistance – most drones can’t handle stronger wind than 10m/s

  • Quality of technical support

Drone camera (RGB - Visible Light)

When choosing a drone for mapping, you should be guided primarily by its integrated camera or camera payload capabilities.

First and foremost, the shutter type is very important.

For drone mapping the Global Shutter, also known as Mechanical Shutter, is the only recommended option. It captures light on the entire surface of the sensor immediately.

This is very important because the drone takes images while moving, so it needs a Global Shutter to capture undistorted images.

A Rolling Shutter, also known as Electronic Shutter is not recommended because it captures light line by line on the sensor surface. This can cause distortions that impact the alignment of the images.

Photogrammetry software like Pix4DMapper sometimes have an option that slightly improves the results of the Rolling Shutter, but after some comparisons between electronic and mechanical shutter on the same area at the same time the mechanical shutter is clearly superior.

Cameras like DJI X5, as well as those in the DJI Mavic series, Autel and Yuneec cameras have a Rolling Shutter. Those are not recommended cameras for mapping.

We use RGB cameras for most of our projects - Terrain mapping, Building mapping, Stockpile Volume Calculations, Power Line Mapping etc.

Below are some other things to look out for:

  • High Resolution - 20 megapixels or more

  • Sensor size - 1 inch sensor size or more (4/3, APS-C, Full Frame, Medium Format)

  • Short interval capture times - The faster the better - minimum 3 seconds

  • Camera gimbal quality

  • Dynamic Range

  • ISO noise levels

LIDAR

We use LIDAR scanners only for terrain mapping projects that are covered with dense vegetation.

Important features to look for:

  • Number of returns (echos) - the more returns the higher the chance of penetrating vegetation to the ground.

  • Built in RGB camera - to acquire RGB images during the LIDAR flight and color the point cloud

  • Weight - the lighter the sensor the more airtime per flight

  • Horizontal FOV/resolution

  • Vertical FOV/Resolution

  • Range - the longer the range, the higher you can fly and cover more area

  • Range accuracy

  • Scan Rate

  • Data Range

Thermal

We use Thermal cameras for solar panel inspections.

For those projects we require a radiometric thermal sensor with minimum resolution 640x512.

Additionally we require an irradiance sensor as a separate device.

Conclusion

As mentioned in the introduction of this article, since we don’t want to put one provider over another, we won’t give our preferred option here, we’ll just list some options, but feel free to ask us in private.

Drones and cameras that we have good experiences with:

  • DJI Phantom 4 RTK

  • DJI P1

  • Wingtra One

  • Quantum Systems Trinity F90+

  • Sensefly eBee series

  • Zenmuse H20T

  • Mavic 2 Enterprise Advanced with RTK add on

Drones and cameras that we aren’t convinced about:

  • DJI M210 RTK and M600 RTK - unreliable, a lot of hassle to sync the geotags with the images.

  • Drones with add-on third party PPK/RTK receivers (non-RTK / non-PPK native drones)

  • Mavic (except Mavic 2 Enterprise Advanced RTK)

  • Non - RTK / non-PPK drones

  • Rolling / Electronic shutter cameras

Safe flying!

Inflights Team

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