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3 Most Common Mistakes in Farm Mapping with Drones

Precision agriculture means it’s now possible to create highly accurate drone maps. Drone operators can make maps with enough accuracy for a wide range of projects that can take your maps to an advanced level suitable for commercial purposes. A lot of people ask how to get the accuracy of crop maps? Of course, with the right tips and avoiding some mistakes in using drone technology, drone operators can increase the accuracy of their maps and create quality data. We have put top 3 common mistakes that we see with farm mapping with drones. These are mistakes we see all the time with clients or customers or some collaborators.

1.  Not enough overlap
The first mistake is not getting enough overlap in imagery. So, when you are flying with your drone and you have a camera on it and you're mapping, in general you want 80% frontlap when the drone is flying forward. And as it comes back around, you want around 75% sidelap or so. The tendency is that's a lot of overlap. And it can limit the area that you can map on a given fly or given battery or even within a day. So some folks want to reduce the amount of overlap. So that, it's getting 50-60% overlap in the imagery. And that can be one of the biggest reasons that a project will fail to process. And the reason for that has to do with the engines, the photogrammetry engines that are processing the imagery from the camera.

The solution is a higher overlap. Increasing the overlap for a flight is another way to create more matched points and greater accuracy. Overlap refers to the percentage of both sidelap and frontlap. Sidelap is the percentage of overlap between each leg of a flight, while frontlap refers to the percentage of overlap between one image and the next. Good default overlap is set at 60/70 in order to find a balance between accuracy and large image quantity. Many drone operators adjust the overlap depending on the needs of a particular project, striking a balance that creates the right amount of accuracy for the project’s outputs.

2. Inconsistent Lighting 

Problem number two that I see all the time is really has to do with lighting conditions. And so when we are mapping vegetation out in the field we care about how much light is coming down from the sky and bouncing off of the plants. And we use those differences in light to determine how healthy the plants are, and how productive they are. So if you're mapping under partly cloudy conditions, you're going to have variable light conditions. It's gonna mess things up. So the best practice is really to map under consistent lighting conditions, either consistently sunny or consistently cloudy. Strive to fly while the sun is highest in the sky and avoid weather patterns such as high winds and cloud cover. Under partly cloudy conditions, you might be flying with your drone and you're taking pictures and then a big cloud comes. This can artificially cause problems in your map and you might think that those problems are a problem with the plant themselves.

The high winds and rolling cloud cover should be avoided during mapping. Drones — especially lighter models — have difficulty staying steady during periods of high wind, which greatly affect image quality, which in turn affects a map’s overall accuracy. Where agriculture is involved, the movement of crops in the wind blurs imagery even more. While it’s possible, flying in winds higher than 10 mph can have a negative impact on the overall quality of your drone maps. So that's problem number two that I see, not flying under consistent lighting conditions.

To this end, drone operators should always try to plan missions in advance, know the weather and take steps to avoid mapping in poor conditions.

3. Not knowing the limitations of the camera

Problem number three that I see as really has to do with the cameras and not knowing the limitations of the cameras. So, a plant mapping camera that's designated for capturing plants. It's got different lenses with different filters for calculating very precise and wavelengths of light that are really specific to plants.

One of the simplest things that you can do to improve accuracy is to increase the resolution of your individual images, which can be achieved by using advanced cameras with a powerful sensor, like the ones found on DJI Mavic Pro and DJI Phantom Pro 4. Using a better camera results in much more high quality imagery with a higher resolution. For drone operators looking to upgrade further, some drone models also allow users to switch out cameras and sensors.

So, that's 3 general problems that we see in a using drone for mapping, namely not getting enough overlap fine, inconsistent lighting conditions, and not knowing the limitations of the camera.