This is the second guest post from David Williams, founder of Northwest Drone Pros, in a series of posts on best practices for flying drones around trees. The first post covered “pre-flight tips“. David is an instructor in the free course, “Solar + Drones: Site Surveying and 3D Mapping Around Trees“.

In my previous post I offered six pre-flight tips for solar companies flying drones around trees. Now that we’ve covered before flight tips, let’s move to some recommendations for during flight.

Where to stand – When I arrive on a property the first things I’m looking at is my flight paths, and my footpaths. I want to maintain a visual line of site of my drone at all times so I need to know where to be to see it as I navigate it. If there is a gate that needs to be opened or I cant access one side of the property these are all things you want to know before you take off. In my experience its not the most comfortable feeling watching your drone go behind a 100 foot plus tree in POI mode (which I’ll discuss later) especially when there are most likely other trees behind it. Each property is of course unique but you want to put yourself in the best position to view your drone at all times even if it requires you to land to reposition yourself.

Generally you’ll be flying 2 flight paths which John will be discussing later, a detail and context (The context flight is the higher altitude flight path and is usually around 70 feet unless there are trees higher than that which is often the case here in the Pacific Northwest, and the detail flight is usually about 10 feet above the roof line) So you just want to map out your two flight plans in your head and know for the context flight that with the camera angle needed, the full point of interest in frame and 100 plus foot trees you’re going to need a decent diameter flight path.

I usually fly the context flight first because its at a higher altitude with a greater chance of collision because of altitude, temporary loss of line of site, wind and tall swaying trees. There are quite a bit of things to consider while the drone is airborne: camera angle, is the point of interest in frame, am I taking pictures with the right overlap, and sometimes battery life comes into play. So I’m able to relax a bit after the context flight is finished.

For the context flight or higher altitude flight the best position is wherever you can keep your drone in your line of sight. You’re most likely not going to be able to follow its flight path on foot because of the large diameter of the flight path and obstacles such as other properties or foliage that it will pass through. For the context flight the first thing you want to do is fly the drone over the tallest tree to determine what flight altitude to set. Once you’ve cleared the tallest obstacle in the area and set your flight altitude above that you’ll have peace of mind knowing you’re not going to hit anything when the drone is in point of interest mode. This is also helpful to determine what type of winds exist at that altitude.

For the Detail Flight or lower altitude flight If you can, stand directly beneath the drone or as close as possible. I find depth perception to be much more acute, you only need to worry about obstacles (in this case branches and leaves) on one plane whereas standing to the side and maneuvering the drone horizontally is harder to delineate both the vertical and horizontal planes. From the 2 images I provided you can tell how hard depth perception becomes when looking horizontally at multiple trees.  The same with the picture on the right, its near impossible to tell which branches are closer or farther.  By standing beneath the drone and using the sky to silhouette the trees its much easier to delineate the true edge of the trees profile. In the detail flight you wouldn’t be flying this close to a tree that would affect the solar array of the property your surveying because in that case you would need the whole tree in frame but often you’ll need to fly that close to other trees around the perimeter of the survey

This is the second in a series of solar plus drones guest posts.

Next, David will talk about the different kinds of trees that you’ll encounter in the field, including the unique challenges of each. This series is an adaptation of the “Solar + Drones” webinar developed in partnership with Scanifly.