One of the important differences between a drone being a tool or a toy is the ability to produce accurate data. The principle way to produce accurate topo, point cloud, photographic data is to tie it to the ground through the use of aerial targets. The targets match the features in the collected data to known ground coordinates which rotate, scale, and elevate the data. The corrected data from the drone is now considered accurate. The measurements can be repeated by others at the site using those same target reference points.
Target How To
The task of putting down aerial targets can be considered tedious but it doesn’t have to be. Here are some recommendations and best practices when utilizing targets:
- Each manufacturer of commercial drones has a “How To” on what targets to use and where to put them.
- The preparation of the targets and the locations can be done well in advance of a flight. I use Google Earth to look over the boundary of the proposed area to be flown.
- You can create an area and determine distance between points while checking to see where the trees are. Placement of the targets will usually need to change over time though. The original targets are usually placed where they won’t be disturbed but sometimes are. Having a few extra targets in the bed of the pickup truck is always handy. They can be placed “On the Fly” and picked up after the flight. You will have to get them measured before you pick them up, usually as soon as you place them with the site survey GPS system, but not necessarily before the flight. You can add the coordinates for the targets in the processing software after the flight if the rover is tied up but you want to fly now. I know some who place a large “+” on the ground with inverted marking paint and a nail in the center. The point being to be prepared and have a few extra targets when needed. There may be a new low point in a pit or a high wall area that you want to be sure to account for. The target may only be there as a check point. Hover the mouse pointer over the target to see if the correct values were generated when compared to a direct measurement.
As companies get used to using a drone, they will expect the immediate gratification speed at which they gather information to become the norm. It would be unfortunate and a little costly if a flight crew had to go back to fly the site again, for the same information, with better target placement. So be a good “scout,” plan the area, be prepared with a few extra targets, and get it done right the first time.