Hey, interesting question! I think using ground-based equipment to accurately measure the position of fast-moving drones in a large outdoor volume might be quite difficult. A pretty common way to do this indoors is to attach infrared retroreflectors to the object. You then have infrared cameras in different locations. Each camera viewpoint restricts the possible location of the marker to a cylinder along its view axis. Using two or more viewpoints, you can estimate the actual 3D position. Two problems for your application: 1) the infrared light from the sun will add a lot of noise to your measurements, 2) it is generally difficult to identify which marker is which. [1] is an example of an off-the-shelf system that works quite well though.
I think some onboard positioning system might work best for your application. kognate suggests using "inside out" tracking based on the features observed by a camera on the drone. A nice thing here is that most FPV drones are already transmitting realtime video. It would require significant computational power on the ground to localize drones from their camera feeds though. See [2] for some inspiration.
Another idea that may be possible is to use inertial sensor fusion algorithms using the data from the IMUs onboard the drones to find out their trajectory in real time. However this is quite a tricky business. The sensors would have to be characterized extremely well and be able to deal with the highly dynamic forces that would be felt by a racing drone. Probably would make sense as a standalone module that accepts 5V from the drone's power system and has its own IMU(s) and telemetry radios.
The sun gives off a heck of a lot of infrared, but the water in the atmosphere absorbs some frequency ranges. There's a pretty deep valley around 940 nm, and 940 nm illumination sources are cheap and readily available. Combined with a sufficiently narrow bandpass filter, sunlight may be less of a problem than you expect.
I think some onboard positioning system might work best for your application. kognate suggests using "inside out" tracking based on the features observed by a camera on the drone. A nice thing here is that most FPV drones are already transmitting realtime video. It would require significant computational power on the ground to localize drones from their camera feeds though. See [2] for some inspiration.
Another idea that may be possible is to use inertial sensor fusion algorithms using the data from the IMUs onboard the drones to find out their trajectory in real time. However this is quite a tricky business. The sensors would have to be characterized extremely well and be able to deal with the highly dynamic forces that would be felt by a racing drone. Probably would make sense as a standalone module that accepts 5V from the drone's power system and has its own IMU(s) and telemetry radios.
[1] https://optitrack.com/
[2] https://matthewearl.github.io/2021/03/06/mars2020-reproject/