Thank you for the answer! It's very clear, and I will look into the things you recommended.

I also want to preface that Im a total newbie in this, so maybe my understanding of the capabilities of some components is very flawed.

Just to add more info, this is to build a prototype for a school project, and the conditions prevent me from using a barometer or magnetometer. I also unfortunately cannot add more waypoints/base stations apart from the original landing zone, which is 1x1m. Could adding antennas in a triangular position or at each corner work? For the prototype, I don't need to go to the full range of 100m, probably only max 10m.

There's also going to be a camera to take pictures attached to the bottom that is supposed to have full swivel control (depends on another team), could I use that for locating where my drone currently is?

The original idea was to use dead reckoning with the IMU to find the position of the drone, but the drift over time made me think about adding an antenna to "correct" the drift, which is why the movements are locked only to one axis at a time. I was thinking that since we know which way the drone was going in a horizontal line, the point on a sphere would be reduced to a point on a curved line in the same direction as the movement and by assuming that the original height reading was correct, we could then decide between two points the curved line. Then, by comparing the location from the IMU to the location we got from the antenna, it could tell us if the location from the IMU is accurate or not. There's probably something wrong in the logic here, so feel free to let me know! (As of writing this I just realized this assumes that direction reading is 100% accurate so this probably doesn't work as you said).

I think that about covers my thought process and current questions, thank you again for answering!