PIX4Dfields – How to calibrate drone cameras for mapping crops (in-field tutorial)
Today. One thing to note is that each one of these are different and each one of these calibration panels typically has a sample target it. Normally it could have a compass or level bubble, but it has these qr codes that convey some sort of information back to our system that automatically enters the numbers of the calibration. These targets are typically calibrated in a lab somewhere and they know the specific reflectance of this target so when sunlight hits it and reflects, we know exactly what that color is. Color does change every day from from morning to night, a lot of people dont notice. This with their eyes, i particularly colorblind so im really not noticing this type of thing but light shifts. You know, as it goes through the atmosphere so um you want to take care of this. This sample oftentimes theyre covered, and so we have this sample here. That has a cover on it. We dont want to smudge this target or get it dirty. We want to not get grease marks or anything. We want to preserve it as it was as it came. We dont want to leave it out in the sunlight for long periods of time where it could warp or fade. So when were done, we want to close it up and put it away if we can. So the method of calibration that we use at pix4d is very simple. You know you find a nice open area away from trees away from vehicles.
Typically, this truck is black, so it might be okay, but if it was a red truck and it reflected lots of red light, that might be a problem so away from everything that might bias the color you dont want to wear red shoes or bright shiny shoes Or bright pants or a shirt or something that day when youre, calibrating okay youre going to lay your target out as flat as you can. You want to orient it north and you want to just position it so that the sun can hit it and reflect back into the camera during the detection. One example i want to use is this phantom, because people have trouble with this one. I understand that uh, the camera likes to orient itself up when it when you get ready to take off, and so what people have been doing is they want to tip the cam? The camera like this to take a picture now this has got a problem with it, and i just want to point out real quick that the radiance sensor, the light sun sensor here, thats taking a sample of light, is not pointed at the sun. This needs to be pointed straight up and level in this camera. Youll have to use the remote to make it turn straight down and then youll have to use the ipad to capture the photo. When you do this, and you want to center it over the top, be careful not to cast a shadow over your target, this would be a badge, a bad picture.
When youre doing something like this, because youre shadowing your target and your qr code, you want to stay away from it. You want to stay up above it, and then you want to also be out of the light thats coming down. I dont want to shadow my light sensor and then i might be okay underneath, but i might be shadowing my light sensor on top. I want to have my my front to the to this sun and i want to capture it such like. This, fixed wings, are maybe a little bit harder. They take a little bit more talent, but you know on certain days you can figure out how to do it. Just about right like that. Okay and then you click, a button. Itll normally trigger after so many seconds, and then your calibration is done. Some people like to calibrate their photos before and after theres, a good reason for this. Sometimes when you get out of an air conditioned vehicle at the very beginning, and then when you come out into a humid air youre going to have fogging on your lenses. So double check their lenses, make sure that theyre not fogged underneath and make sure that theyre ready to take a picture. Otherwise, if you take one at the end, its probably gon na save you in case you took a bad calibration photo at the beginning, so in real shortly ive covered how to calibrate your camera, the many different targets that we can use in pix4d fields.