Need help with altitude measurement

[david88eve]

Hi, I was hoping that you guys could help me out with something.
I've built my own hexacopter, and am using crius aio 1.1 as my flightcontroller.

What I need, is a "device" or setup that shows me the exact altitude of my copter in relation to here I stawnd.
It has to be more precise than the built-in sensor (barometer) on the flightcontroller, but does not necessarily need to be connected to the fc.
I was thinking maybe a two-part device, one on the ground, and one on the copter, but I have no idea what that would be.

All ideas and suggestions is much appreciated.

David

 

[jpanhalt]

By "exact" altitude do you mean ± cm, meters, or what?

Second, meeting the specification that the height/altitude must be relative to where you are standing and not relative to what the helicopter is over might be difficult to meet, depending on the degree of precision that you need. You could use a laser distance measuring device to determine height over the terrain where the helicopter is. Even ultrasound might work too, if high precision is not needed.

John

 

[david88eve]

Hi!
It would certaintly make it easier if it could be related to the copter.

The reason I asked about it being relative to where I'm standing, is because im going to measure over water, and I figured a laser would hit the water, reflect, and give me bad results, but I dont know.

So what I need, is a solution that allows me to see my copters height from ground, fly over the water, take a picture at 100 meters, and unfortunately, I need it to be in the cm precision range.

Thanks for helping me with this

 

[jpanhalt]

To get 1 part in 10,000 precision height over water will be quite difficult. Can you even control the helicopter that precisely, not only in altitude but in pitch and roll? You will need a gyro-stabilized device to avoid errors introduced by a little tilt.

Laser will penetrate the water surface to varying degrees depending on clarity and waves. But, if you can float something on the water for your target, it might work. Sound is out of the question.

John

 

[david88eve]

I have mounted a gyro stabilized gimbal underneath the copter, but I'll need to modify it slightly to get the precision I need. It shouldn't be a big problem keeping the copter stable at 100m

lets say I have a platform on the water, and can keep the copter stable. What kind of electronics do I need to get the altitude readings delivered to me on ground?

As I said before, it doesn't have to be wired with the flightcontroller.

Again, really appreciate your help.

 

[jpanhalt]

I would hack one of the now very common laser distance measuring devices. If the device has any sort of data logging output, as I expect something with the precision you need might have, then it is just a matter of doing a serial link between that and your ground station. There are many RF modules available that will do that. XBee devices are easy to work with (https://www.digi.com/technology/rf-articles/wireless-zigbee)

John


John

 

[david88eve]

Thanks for that info, will definitely check it out. I will update this post as I progress.

David

 

[jpanhalt]

If it is just a one time deal, you might consider using a video camera focused on the laser readout with a downlink. Those downlinks are becoming quite common. You can search on Predator drone or for hobbyists, First Person View (FPV).

John

 

[david88eve]

I have a fpv solution with a 5.8ghz transmitter and receiver. Maybe there's a way to show altitude info on my ground monitor? Or else I could get one more camera.
Would be awesome if the altitude info could be integrated with the video, but that's probably not possible.