First of all some background...
Having spent a good 2 years playing about with an Skywalker, Ursus and a Canon camera running CHDK, and designing my own uav, which actually flew recently ,I have come to the conclusion that flying wings may just be the best type of platform for short range aerial mapping tasks to create DEM, DSM models for GIS purposes.
The Skywalker was okay (but quite fragile, and now in pieces!), but I think it is too small to fit a roll gimbal on it. And I've found that if pictures are taken on a slight angle, it is very difficult to use software to tile them up nicely. this is my best effort, but far from perfect. The roads on the right do not line up as the camera must have been on a 45 degree angle when the picture was taken. (click for larger resolution) - It was taken using an ixus80 attached to an URSUS Airframe
Realizing that I need to use an airframe that can accommodate a stabilized roll gimbal, i started to design and build my own twin boom design. It took 6 months from initial design, to first test flight. It has a wingspan of 2.4m - AUW of 5kg, and a flight duration of around 30 minutes with 2 x 5000mah packs. However it needs a heck of a lot of room to take off and land, something i don't have in the areas i need to take photos.
Picture of twin boom plane...
What are peoples experiences with using flying wings for this reason? I have the following types of flying wings, and wondering which one is the best to begin with?
I have been using the 60" wing to test the APM2 and 3dr radios. And was using the URSUS (now in pieces after a nasty crash!) as a test platform to practice with the Canon CHDK Kit.
Here's a few pictures of the wing and camera....(click images for larger version.)
My question is how straight forward do you think it is to fit a roll stabilized gimbal to any of the above airframes?
So thought I'd add version 1, the simplest way to get the camera onto the wing. No roll axis, but a good way to test where the camera needs to go for the COG. Basically, add a detachable EPP underside with cutout for camera, and use hook and loop / Nylon screws to attach to plane.
Here is a drawing....
I just cut a hole in the wing and push the camera in from the top. Its not critical that the camera is on the CG. I find using the images from one direction only with a lawnmower pattern works best.
Useful info, cheers Gary, The only issue, is that the camera is going to have to go a fair way out onto one of the wings. As the central portion of the wings has holes for the batteries, ubec, 3dr, apm, esc, rc and motor.
The closest area would be passed one of the servos, would that be okay? I think it'll probably add to much weight making the wing unstable in roll.
It's been a while since i flew this plane, and i am now trying to work out the CG.using the online CG calculator. What's your take on Gimbals, are they necessary to get decent pictures to be used for aerial mapping?
No gimbals don't add enough value vs the hassle. What is most important is light when you are taking the shots! Lots of light, lots of perfect pics. You should have loads of room in the X8 for a Canon ;-) In fact in that you could have one vertical and one with and overlapping image slightly oblique and that would help making more dense point clouds.
I've just used a calculator to find out the CG - I've entered all units in mm. It gives the CG @ 247.18mm. I have found different sources of information saying CG is measured from wing LE or TE, but this calculator does not say. Is it fair to make an assumption that the CG is being calculated from the LE?
The point about using two cameras, Now that is interesting and something i definitely need to think about.
In the image above, Microsoft ICE was unable to stitch the photos together due to the angle the photos were taken, the road is not joined up on the RHS of the photo. If there was a bit of wind the camera and plane could be rolling around a fair bit making photo runs quite difficult to get in focus. I have not tried putting a camera on a wing before. So i'll go with the no gimbal approach, and see how i get on with that.
the other reason behind wanting to stick the EPP block onto the underside of the wing, is that i find launching the wing quite difficult, therefore i will cut some finger holes out AFT of the camera position, similar to the X8 finger holes.
I am still contemplating what power system to use for the X8. I have been recommended the ax2820 from BevRc, but it's sold out, I only really need the motor, got the rest of the bits. I've just recently started using eCalc. decisions decisions!
Have you tried photosynth? I find it much better than MICE, you can extract the point cloud as well.
Bendy point clouds mind, this one from a wing.
This one, hex/wing with oblique stuff so much better point cloud
Not played with it much recently, I have been too busy with sUAS News but I am sure its better these days.
I did try Photosynth a while back, but that generates weird clickable images, couldn't get it to generate a nice single large image, stitched together. I thought that was what Microsoft ICE was for. I even sent the images to Dronemapper, and Pierre ran them through their software for free for me as a test. But said the photos were all taken from different angles. therefore that's why I thought a gimbal was needed.
I'll see how i get on this coming weekend, re: lots of light, I think i set shutter speed to 1/800 or 1/1000 and always got crisp shots in bright sunlight. However on cloudy days i found it difficult to get crisp bright photos. It's been a while since i played with the CHDK, i seem to remember that iso 400 (max), high shutter speed, and infinity focus are the 3 main things necessary to do good photos.
Due to limitations of current component placement, I have to stick the camera underneath the wing, until i can cut a new wing out. Heres the plan.. Cut polystyrene block out in the shape outlined below, and cut a large hole which will be foam lined to absorb motor vibration.
You have an X8 and that is good enough reason on its own, but I was just wondering is there a reason you are using a 60" wing?
The reason I ask is that most of the commercially available systems are around the 1m wingsan and don't have a gimbal system, they easily meet your current 30mins flight time etc.
gatewing x100 http://www.gatewing.com/X100
sensefly swinglet and ebee http://www.sensefly.com/
I havent really checked out the sensefly ebee, fairly new release, but I have demo'd the smartplane, very well thought out, nice kit.
You may be just as well off with a smaller plane, an X5 is cheap enough for a starter, at least I would rather cut into one of those to experiment with before I cut into my X8, and theres quite a bit of room inside for a gimble if you wanted to add one.
If you watch any video of them they all fly pretty fast, maybe the speed and smaller size means the photos are not as affected as much??
Fast shutter speed and good light are going to be your best bet for better pics tho.
Hi Pete, cheers for the links, again very useful information. The only reason i was going with the 60" wing is so that I can get a decent flight time, and i've got a wing already setup with APM2. I will possilby look into using the 48" zagi instead. However i have found that i need a gimbal to get vertical photos to stitch photos. based on my example above which shows that the software can't stitch photos when taken at an angle. noticed the Gatewing plane has a gimbal in it, as does the pteryx.
Hopefully will have some sunny weather tomorrow!