Hello Everyone,
I am new to the UAV scene and have some questions about photo-mapping. I'm looking to use a GOPRO on a fixed wing UAV to do a research project. I want to take pictures, Geo-tag them, and overlay them into a map (2D or 3D). What is the best way to do this? What software and hardware would I need? Is there a way to have live feed to my PC from my GOPRO? My initial thought was to set GOPRO to time stamp each photo (take photos at a rate relative to speed), while I used Mission planner software to track coordinates of UAV. Once back on the ground I would use time stamped pics to overlay using GPS way-points on mission planner, but I'm not sure if there will be a huge offset, between time and place. I'm just looking for the easiest option, and I want to get the tools I need without spending a fortune. I'm learning on the fly (yes, pun intended) and would really appreciate any advice.
Thank you,
Josh
Replies
Regarding software, the first resource that opened my eyes to the possibilities of using aerial images and mapping/3D software was a tutorial I found at http://flightriot.com/post-processing-software/
Watch that and the related tutorials and you will get a better idea of the pre- and post-mission process. Also check out the balloon and kite mapping notes and blogs at http://publiclab.org which has a lot of overlap with UAV imaging and mapping as well as information about the Canon Hack Development Kit (CHDK - http://chdk.wikia.com) which allows you to program Canon cameras in ways that are useful for aerial surveys. DIYDrones and Ardupilot have similar tutorials which I've mentioned in another post.
On another topic, my GoPro 3+ Silver has wide, medium, and narrow image capture options. I don't know how narrow compares to most common SLR or point and shoot cameras, but from a quick look it seems that it doesn't have so much distortion that you would need special consideration for the images. That said, I think you'd be better off starting with a cheaper Canon camera.
My initial thought is to mount the camera on the bottom of the UAS so the lens is facing down, but I feel this could lead to damage upon landing. I see other drones with a forward facing lens, but think this would not be good for mapping because you are looking ahead of your location. Is there a way to use a forward facing lens without a ground reference point (I assume this is the only way unless you have a laser range finder)? Where does everyone else position their camera lens?
Josh, you should probably point your camera perpendicular to the plane you intend to image (image capture surface parallel to that plane). So if you are capturing a building, point horizontally, if the landscape, point down. This will allow you to capture the most information in the orientation you are interested in and it will make it easier for the software to find features in the images and stitch them together (assuming this is part of what you hope to do). UAVs with forward-facing cameras are probably focused on either FPV or capturing videos of the flight. With a camera in the same position but facing down, you can easily capture landscape images without worrying about damaging your camera when landing. If you mount the camera under the UAV body, you will probably need longer legs to provide the extra safety cushion.
I don´t know what are your purposes on photo-mapping, but keep in mind that the gopro lens is a wide angle, and even on high altitudes, the distortions are big and everything gets out of a scale;
just a friendly reminder ;)
Not only out of scale, but there are some BIG color shifts as you move from close perspective to distant perspective. I noticed that when launching my quad using a GoPro, the grass seemed a mix of green and brown but as I moved higher the green became much more yellow. I was using the Wide setting at the time so I don't know if this is a problem with Medium or Narrow but I suspect it is a side effect of white balance as the scenery changes. I haven't used my GoPro for mapping yet but I'll try to see how well VisualSFM can compensate for the fisheye effect. Like others have mentioned, Pix4D claims to be able to process GoPro images with distortion.
Thank you for the info everyone! I'm going to check into everyone's suggestions and see if I can make it happen.
Josh,
I was actually thinking of a similar question-although without the live feed. I imagine the resolution needed for 2d/3d mapping is hard to do over vhf/uhf. A low res live view and a high res camera on board archiving photos is probably the way to go.
My question pertains to the frequency at which you'll need to photograph images for your model. That's going to depend on altitude, speed, and focal length. Is there a calculator to determine what altitude I should be flying at to ensure I have enough overlapping images for a successful 3d model?
Good luck!
Jake
Jake, the tool that does just that is built into Mission Planner. There is a good tutorial at http://diydrones.com/profiles/blogs/how-to-plan-missions-for-aerial...
Finding the best percentage of overlap might come with a bit of trial and error, but the MP tools make it really easy to figure out how to automate the process for your selected camera, altitude, and flight path. See http://planner.ardupilot.com/wiki/common-3d-mapping/ for details about a minimum suggested overlap of 65%.
Hi,
Mission planner already has geotag software in it so there is no need to have a time stamp on the photos (press Ctrl+f when in mission planner to access the 'special' menu).
Just make sure the camera time is set to that of the GPS time (UTC) that you can see from mission planner (or just take a photo of the mission planner time to get the time stamp offset). Then you can use mission planner to geotag the photos afterwards (it will add the gps coordinates in the EXIF header of the image file).
There are various pieces of free software you can use to try and stitch all your images together, try micorosft ICE, AirphotSE or Visual SFM for starters (all free if non comercial). If you plan to add your data to something like a GIS system then you will need ground referance points to enable you to geo-reference the completed mosaic (either add them yourself or use prominate features).
S.
Sort of off topic but I'm curious has anyone ever tried Photo-Mapping using video? I have a gimbal-mounted (stabilized) Mobius Action Camera mounted to my Pixhawk quadcopter that I can point at the ground. It would be really cool to use a video recording to create a photo-map.
Maybe there is software that turns video into a set of images? Could the images be fed into Mission planner's geotag software and then used in a stitching program? I'm going to look into this.
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