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Dual camera capture for better resolution. Matrice 210?

Is it possible to capture survey images with 2 cameras at the same time?

My thinking is this: we have a wide angle camera (X4S, 24mm equiv) capturing at 70% overlap, PLUS a longer focal length (X5S with 50mm equiv) capturing with about 30% overlap. The longer lens will give much higher spatial resolution, and the wider lens will ensure all areas are mapped.

My hope is that we can effectively use the wider images to help the longer images stitch together more reliably, but the final product (a 2D orthomosaic) would have the much higher resolution of the longer FL, compared with using the wider lens on its own.

Can Pix4D facilitate the capture sequence for both cameras (I believe they sync together on the UAV anyway)?

Is there any reason the above plan would not work?

Hi Ross, 

I would recommend you to have a look at this DJI M210/M210(RTK) Dual Gimbal Support community thread to get the latest news about Dual Gimbal Support.

However, Pix4Dcapture supports DJI’s single downward-facing gimbal so you can consider flying two separate missions with your X4S and X5S cameras.

For an optimized reconstruction, we advise that you keep a constant ground sampling distance between overlapping images. Therefore, we do not recommend that you have several GSDs for one project, which would be the case for the mission you described because the X4S and X5S have different sensors and focal lengths. It may affect the reconstruction or even fail.

I understand the theory behind your proposal, considering that the GSD you will capture with your X5S will be much more detailed than the X4S’ GSD. However, we must also consider the amount of image overlap that you will capture because I anticipate that Pix4D’s image processing engine will not calibrate the X5S images due to the significant difference in GSD between the X4S and X5S, which may yield significantly different distributions of Automatic Keypoints in overlapping X4S and X5S images.

Nevertheless, please let us know the outcome of your project if you fly a mission that matches your original description with another third-party application.

 

best,

Thanks for the response. Would it be possible to have pix4D handle the flight, and manually initiate capture some other way? Would I need to initiate capture on the RC, or could I switch to DJI Go in flight, with Pix4D still managing the programmed flight?

Maybe the above is possible with a dual controller setup? One controller running Pix4D capture for flight control, and the other running DJI Go for capture? Is that possible?

Hi Ross,

I think that Andrew’s last comment on DJI M210/M210(RTK) Dual Gimbal Support is answering your questions above:

https://community.pix4d.com/t/5886/comments/360000562423

To sum up there is no easy workaround that can be done for the moment and it is not guaranteed that it will work. Don’t hesitate to feedback us if you take the opportunity to test the dual downward-facing gimbal anyway.

Ross, the easiest solution that I do for 1 mm modeling and mapping is fly everything at a high resolution.  If your need is to get high detail and relative accuracy then why bother with a camera that can’t provide the necessary GSD?  Now I do see some benefit by flying RGB and LiDAR at the same time but I just haven’t heard of a project needing 2 RGB cameras for a “bad” and “good” resolution.

@Adam, my reasoning for getting a “bad” image set is to allow for a lower image overlap on the “good” image set, which means we can cover the same area in less flight time (or a larger area in the same flight time) without sacrificing resolution. The “good” image set would have an image overlap of ~28% which is not enough to reliably assemble the mosaic, so the “bad” image set (with ~70% overlap) would play the role of helping to align them. Every “good” image will overlap 100% with one “bad” image, and since that “bad” image has plenty of information to accurately align within the larger mosaic, the “good” image should be able to reliably align as well*. The benefit would effectively be the ability to capture mosaics with a much lower overlap setting than is possible with a single camera, which is a very worthwhile goal in my case.

@Gael yes, I think you’re right. The limitation on the aircraft not connecting at all to any other software may completely rule out this idea, at least with Pix4D. Thank you.

 

*I’ve flewn surveys over the same area of land at different heights with a single camera, and used both image sets to create a single mosaic before, my thinking is that this method would be similar, but with a single flight.

I understand your question but Pix4D isn’t going to like different camera models in the same project with such a low overlap. The behind the scenes algorithms will just break for what you want, but that is just my experience and I don’t know the actual code.

Flying different heights but with the same Pix4D camera model is easy but you want to mesh an orthomosaic from 2 totally different projects…and of course the 30% overlap will make a worthless project.

While I see your point on flight time and picture volume, I am 99.999% sure it is impossible with Pix4D and all the others I have tried probably won’t do it either.

@Adam, fair enough. I believe PhotoScan Pro can handle the processing (you can create and apply separate camera calibrations within the same project, and merge image sets from each of those cameras, using the appropriate calibration profile). I haven’t tried this yet, but I’ve read that it can work well.

At the moment, my stumbling block is on the capture side; I can’t find a solution (yet) to allow for both cameras to trigger during a mission.

My M600 triggers the camera independently and could certainly run two cameras with a custom gimbal setup…and I use Pix4Dcapture.

@Adam, could you elaborate a little? What do you mean by “triggers the camera indepentantly”? Is this triggering system different than the M210?

I know that it’s easy enough to run 2 cameras, unfortunately Pix4D (and others) can’t actually *trigger* both mounted cameras. Searching around, plenty of people are coming up against this problem when trying to capture visible (eg: X5S) and thermal (XT) simultaneously. Apparently only one of the connected cameras actually triggers. Even DJI’s own GS Pro software lists support for dual camera capture “Only for Manual Flight”.

Ross, with the custom camera option of the M600 on iOS Pix4Dcapture, it assumes an external trigger so Pix4Dcapture doesn’t actually trigger the camera.  In this setup Pix4Dcapture just flies the drone and doesn’t take pictures so you need a camera setup that works independently.

It is beyond the “off-the-shelf” setup but well worth the effort to capture a mapping project with a zoomed in 42MP camera.  And with a custom Pix4D processing rig then I can run single projects just over 200 gigapixels (5,000 of the 42MP images).  Of course this high detail work isn’t done on a Phantom and laptop budget :slight_smile: