stereo pairs

[iam_msy]

Hi,

I would like to know if it is possible to produce a 3D model with Correct Scale by using two still images at a time, taken from two cameras with fixed distance from each other? May I ask how would it be process by Zephyr Aerial and where would I input the fixed distance between the two cameras?

Thank you.

[Roberto]

Hi Iam,

You should add a control distance between the cameras (Measures dock on the right, then click on "Distance" under "Measurements") and then use the "scale model with control distances" to introduce a metric constraint. Currently, scaling between cameras is only rigid, and you can do it after the Structure from Motion phase.

[iam_msy]

Hi Roberto,

Thanks for the reply. When I tried to check that scale model with control distances, I think it is asking me to input the distance of the camera to the object which I do not know.

I think I need to explain more what I want to ask.

Please see the attached picture. I will be using two cameras with known distance to each other. I do not know the distance of the camera to the object. These cameras will take picture exactly at the same time. I will be downloading images from two cameras with different calibration values. My question is, how will I process the images in Zephyr if I would like them to have true scale? Will it be possible to have a 3d model that has a correct scale in this set-up?

[Roberto]

Sorry for the belated reply, we were busy with the release of new patch yesterday.

Yes, you can use the constraints of those cameras to get the metric scale. However, the only way is to import distances constraints between the cameras after the structure from motion phase with a rigid transformation. The relative motion cannot be currently introduced in the structure from motion directly. Constraints can be added only in the Pro and Aerial versions.

After the structure from motion phase, you have to click on "distances" from the measurements dock menu:



Set the constraint between two cameras:


Add more constraints (unfourtunately this has to be done manually, you don't need to add all the constraints, but more than 1 is certainly better)

Finally, click on scale model with control distances, add the metric distances between the stereo pairs and click ok to scale the world metrically.

[iam_msy]

Thanks Roberto!

By the way, did you attach some images? Could you please attach them again? I wasn't able to see them.

Regards,