CODEWITHSUNDEEP
opencvimage-processingcomputer-visioncamera-calibration3d-reconstruction
Kamble Tanaji
Kamble Tanaji

Reputation: 497

How to calculate translation matrix?

I have 2D image data with respective camera location in latitude and longitude. I want to translate pixel co-ordinates to 3D world co-ordinates. I have access to intrinsic calibration parameters and Yaw, pitch and roll. Using Yaw, pitch and roll I can derive rotation matrix but I am not getting how to calculate translation matrix. As I am working on data set, I don't have access to camera physically. Please help me to derive translation matrix.

Upvotes: 2

Views: 375

Answers (1)

Francesco Callari
Francesco Callari

Reputation: 11825

Cannot be done at all if you don't have the elevation of the camera with respect to the ground (AGL or ASL) or another way to resolve the scale from the image (e.g. by identifying in the image an object of known size, for example a soccer stadium in an aerial image).

Assuming you can resolve the scale, the next question is how precisely you can (or want to) model the terrain. For a first approximation you can use a standard geodetical ellipsoid (e.g. WGS-84). For higher precision - especially for images shot from lower altitudes - you will need use a DTM and register it to the images. Either way, it is a standard back-projection problem: you compute the ray from the camera centre to the pixel, transform it into world coordinates, then intersect with the ellipsoid or DTM.

There are plenty of open source libraries to help you do that in various languages (e.g GeographicLib)

Edited to add suggestions:

Express your camera location in ECEF. Transform the ray from the camera in ECEF as well taking into account the camera rotation. You can both transformations using a library, e.g. nVector.

Then proceeed to intersect the ray with the ellipsoid, as explained in this answer.

Upvotes: 0

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