What can cause an apparent change in pixel dimensions during aerial photogrammetry videos?

https://www.researchgate.net/post/What_can_cause_an_apparent_change_in_pixel_dimensions_during_aerial_photogrammetry_videos

Hello all,

Hello all,We are using the Inspire 2 drone/Zenmuse x7 camera to capture aerial videos of cetaceans. From these videos, we extract still images from which we then calculate the length and width of individual animals using a software that calculates morphometric measurements based on the pixel dimensions of the images, the lens focal length, and the height of the drone.

Hello all,We are using the Inspire 2 drone/Zenmuse x7 camera to capture aerial videos of cetaceans. From these videos, we extract still images from which we then calculate the length and width of individual animals using a software that calculates morphometric measurements based on the pixel dimensions of the images, the lens focal length, and the height of the drone.The videos are recorded at 5280x2160 resolution at an altitude of between 45-50 meters, using the DJI DL 50mm F2.8 LS ASPH lens, shutter speed 1/500, 29.97 fps. For some of our images, our pixel dimension appears to be 0.00445 mm/pixel, while in other images it is around 0.0034 mm/pixel (pixel dimensions calculated using a control object). This change in pixel dimension does not appear to be correlated with either the height or the tilt of the drone, and we have tried to camera in both auto-focus and manual-focus modes. We are not sure if this is an issue with the camera settings or a sign of a larger issue, but we would very much appreciate any suggestions as to what might be causing this problem!

Hello all,We are using the Inspire 2 drone/Zenmuse x7 camera to capture aerial videos of cetaceans. From these videos, we extract still images from which we then calculate the length and width of individual animals using a software that calculates morphometric measurements based on the pixel dimensions of the images, the lens focal length, and the height of the drone.The videos are recorded at 5280x2160 resolution at an altitude of between 45-50 meters, using the DJI DL 50mm F2.8 LS ASPH lens, shutter speed 1/500, 29.97 fps. For some of our images, our pixel dimension appears to be 0.00445 mm/pixel, while in other images it is around 0.0034 mm/pixel (pixel dimensions calculated using a control object). This change in pixel dimension does not appear to be correlated with either the height or the tilt of the drone, and we have tried to camera in both auto-focus and manual-focus modes. We are not sure if this is an issue with the camera settings or a sign of a larger issue, but we would very much appreciate any suggestions as to what might be causing this problem!Thank you all for your time.