Hi there!
I collaborate with a drone team that uses a Phantom 4 (Standard) for research. For my work, I need to analyze their drone video and extract measurements of objects within their video.
The general methodology is that they record videos using their P4, and I take screenshots using VLC Media Player to obtain measurements. I'm comfortable with this methodology, and have accurate altitude (in m), focal length (3.61 mm) and sensor width (6.17 mm) information from this thread (Camera Intrinsic Matrix for DJI Phantom 4). I know that my collaborator is shooting in FHD, 1920 x 1080 px.
Using all of the information above, I can calculate my ground sampling distance, and scale my measured pixels to find the accurate measurement I need. Theoretically, my equation would be:
measurement = pixels_measured_in_screenshot x (altitude / focal length) x (sensor width / pixels)
aka
measurement = pixels_measured_in_screenshot x (altitude / 3.61 mm) x (6.17 mm / 1920 pixels)
The issue I'm finding is that some DJI drones do not utilize the entire sensor width when in video mode. There is a lot of documentation, as well just as visual documentation that when the camera changes from camera-mode to video-mode, there is a slight crop. This is due to the drone not utilizing the entire sensor, which means that my sensor width measurement will be incorrect. I have the corrected sensor width size for this slight crop for the Phantom 4 in 4K video mode, but not in FHD. I'm not sure if the FHD experiences this slight crop at all, as I am under the impression the drone does this to optimize video-writing speed, and I'm thinking maybe at FHD it doesn't need to do this anyway.
Sadly, I do not have the Phantom 4 standard in hand, only the P4P V2.0. So my question is, does anyone who has a Phantom 4 standard tell me if there is a video crop effect? If so, has anyone figured out the true sensor width used or the corrected pixel dimension or pixel width for it?
Thank you so much in advance! I greatly appreciate any help!!
I collaborate with a drone team that uses a Phantom 4 (Standard) for research. For my work, I need to analyze their drone video and extract measurements of objects within their video.
The general methodology is that they record videos using their P4, and I take screenshots using VLC Media Player to obtain measurements. I'm comfortable with this methodology, and have accurate altitude (in m), focal length (3.61 mm) and sensor width (6.17 mm) information from this thread (Camera Intrinsic Matrix for DJI Phantom 4). I know that my collaborator is shooting in FHD, 1920 x 1080 px.
Using all of the information above, I can calculate my ground sampling distance, and scale my measured pixels to find the accurate measurement I need. Theoretically, my equation would be:
measurement = pixels_measured_in_screenshot x (altitude / focal length) x (sensor width / pixels)
aka
measurement = pixels_measured_in_screenshot x (altitude / 3.61 mm) x (6.17 mm / 1920 pixels)
The issue I'm finding is that some DJI drones do not utilize the entire sensor width when in video mode. There is a lot of documentation, as well just as visual documentation that when the camera changes from camera-mode to video-mode, there is a slight crop. This is due to the drone not utilizing the entire sensor, which means that my sensor width measurement will be incorrect. I have the corrected sensor width size for this slight crop for the Phantom 4 in 4K video mode, but not in FHD. I'm not sure if the FHD experiences this slight crop at all, as I am under the impression the drone does this to optimize video-writing speed, and I'm thinking maybe at FHD it doesn't need to do this anyway.
Sadly, I do not have the Phantom 4 standard in hand, only the P4P V2.0. So my question is, does anyone who has a Phantom 4 standard tell me if there is a video crop effect? If so, has anyone figured out the true sensor width used or the corrected pixel dimension or pixel width for it?
Thank you so much in advance! I greatly appreciate any help!!
