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Difference between nadir for drones vs crewed flights

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Civil Air Patrol just adopted a new website to upload aerial photography to FEMA. The name of the website is Disasters Geoplatform Imagery Data Management Portal by ESRI. One procedure made me wonder about how drones work.

When we classify the photos, we are instructed to classify nadir photos from sUAS as nadir, and all photos from fixed-wing crewed aircraft taken with hand-held Nikon cameras as oblique. We are to do this even if we have made our best effort to take nadir photos with the hand-held cameras.

Is there something about drones that help them do a better job of keeping the optical axis of the camera pointed straight down? These photos would be before any post-processing to stitch them together.

I have several crewed aircraft aerial photo flights under my belt, but am just getting started with drones.

Posted : November 5, 2022 5:32 pm
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John Putnam
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For photogrammetry purposes, nadir photos need to be pretty close to vertical.  Without my references material handy I cannot give you a proper spec but tight enough that aerial mapping camera operators used to adjust the camera mounts in real time to maintain the correct alignment.

Drones have IMUs to maintain the nadir alignment of the camera.  While you can use oblique photography (anything other than nadir) it becomes a bit more complicated in terms of mapping.  Obliques are primarily used for interpretation on unless you have some specific information relating to the orientation of the camera.

Posted : November 6, 2022 5:45 am
Rover83 and ashton reacted
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we had IMUs on everything we flew fixed wing at Sanborn. Without them it would be a complete $#!tshow.

Posted : November 6, 2022 7:40 am

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@jitterboogie oh come on now. You can solve for pitch an yawl also. Nadir is just a southern slang for tater lol you can bake them fry them boil or mash them. Even eat them raw or yawl lol. Tis why a lot of people lay survey data over satellite imagery and say it off. Sometimes its the angle and a trained eye can make a pretty good guess of where it would line up at if it was at nadir.

Posted : November 8, 2022 5:45 pm
Jitterboogie reacted