I will be attempting to scan a narrow canyon with my X8 wing soon. I am seeking input on the best method to obtain the best results. The canyon walls are at a very steep angle, varying between 30 and 50 degrees. Would it be best to image the canyon walls with the camera pointed straight down, or at the same angle as they are presented to the camera? Does anyone have any experience with this kind of situation?
I am concerned that if I point the camera straight down that only the ground in the center of the image will be in focus, and the ground above and below that area will be out of focus. Thoughts on that?
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You should get better results with a perpendicular shoot, which reduces obliqueness. For situations where you have objects extruding from the ground floor like houses or canyon walls, perspective also becomes something to consider. For example, if you're 5 meters from the house and looking straight down, you see the wall and the roof. At 0m from the house, you see nothing of the wall and the roof. 5 meters past the house you see the roof and less of the ground below. These situations can create some ambiguities for 3D reconstructions. It becomes more apparent when the object reaches half or more of the altitude the plane is flying at.
The focus situation really depends on how you configure the camera and what the depth of field is. Usually for these canon cameras when you focus at infinity, you get a depth of field of 5 meters in front of the camera to infinity. In other words, if you'lre not getting up to 5 meters from objects you should see them in focus. This is easily a situation you can test on the ground, to see from which distance objects close up become out of focus.
Thanks for the response, Gerard, and I see your point. I will do some testing as you suggest, to see what kind of results I can expect from a perpendicular orientation of the camera.