Photogrammetry & Aerial Surveying

Photogrammetry, so what is it? What if I told you that its origins date back to the grand old master himself, Leonardo Da Vinci and also Albrecht Duerer, in the 1400 and 1500’s. Perhaps not in the same sense as we use the term today, but they were the first to use mathematical science to determine perspective within their drawings. From this developed the use of mathematical principles to determine the co ordinates of a point in 3d space from two or more images. Imagine that but using modern digital cameras and the power of computers to match every pixel from two different photographs (pairs) and then using hundreds of photos over hectares of terrain. So how does it work, initially I just thought it was voodoo magic, but apparently not, and when I researched it, its not so difficult to understand. Taking a photograph is the process of capturing the 3d world and applying it to a 2d canvas. Photogrammetry , in its simplest form, reverses this process and gives us the 3rd dimension back. Take us, humans, actually take most living things on this planet that have eyes, but just the ones with two for now!, If we only possessed one, depth perception would be neigh on impossible, but two, side by side, gives us the ability to judge depth. This is not so dissimilar to the way a camera, with one lens can be used while mounted on an aerial system. While moving forward it take a series of photographs, the second image overlapping the first, the third overlapping the second, etc, using pairs of these images, two eyes, and knowing the focal distance and sensor size, imaginary (or computed) rays can be formed back to the camera to produce a line of sight, with orientation and position, to a specific point, in this case a line for every pixel, triangulation is then used on both images, where the rays for matching pixels intersect, that point gives us depth.

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