Aerial Triangulation in Photogrammetry Software is the principle used by both photogrammetry and theodolites to produce 3-dimensional point measurements. By mathematically intersecting converging lines in space, the precise location of the point can be determined. However, unlike theodolites, photogrammetry can measure multiple points at a time with virtually no limit on the number of simultaneously triangulated points.
In the case of theodolites, two angles are measured to generate a line from each theodolite. In the case of photogrammetry, it is the two dimensional (x, y) location of the target on the image that is measured to produce this line. By taking pictures from at least two different locations and measuring the same target in each picture a "line of sight" is developed from each camera location to the target. If the photogrammetric camera location and aiming direction are known (we describe how this is done in Resection), the lines can be mathematically intersected to produce the XYZ coordinates of each targeted point in Photogrammetry.
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