The importance of Resection in Photogrammetry and its application

Resection is the procedure used in Photogrammetry software to determine the final position and aiming called the orientation of the photogrammetric camera when a picture is taken. Typically all the points that are seen and known in XYZ in the image are used to determine this orientation.
photogrammetry software

V-STARS uses the AutoStart or SuperStart operation to get the preliminary photogrammetric camera orientation. This Photogrammetry orientation is based on the AutoBar or any known coded targets.
For a strong resection, you should have at least twelve well-distributed points in each photograph. If your photogrammetry measurement does not have this many points, or they are not well distributed, it is recommendable to add points. Points that are added to strengthen the solution are called "fill-in" points. If the XYZ coordinates of the points on the object are known (we describe in Triangulation how this is done), we can compute the photogrammetric camera's orientation. It is important to realize that both the position and aiming direction of the photogrammetric camera are needed. It is not sufficient to know only the photogrammetry camera's position since the camera could be located in the same place but be aimed in any direction. Consequently, we must know the photogrammetric camera's position which is defined by three coordinates, and where it is aimed which is defined by three angles. Thus, although three values are needed to define a target point (three coordinates for its position)in photogrammetry, we need six values to define a picture (three coordinates for position, and three angles for the aiming direction).