Close Range Photogrammetry

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Close Range Photogrammetry is the reconstruction of object simultaneously from several images. After that different perspective are taken from those taken images. And the best possible perspective is used to ensure suitable geometry of intersecting rays. Close Range Photogrammetry is reconstructed from rays where the free stationed images are in objects space. In Close Range Photogrammetry the factors that are responsible for the estimation of some common processes called ‘bundle of adjustment’ are-

Object coordinate interior orientation of the camera exterior orientation of the camera

As we all know that photogrammetry is the best used measurement tool, close range photogrammetry is also gaining its importance with a fast pace. Some fields where this techniques are used very frequently are –

geometrical calibrations deformation analysis crucial dimension quality control

Some other common calculations, where Close Range Photogrammetry is often used are as follows :

stripe length diameters and separation between columns along other dimension dimensional information about lane widths analysis of accidental photogrammetry

Close Range Photogrammetric Techniques offer measurement of large objects having a diameter from 1 to 300 meters. In Close Range Photogrammetry images are generally taken from a lifting or scaffolding platform. Under this constraint or

circumstances there are two important points regarding camera that should be taken care of. These are –

interior orientation of the camera stability of the camera

In Close Range Photogrammetry mainly there are four types of perspective images. These are _

One point perspective imagery – in this type all lines perpendicular to the image plane converge to a common point, generally principal point on the ray of camera. Two point perspective imagery – here camera angle is rotated at an angle which must be more than 6 degree. Three point perspective imagery – here all horizontal lines converge to the vanishing point to the left and right. true or direct scale perspective imagery – here the camera plane is is parallel to a common plane of object. This common plane may be a side of a vehicle or may be a wall.

Elements of Close Range Photogrammetry are –

2D Conformal Projection: it is divided into

Similarity transform: rigid Euclidean transform with scaling, between the primary (X,Y,Z) and the secondary (x,y,z) coordinate systems. Seven parameters describe the transform:3 translation steps (orthogonal), 3 rotation angles and one scaling parameter. This transform is called conformal, because it does not change the shape of an object (only its relative position and size).

General 2D Transformation :

In the image plane, non-uniform scaling in the X and Y directions as well non-orthogonal rotations, together with a translation of the origin define an affine 2D transform. More general 2D transform are expressed using polynomials of varying degrees.

There are some other factors also which influences the the Close Range Photogrammetry. These are –

single camera geometry geometry of two cameras multi station convergent geometry

Thus it can be concluded that though Close Range Photogrammetry is a very complected technique which is very useful for various purposes. With the technological development in can be said that more improved method will come to solve more complicated techniques.