BLOCK ADJUSTMENT USING CONTROL DISTANCES CONSTRAINT

Constraints are widely used in photogrammetric studies such as introduction of constraints on interior orientation parameters, exterior orientation paramours and object space coordinates of control points. The value of applied constraint lies in the ability to utilize the information to the greatest extends in reducing the magnitude of error propagations. This paper emphasises on deriving mathematical models based on using control distances constraint, which implies that each two points in the photogrammetric model should be constrained to a known distance, for simultaneous and self calibration block adjustments. Software's utilizing the derived mathematical models have been developed and tested using mathematical and actual photogrammetric data. The effects of block size, number and location of control distances, camera lens distortion and the random errors on bundle and self calibration block adjustments using the derived mathematical models and the conventional methods have been studied using simulated photogrammetric data. It was found that adding the control distances as constraint improves the accuracy of the adjustment.