A REVIEW OF METHODS OF TILT DETERMINATION INCLUDING 'EXPERIMENTAL INVESTIGATIONS ON A FEW CHOSEN GRAPHICAL METHODS

Abstract

This dissertation reviews the available methdds for the determination of tilt indicating the theory on which each method is based, the places of application, the accuracy and the versatility of various methods. The various analytical, mechanical and graphical tilt determination methods are presented in a concise form including their merits and demerits in chapter 4. The advantages and application of known tilt value is discussed in Chapter II. ■ A few graphical methods have been experimentally teated to study the effect of relief of terrain and the pattern of ground control point images on the photograph used for the solution of tilt on their accuracy. Keeping the tilt constant of 3°, the effect of reliefs of upto 1/6 of the flying height on the accuracy of tilt data have been studied. Again keeping the tilt constant at 3°1 and assuming a plane terrain, the effect of various patterns of control point positions on the tilt accuracy has also been studied. The Anderson's scale point method, Underwood's Modified Scale point; method and McNeil's Graphical Pyramid method are the methods considered for this experimental investigations. The results of these investigations are presented in Chapter V, The modern trends in the determination of tilt aro discussed in Chapter VI. In this chapter the recent developments such as stabilised mounts Sun Periscope etc are discussed. Only those methods of tilt determination which confine themselves to near vertical photographs are discussed here leaving aside the oblique photography case.