CRITICAL REVIEW OF ORTHOPHOTO TECHNOLOGY fl AUTOMATIC MAP COMPILATION

Abstract

orthophotography is the result of a process by which it is attempted to convert to varying degrees of perfection, the central perspective of a conventional photograph into a parallel projection. Photographs obtained thus are known as orthophotographs and these will have no distortions due to tilt and relief and the scale will also be uniform. Horizontal distances measured on such photo. graphs would be correct regardless of the relief of the terrain. There was a long felt need for photographs on which data can be plotted or measured directly without the necessity of making adjustments for a varying .scale due to tilt and relief and the orthophotograph provided the answer to this. The device used for converting conventional pers.. pective photographs to the equivalent of orthographic photo. graphs is known as orthophotoscope. Chapter I introduces orthophotography and also deals with the solutions offered at an early state of the art. Chapter II gives a brief history of the orthopiQ oto.- scopes. Russel K. Bean's experimental orthophotoscope and the Engineered Prototype model have.been discussed fully bringing out clearly the improvements made in the latter instrument. The later models namely U-60 and T-64 have also been described fully. Chapter II also deals with the Gigas Zeiss Orthophotoprojector in which a conventional stereo.-plotting instrument (for example a C-8 planigraph) is used in conjunction with a separate GZl orthoprojector. Chapter III deals with the preparation of ortho-photo maps. The photo line,photo-tone process developed by the U.S. Army Map Service has been described and the details of the cartographic process used to obtain the orthophotomaps have been given. Chapter IV deals with the Automatic Map Compilation Systems,- The systems dealt with are 1) The Integrated Mapping System, 2) The Digital Automatic Map. Compilation System, 3) Automatic Stereomapping System and 4) The Automatic and the Universal Automatic Map Compilation Systems. The Chapter deals with these equipments in considerable detail, bringing out clearly their methods of operating, the accuracies obtained, their limitations and the scope of their future development, Chapter V deals with B-8 Stereomat (Stereomat 1V), in some detail. An account of the Stereotrigomat, which is yet another equipment for automatic map compilation, has also been included in this chapter. The chapter also deals with the orthophoto printer which is designed as an accessory to the Analytical Plotter system. Chapter VI gives the various applications of ortho-photography. -Applications to Geology have been discussed at quite some length. Applications of orthophotography for preparation of topographic maps, for urban planning and for revis ion of maps have also been discussed. Chapter VII gives a critical discussion of the limitations of orthophotography and Automatic Map Comp-ilation. The last Chapter gives a critical evaluation of the advantages and accuracies of orthophotography and Automatic- Map Compilation.. Systems. It also gives the conclusions drawn and brings out clearly the future of r these new techniques.