Digital large scale restitution and map compilation

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Abstract

For the effective performance of its work, the Rijkswaterstaat, which has a staff of about 12.000, consists of 25 Directorates with different duties. One of them is the Meetkundige Dienst (Survey Department) with a staff of about 500, which is charged with the geodetic support of the Rijkswaterstaat. Part of this support is the preparation of large-scale maps for various purposes. These are mainly prepared photogrammetrically, for which purpose the Survey Department currently has at its disposal about 35 stereoplotters. At the end of the 'sixties the Survey Department had 12 stereoplotters which were worked on a two-shift system. This capacity was insufficient to satisfy the demand for maps. One of the possibilities for increasing the production capacity appeared to be digital mapping. A system was introduced based on digital recording direct to paper tape at the photogrammetric instrument. lts subsequent gradual development is described in this publication, up to and including the introduction of an interactive graphical system. The HRD-I Laser Display with its 70 x 100 cm screen forms an essential part of this system. In addition to a prescription of the hardware configuration, detailed information is given about the software and operational procedures. The method of digital map compilation that has been devised has the following characteristics: - information is collected at about 20 photogrammetric plotting instruments simultaneosly and there is one central processing system for updating, etc.; - the operators of the photogrammetric instruments digitize 'blind', i.e. they have no displays available to them that register the progress of the digitizing; - each photogrammetric instrument being used digitally has its own tape punch for recording the information; - when digitizing, each feature is provided with a code which denotes its drafting symbol rather than its function; the digital information is fed off-Iine to the centraI processing system; in the design of the system, the compilation of maps was the main aim and not the creation of a topographic data bank; the design is such that information from other sources can be processed, such as that obtained in the field with electronic tacheometers, or from existing maps with the aid of digitizing tabels.