255 For superficial leveling by the Netherlands Reclamation and Land Develop ment Service (Nederlandse Heide Maatschappij) an instrument Zeiss Ni 2 combined with portable wireless telephones was used. In this procedure a special extensible rod was used with which direct reading of elevation-figures in regard to N.A.P. (Normaal Amsterdams Peil), the Netherlands leveling datum, was possible. These elevation figures were written in the map in the terrain (17). The experiments, already mentioned in the previous Dutch report, with the latest photogrammetric instruments and methods for large-scale mapping were completed in the period under review. The "experiment Beltrum", just as recent experiments in Austria and Switzerland, has proved, to those who still doubted, that on economic grounds and also as far as accuracy is concerned, photogrammetry can be adopted as a normal method for detailed survey of most terrains (18 and rg). An important step for further application of photogrammetry in the Netherlands has been the establishment of a photogrammetric office of the Cadastral Service, to manufacture cadastral maps on the scales 11.000 and 12.000. A Zeiss stereoplanigraph C 8 has been chosen as plotting instru ment, this specially in connection with the possibility of plotting convergent photographs. Temporary, however, vertical photographs have been plotted because at the K.L.M., the airline company that makes the aerial photo graphs for the plotting services in the Netherlands, no convergent camera was available. Now such a camera is on hand. The first results of the new office are such that a favourable development may be expected. Other photogrammetric plotting services extended their instrumental outfit. Two new instruments, the Radialtriangulator of Prof. Roelofs, constructed by Wild (20) and the Kuipers lightspotprojector (2r), constructed by De Koningh, the Netherlands, were important contributions to the development of instruments. The theoretical research concerning the adjustment of aerial triangulation was continued by Prof. Roelofs. A practical example was published in (22). In (23) Ir. A. J. van der Weele describes an approximate method for this problem. In the field of international co-operation in photogrammetrical research it may be mentioned that since the establishment of the European Organi zation for Experimental Photogrammetry, the Netherlands take part in the work of this organization. There is a desire for co-operation in the map reproduction. On the initiative of the Cadastral Service in 1955 a sub-committee within the Netherlands Geodetic Commission has been installed in which are represented the large government services involved in the production of maps and also the Tech nical University of Delft. The task of this sub-committee is to organize co operation concerning experiments in the field of map reproduction in the different services. A working committee does the practical work. In (24) this committee has given a summary of the present state of the reproduction of maps in the Netherlands. Previously, investigations were made inciden tally concerning the deformation of plastic drawing bases and film (25). In (26) the methods of reproduction applied in the Cadastral Service in behalf of its own service, other services and private persons, are described in detail. The engraving process is used by some services only. Glass engraving has been tested successfully by the Hydrographic Office Royal Netherlands Navy in drawing Decca charts. However, the sea charts have such large dimensions that these are a check on the enduring application of this method. Literature 1. J. M. Tienstra: Theory of the adjustment of normally distributed ob servations. (N.V. Uitgeverij „Argus", Amsterdam 1956). 2. W. Baarda: Some remarks on the computation and adjustment of large systems of geodetic triangulation. (Bull. Géod. 1957, 20-49).

Digitale Tijdschriftenarchief Stichting De Hollandse Cirkel en Geo Informatie Nederland

Tijdschrift voor Kadaster en Landmeetkunde (KenL) | 1958 | | pagina 57