7.17 The large-scale aerial mapping programme continued to run down with the virtual completion of the extra mapping contract for selected areas above the 600 feet contour line. However, with the installation of the new R.C.10 air survey camera in March 1972 in the new 'Islander' aircraft of the R.H.K.A.A.F. it is hoped that a new mapping contract will be let in the coming year.
7.18 The existing main triangulation framework was broken down using an accurate geodetic theodolite to provide a system of precise minor control in connection with the Mass Transit system proposals. This control was used to provide very accurate surveys in areas where development could conflict with proposals of the Mass Transit scheme.
7.19 On the Cartographic side the work was divided between the drawing of title plans, the drawing of large-scale maps following field revision and the production and revision of small-scale maps. Good progress was made with most aspects of the work and this is expected to continue in the coming year.
Control Survey
7.20 The number of control surveys in the urban areas increased considerably this year, following closely on the completion of the accurate traversing required along the routes of the Mass Transit scheme. The use of Electronic-Distance Measuring Equipment has enabled this work to be carried out quickly, and to a higher precision than had been possible before. Permanent control points have been established at rooftop level near the proposed Mass Transit alignment, being termed Route Reference Points (R.R.O.s).
7.21 Break-down to ground level traverses has been provided, giving priority to those areas where surveys have been required for lots that could be affected by Mass Transit proposals. Close co-ordination has been necessary throughout this work between the Senior Land Surveyor (Control) and the staff of the Mass Transit Branch of Highways Office.
7.22 Bench Mark levelling continued this year on Hong Kong Island with the revision of certain areas where new points were established and existing Bench Marks were brought up to the standard of accuracy set by the precise relevelling commenced during the previous year. Areas on Lantau Island, at Tai O and Silvermine Bay were provided with a series of Bench Mark stations.
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