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found impracticable to utilize it in the preparation of the new maps and as all filling in had been done by plane table it was not possible to replot the survey.
Here again the mistake of variety of scales was repeated, those employed being different from any of the plans previously produced. A considerable area was plotted on a scale of 16″ -1 mile (1″-330 feet), but, as this was found to be too small to be applicable to many parts, a scale of 32′′-1 mile (1′′-165 feet) was adopted for the remainder.
After full consideration of the matter, it was decided that the new Ordnance Maps should be plotted on scales of 200 feet and 50 feet 1 inch, the latter being only used for populous areas or where early development of the country might be expected.
The Indian Survey meridian was accepted temporarily and, when the triangulation was carried through from a base at Tai Po which had already been co-ordinated, its bearing was found to disagree by only 3″. It has therefore been decided to accept the original meridian.
In the new triangulation, as already mentioned, a base was laid out at Tai Po measuring 2,168.786 feet and this was extended by a series of well-conditioned triangles, 15 in number, to Ngau Shi Wan where another base 2,271.525 feet in length had been measured. The misclose was .175 foot representing an error of 1/12,980. Both bases are about 15 feet above sea level and were measured with a 100-foot Konstant wire. All the angles were observed with a Troughton and Simms 5″ theodolite fitted with micrometer eye pieces reading to 10″ and estimating to 1″, and each angle was read times on each vernier, making a total of 12 readings. The largest error in any triangle is 13″ and this occurs in one only. The largest error in any of the other triangles hitherto observed is 9″. Any triangle with an error in excess of this will not be accepted and the 13″ error has not yet been corrected. 52 stations have been fixed and 33 of these have been valued; most of the others have been observed to and in some cases some observations have been taken from them. All observations have been taken on to flashes by a mirror in sunlight: no night work has been attempted.
The work would have been much more forward but for the heavy cloudy weather in May and June and the rains during the whole of the Summer.
The area covered by the triangulation already completed is about 15 miles North and South by 4 miles East and West.
5. Topographical Work. As it becomes necessary for the issue of lease plans or other purposes to make a survey of any neighbourhood so the filling in of the Ordnance Maps is taken in hand. Traverses, the error in which must not exceed 1/2,500 in the case of the 200 feet 1 inch maps and 1/3,000 in the case of the 50 feet maps, are run between triangulated points and any subsequent filling in will be done on these closed traverses. The work hitherto carried out is too disconnected to admit of any useful particulars of it being given.