CO129-505-13 Survey of Hong Kong 22-6-1927 - 13-12-1927 — Page 33

The Colonial Survey Committee.

Notes on the Survey of Hong Kong.

12

33

Inadequacy of the topographical maps.

Shortage of Trigonometrical

data.

Framework available for air photo survey.

In 1919, G.O.C.,Hong Kong. drew attention to the inadequacy of the mapping of Hong Kong and the Leased Territories. The maps were on varying scales and of different orders of accuracy. The only map which was at that time considered to be sufficiently accurate for military purposes was the 8" to the mile survey which covered only a part of the Leased Territories.

The War Office at that time was unable to send out a party to survey on the ground but was prepared to grid the existing maps and to incorporate any corrections which were sent home from Hong Kong. In the course of an investigation regarding the fitting of a grid on to the 34 24" and 8" to the mile maps, it was found to be impossible to grid them accurately using the trigonometrical points supplied.

Further information regarding these points and the projection used for the maps was asked for from the G.O.C.,Hong Kong. On 29th July, 1922, G.O.C.,Hong Kong reported that every effort to obtain positions of further trigonometrical points and information about the projection of the 8" to the mile map had been made but without result.

The 8", 2"

2", " to a mile maps were gridded during 1923 at the War Office but, owing to inaccuracies in the maps and the impossibility of obtaining further trigonometrical records, results were not satisfactory as the grids on the different maps did not agree relative to the detail. The 2" map was particularly bad in this respect.

In March, 1924, the opportunity of H.M.S. Pegasus being at Hong Kong for refitting was taken to photograph Hong Kong and the Leased Territories from the air. At this time the

information at the disposal of the War Office with regard to trigonometrical framework was that the triangulation available consisted of 3 parts:

-

(i) King's Triangulation covering the area of

the 8" map. This was thought to be good.

(ii)

Tate's Triangulation covering the rest of the Leased Territories, Mich, was not properly marked on the ground and most

of the points had been lost.

(iii) P.W.D.Triangulation. Replacing Tate's

work. This was properly marked but reports had been received which threw doubts on its accuracy. No vertical angles were observed on this triangulation.

Preparations/