CO129-505-13 Survey of Hong Kong 22-6-1927 - 13-12-1927 — Page 29

Framework available

for air photo survey.

Preparations for air photo survey.

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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:-

(11)

(1) King's Triangulation covering the area

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

Tate's Triangulation covering the rest

of the Leased Territories. This 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

In October,1924, a Colonial Survey

Section consisting of 1 officer and 3 other ranks

was sent out to do the necessary ground control

for the air photographs. Previous to this the

G.O.C., Hong Kong was instructed to ask the civil

authorities to cooperate by checking the P.W.D.

triangulation and extending it and marking it in

such a way that it would be visible from the air.

In September, 1924, a list of the

trigonometrical