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Maps of Hong Kong
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taxation. The detail field work was done by Indian Surveyors under the guidance of two European officers, supplied by the Survey of India. When this Cadastral survey was completed it was thought that a topographical map should also be made. The proportion of cultivated land in the Ter- ritory (about one-sixth of the total area) was so small that the cadastral maps showed large blank spaces between small patches of surveyed land. These blank spaces however were to some extent occupied by trig, stations, and with their help the intervening hills were sketched in. The map produced was on the scale of 2 inches to the mile. The hills were shown by contours 100 feet apart.
These contours were sketched in between the few trig. stations on the hill tops and the patches of cultivated land in the valleys. The result was a map of varying degrees of accuracy. In places where the valleys were straight and the slopes uniform the work was easy. But in the jumble of hills and valleys (pays accidenté is the very expressive French term), which makes up the greater part of the Territory the work was diffi- cult and the map produced was in places so inaccurate that when the Geological Survey was undertaken a few years ago, the Canadian geologists in charge of that work were often unable to fit the geological features onto the topographical map. As an instance of this inaccuracy, it may be men- tioned that the island of Chu lu kok (Chik lap kok) north of Lantao, is shown by the contours as 1,000 feet high. It should be 500 feet.
The Military Authorities found this map inadequate and commenced a survey of the southern part of the Territory and issued a contoured map on the scale of 21⁄2 inches to the mile. This map was first published in pre-war days. Its later editions included Hong Kong Island, most of Lamma Island, and the mainland as far east as Port Shelter and as far north as Tai Po and ended westward a few miles beyond Tsun Wan (Tsung Wan). A marginal note on this map tells us that the contours on the mainland are surveyed, those on the islands approximate only." Hong Kong is an island and a patch of about half a square mile to the south of Butterfields reservoir is certainly a good example of this "approximate" work. Neither the hills nor the valleys can be identified on the ground. The mainland part of the map appears good work. It is a curious anomaly that Hongkong Island the most important part of the colony should be the worst mapped.
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The great war stopped this work but brought out the method of aerial surveying and in 1924-1925 aeroplanes were at work taking the neces- sary photographs for a new map. The result of this work is a map of Hong Kong and the leased Territory on the ample scale of 1/20,000, nearly 3 inches to the mile with contours at 10 metres apart.
Surveys by photos from the air have been found of great value in places which are difficult of access e.g. The Amazon forests (1) and the Irrawaddy Delta (2). These however are flat districts and it is not clear how the system will serve for the survey of South China hills where the contours are the main topographical feature. Only an examination on the ground would show to what degree of accuracy, in this respect, the system has worked out. The air map would no doubt be of great help to the con- tour drawer in showing all the little gullies or water courses which in the old 2 inch map were sketched on, often very inaccurately.
May 1932.
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