AERIAL SURVEYING

Evening Post, Volume CXXV, Issue 146, 23 June 1938, Page 15

AERIAL SURVEYING

MODERN METHODS

Things are not always what they seem when seen in photographs taken from the air for surveying purposes. A yellow cornfield, for instance, may come out in the photograph black, owing to the shadows of the stalks; lakes or ponds may also be black; fences may look like drains, and vice versa; and slopes may take on all kinds of appearances according to the sunlight falling, upon them. To interpret details in photographs taken from the air for surveying purposes requires experience, and an ordinary survey map is a great help in interpretation. This much and a great deal more was made clear last night by Mr. G. T. Bailton, of the aerial survey branch of the Lands Department, when he was speaking to members of the Wellington Philosophical Society on modern methods used in aerial survey work.

The aerial method of making topographical surveys, Mr. Railton pointed out, was the most economical method. Two kinds of photographs could be taken for these surveys, vertical and oblique. The former provided a true plan to scale, while the latter did not, although it had other advantages. In New Zealand vertical photographs were taken for plotting methods. With the aid of lantern slides, the speaker explained details of the methods employed, the types of cameras used in this and in other countries, how mosaics are fitted together, and how plotting machines, costing up to £3000 each, are used in making the maps constituting the finished aerial survey.