Camera Surveying

[This article explains the preparation of the camera for taking the pictures at each of the three stations, after which the plates are developed, printed and kept until a convenient time may be had for plotting the ground. The succeeding article will give in detail the making of the map from the photographs.-Editor.]

CAMERA surveying is simply plane-table surveying in which the landscape has been photographically picked up and carried indoors. It has the enormous advantage that one can obtain a record of the utmost fidelity in a small fraction of the time taken to do the field work of even a sketchy plane-table survey, and that plotting can be done in the comfort and with the conveniences of a drafting room. When the hours one can work are short or the periods of clear, dry weather are few and far between, a camera is an ideal surveying instrument. It sees and records with the click of the shutter.

Surveying by camera was proposed early in the infant days of photography ; but not until the eighties were photographic surveys commenced in earnest. With the extensive surveys of the Canadian Rockies by the Canadian government within the past decade and the topographic surveys of the Alps, the camera has very recently indeed achieved the dignity of being known as a "sure-enough" surveying instrument. Even today, few surveyors have ever used photography for making surveys, even though for mountain topography or any survey which includes a large number of distinctive, inaccessible landmarks, the camera asks no odds of either the plane table or the stadia transit.

A camera survey taken of the summer cottage or the camping ground will be a source of great delight while it is being plotted up of winter evenings. There is something weird in watching each tent and dock slip into its place with naught but a pair of dividers and a few pictures to do the trick. And when the map is done, there are all the data to tell just where a tennis court can go or a walk ought to be built.

In making surveys, a plate camera will do more accurate work than will a film camera; and a fixed focus is a big help in plotting. In spite of the special and expensive instruments which have been designed solely for surveying work, a little ingenuity on the part of the owner of most any kind of a camera, be it big or little, film or plate, box or folding, will do wonders toward producing good results.

To be used for surveying, a camera plate is vertical and when the perpendicular line from the center of the plate to the center of the lens is horizontal. Actual cross hairs in the camera are not as good as four tiny points of V's, one projecting from the middle of each side, top, and bottom of the camera box, just in front of the plate holder. How the level is to be adjusted so that a line between the upper and lower points will be truly vertical, and one through the die-side points truly horizontal and on a level with the center of the lens when the bubbles are in the center of the spirit level, will be described later.

must be fitted with a spirit level and some arrangement for cross hairs. A T-shaped level on the bed or the box, carefully adjusted, will show when the

Camera Surveying 16A T Shaped Level with Adjusting Nuts is Located on the Camera Box, or on the Bed of the Folding Camera

Ill: A T-Shaped Level with Adjusting Nuts is Located on the Camera Box, or on the Bed of the Folding Camera

To Prepare a Camera for Surveying, It is Necessary to Arrange That the Axial Center Line through Lens to the Plate Shall be Level

The Camera is Set Up, Complete with Thread or Pencil Line Cross Hairs and Level, Then Focused on a Stake so That Its Top will Just Come to the Horizontal Cross Hair at the Center of the Plate When the Level Tube Parallel with the Center Line of Lens Reads Level

Ill: The Camera is Set Up, Complete with Thread or Pencil-Line Cross Hairs and Level, Then Focused on a Stake so That Its Top will Just Come to the Horizontal Cross Hair at the Center of the Plate When the Level Tube Parallel with the Center Line of Lens Reads Level