Accession No

2185

Brief Description

plane table alidade, by Baker, 1900-1925 (c)

Origin

Maker

Baker

Class

surveying

Earliest Date

1900

Latest Date

1925

Inscription Date

Material

metal (brass); glass

Dimensions

length 306mm; breadth 73mm; height 118mm

Special Collection

Provenance

Transferred from Department of Geography, University of Cambridge, Cambridge, England, 05/1969.

Inscription

Description Notes

Brass. Telescopic sight; rack and pinion focus moving eyepiece. Cross hairs. Axis pivots in vertical pillar. Scale marks 20˚ either side of zero. Clip releases base of pillar which hinges forward for carrying. Edge of base graduated 0-15cm and 0-6”. Table engraved on base Yards 1/2 50,000 10,000 - 0 - 31,000 and horizontally by 100. Diagonally over 10,000 - 0. Bubble on base.

References

Events

Description
Plane table alidade
A plane table is a flat square board, with a piece of paper attached to the top surface on top of which an alidade (sighting rule) is secured. The apparatus also requires a magnetic compass for orientation.

This allows for one of the most direct and convenient methods of surveying. Initially, a point is drawn to represent the first surveying station. Lines of sight to certain objects can then be taken with the alidade are marked on the paper using the rule. The table is then moved to the second location and oriented in the same way using the compass. The distance moved is represented on the paper by an appropriate scale. The same lines of sight are then taken again and the intersects of the two sight lines show where the object is. This process allows a plan of the site to be created.

18/10/2002
Created by: Saffron Clackson on 18/10/2002

FM:43373