Accession No
3277
Brief Description
plane table alidade, by Georg Friedrich Brander and Christof Kaspar Höschel, German, 1780 (c)
Origin
Germany; Augsburg
Maker
Brander, Georg Friedrich Höschel, Christof Kaspar
Class
surveying
Earliest Date
1780
Latest Date
1780
Inscription Date
Material
metal (brass); glass
Dimensions
length 486mm; breadth 77mm; height 180mm
Special Collection
Provenance
Purchased from Christie's, London, England; lot 213, 12/12/1985.
Inscription
‘Brander u. Hoschel in Augsburg’ (centre of protractor)
Description Notes
Brass surveyors level. Telescope has draw-tube focusing and is fitted with 2 levels each with half a pin-hole sight and etched glass hair line. Telescope mounted on a vertical half-circle engraved with 3 scales: Cathetus 0-100 (x2), Bases 0-100 (x2), and 0-90 (x2). Plumb-bob suspension point on the axis, adjustable via a knurled nut and internal gear and rack. Vernier scale engraved 0-30 and 30-40 over Bina Minuta. Raised by a shaped support with 2 securing bolts on a plane-table rule (Bayrischer Landschuh) with chamfered edge.
Incomplete (eyepiece missing).
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:43475
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