plane table
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plane table
n.
A portable surveying instrument consisting essentially of a drawing board and a ruler mounted on a tripod and used to sight and map topographical details.
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plane table
Oxford Dictionary of the US Military:
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plane table
A surveying instrument used for direct plotting in the field, with a circular drawing board and pivoted alidade.
See the Introduction, Abbreviations and Pronunciation for further details.
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In surveying, a device for plotting the lines of a survey directly from the observations; consists essentially of a drawing board on a tripod, with a ruler, the ruler being pointed at the observed object by the use of a telescope or other sighting device.
Oxford Dictionary of Archaeology:
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plane table
[Eq]
A portable drawing board mounted horizontally on a tripod and used for surveying sites and earthworks by constructing a map directly onto paper or film attached to the board. With the board positioned directly above a survey station whose position is marked on the paper, an alidade is used to sight onto a target point. A line can then be drawn along the straight edge of the alidade and the distance from the survey station to the target point scaled off to fix its position. If measurement is not possible, then two survey stations a set distance apart can be used to triangulation the target point as the intersection of the two alidade-defined lines. Plane-table surveys have the distinct advantage that the surveyor can fill in detail by eye as the work progresses.
Wikipedia on Answers.com:
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Plane table
A plane table (plain table prior to 1830)[1] is a device used in surveying and related disciplines to provide a solid and level surface on which to make field drawings, charts and maps. The early use of the name plain table reflected its simplicity and plainness rather than its flatness.[2]
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Contents
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History
The earliest mention of a plane table dates to 1551 in Abel Foullon's "Usage et description de l'holomètre", published in Paris.[3] However, since Foullon's description was of a complete, fully developed instrument, it must have been invented earlier.[2]
A brief description was also added to the 1591 edition of Digge's Pantometria.[3] The first mention of the device in English was by Cyprian Lucar in 1590.[1]
Some have credited Johann Richter, also known as Johannes Praetorius,[4] a Nuremberg mathematician, in 1610[5] with the first plane table, but this appears to be incorrect.
The plane table became a popular instrument for surveying.[2] Its use was widely taught. Interestingly, there were those who considered it a substandard instrument compared to such devices as the theodolite, since it was relatively easy to use.[1] By allowing the use of graphical methods rather than mathematical calculations, it could be used by those with less education than other instruments.
Plane table construction
This shows a plane table with part of the surface of the table cut away to show the mounting on the tripod. The mount allows the table to be levelled. On the table, the alidade with telescopic sight is seen
A plane table consists of a smooth table surface mounted on a sturdy base. The connection between the table top and the base permits one to level the table precisely, using bubble levels, in a horizontal plane. The base, a tripod, is designed to support the table over a specific point on land. By adjusting the length of the legs, one can bring the table level regardless of the roughness of the terrain.
Use of a plane table
In use, a plane table is set over a point and brought to precise horizontal level. A drawing sheet is attached to the surface and an alidade is used to sight objects of interest. The alidade, in modern examples of the instrument a rule with a telescopic sight, can then be used to construct a line on the drawing that is in the direction of the object of interest.
By using the alidade as a surveying level, information on the topography of the site can be directly recorded on the drawing as elevations. Distances to the objects can be measured directly or by the use of stadia marks in the telescope of the alidade.
References
- ^ a b c Turner, Gerard L'E., Scientific Instruments 1500-1900, An Introduction, University of California Press, 1998 ISBN 0-85667-491-5. This is an updated version of his earlier Antique Scientific Instruments Blandford Press Ltd. 1980, ISBN 0-7137-1068-3
- ^ a b c Kiely, Edmond, Surveying Instruments: Their history and classroom use, Bureau of Publications, Teachers College, Columbia University, 1947. page 228
- ^ a b Turner, Anthony, Early Scientific Instruments, Europe 1400-1800, Sotheby's Publishing, 1987, ISBN 0-85667-319-6. page 81
- ^ Vai, Gian Battista, Caldwell, W. G. E. The Origins of Geology in Italy Google books online copy
- ^ Laussedat, Amié, Recherches sur les instruments, les méthodes et le dessin topographiques, Paris, 1898-1902, two volumes
- Raymond Davis, Francis Foote, Joe Kelly, Surveying, Theory and Practice, McGraw-Hill Book Company, 1966 LC 64-66263
External links
- Telescopic Plane Table Alidade in the collection of the Smithsonian National Museum of American History. This image shows the bubble levels on the base.
- http://www.sciencemuseum.org.uk/objects/surveying/1933-7.aspx
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American Heritage Dictionary
The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2009. Published by Houghton Mifflin Company. All rights reserved.
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Oxford Dictionary of the US Military
The Oxford Essential Dictionary of the U.S. Military. Copyright © 2001, 2002 by Oxford University Press, Inc. All rights reserved.
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McGraw-Hill Dictionary of Architecture & Construction
McGraw-Hill Dictionary of Architecture and Construction. Copyright © 2003 by McGraw-Hill Companies, Inc. All rights reserved.
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Oxford Dictionary of Archaeology
The Concise Oxford Dictionary of Archaeology. Copyright © 2002, 2003 by Oxford University Press. All rights reserved.
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