Chains and Tapes

Offset Tape

Stylon Tape

Chain

Other Equipment
Survey Methods
Catenary (Sag) Correction

 
 

If the tape cannot be supported for its length then it will hang freely under the influence of gravity. The shape the tape will take is known as a catenary and can be determined mathematically.

The correction is:

DL = -( Mg )2l3 or, for steep slopes, DL = -( Mg )2l3 cos2b
24T2 24T2

For example, for a catenary of 30m, a tension of 50N and a mass per unit length of 0.011kg/m;

DL = -( 0.011 x 9.8 )2 x 302
24 x 502
= 0.005 m

The tension must be measured with a spring balance for this correction to be determined.
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Maintained by:

Joiana Nascarella, Department of Geomatics.
Email: jlnasc@yahoo.com

Created: 27 January 2000
Last modified: 17 March 2000 		Authorised by:
Mark Shortis, Assistant Dean, Computing and Multimedia, Faculty of Engineering.

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Department of Geomatics, University of Melbourne.