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Distance Between Two
Points
Classes of Level
Precision of Levelling
Two Peg Test
Field Procedures
Procedural Rules
Reduction Methods
Adjustment of Misclosure
Two Peg Test
All instruments are subject to errors of calibration and adjustment. In the case of levelling instruments the main source of instrumental error is where the line of sight, produced by the cross hairs in the telescope, is not parallel to the horizontal line of collimation produced by the manufacture of the instrument. This error is known as collimation error as it effects the line of collimation. The test that we undertake in order to determine the amount of errror and then eliminate it from our measurement is known as the two peg test.
Two Peg Test Method