**Sag or Catenary Correction**

When taping between
two points, the tape often ends up suspended above the ground (suspended
in *Catenary*), due to the
height of the marker points. This results in the tape sagging.

Correction = ** -** w(squared) L(cubed) cos (squared)(
theta) / 24 Tf (squared)

where **L** is the measured length and **(theta)** is the
angle (from horizontal) of the slope between the points. Also,
**w** is the unit weight of the tape, and **Tf** is the applied
tension.

This value should then be added to the measured ground distance.

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