K value, abbreviated as K, is the horizontal distance required to achieve a 1% change in the slope of the vertical curve.
Curvature correction (K) in geodetic surveying, is when measuring distances over longer distances (such as across the Earth's surface), the Earth's curvature needs to be taken into account. The curvature correction factor accounts for the curvature of the Earth and is used to adjust the measured distance to the horizontal distance that would exist on a flat plane.
K Value Formula |
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\( K \;=\; \dfrac{ L }{ A }\) (K Value) \( L \;=\; K \cdot A \) \( A \;=\; \dfrac{ L }{ K }\) |
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| Symbol | English | Metric |
| \( K \) = rate of vertical curvature | \(ft\) | \(m\) |
| \( L \) = length of vertical curve | \(ft\) | \(m\) |
| \( A \) = algebric difference in grade (%) | \(dimensionless\) | \(dimensionless\) |
