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True dip versus apparent dip

Short answer

True dip is the maximum inclination of a bed measured perpendicular to strike. Apparent dip is measured in any other direction and is always less, given by tan(δ_a)=tan(δ)×sin(α) where α is the angle between the section and strike.

Differentiate between true dip and apparent dip.

PointTrue dipApparent dip
DefinitionMaximum inclination of a bed measured in a direction perpendicular to the strikeInclination of the bed measured in any direction other than perpendicular to the strike
DirectionAt 90° to the strikeAt any angle between 0° and 90° to the strike
ValueGreatest dip of the planeAlways less than the true dip (zero along strike)
Seen inSection perpendicular to the strikeCuts, boreholes and sections oblique to the strike
RelationTrue dip is a constant for a planetan⁡δa=tan⁡δ×sin⁡α\tan \delta_a = \tan \delta \times \sin\alpha, where α\alpha is the angle between the section and the strike

✓ Answer checked by Claude Opus 5.5 (high effort)

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