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Dip & Dip Direction to Trend & Plunge Converter

Convert a plane's dip and dip-direction into the trend and plunge of its pole (normal line), and read off the strike. Poles are how planar structures are plotted on stereonets, so structural geologists constantly move between plane and pole orientations. Handy for stereonet work, structural logging and rock-mass characterisation.

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How to use this calculator

Enter Values

Enter your values and press Calculate to see results.

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How to use this calculator

  1. Enter the dip of the plane (0–90°).
  2. Enter the dip direction as an azimuth (0–360°, clockwise from north).
  3. Read the pole trend, pole plunge and the strike; all values are decimal degrees.

How it works

A plane's pole is the line perpendicular to it. Because the pole leans in the opposite direction to the dip, its trend (azimuth) is the dip direction plus 180°, wrapped to the 0–360° range. Its plunge is 90° minus the dip: a gently dipping plane has a steeply plunging (near-vertical) pole, and a vertical plane has a horizontal pole.

The strike is the horizontal line in the plane, at right angles to the dip direction: strike = dip direction − 90° (wrapped to 0–360°). Working with poles instead of planes lets you plot each structure as a single point on a stereonet, which makes clustering and set analysis far easier.

Worked example

Plane dipping 40° toward 120°. For dip = 40° and dip direction = 120°: strike = 120 − 90 = 30°; pole trend = 120 + 180 = 300°; pole plunge = 90 − 40 = 50°. So the pole plunges 50° toward 300°, i.e. up-dip and opposite to the way the plane dips.

Common mistakes

  • Giving the pole the same trend as the dip direction — the pole plunges opposite, so add 180°.
  • Confusing dip direction (down-dip azimuth) with strike (90° away from it).
  • Using pole plunge = dip instead of 90° − dip; a shallow plane has a steep pole and vice versa.

Frequently asked questions

How do I find the pole (trend and plunge) of a plane?

Pole trend = (dip direction + 180°) mod 360°; pole plunge = 90° − dip. The pole is the normal to the plane and leans opposite to the dip.

What is the strike from dip direction?

Strike is perpendicular to dip direction: strike = (dip direction − 90°) mod 360°. A plane dipping toward 120° strikes 030°–210°.

Why does the pole plunge opposite to the dip?

The pole is perpendicular to the plane. As the plane tilts one way, its normal tilts the other way, so the pole's trend is 180° from the dip direction.

Are the inputs and outputs decimal degrees?

Yes. Dip and dip direction are entered as decimal degrees, and strike, pole trend and pole plunge are returned as decimal degrees. Azimuths run 0–360° clockwise from north.

Why plot poles instead of great circles?

A pole is a single point on a stereonet, so many structures plot as a point cloud whose clusters reveal joint or bedding sets far more clearly than overlapping great circles.

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