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Strike and Dip Calculator

Strike and dip describe the orientation of a planar geologic feature such as bedding, foliation, cleavage, a fault, or a joint. Strike is the azimuth of a horizontal line on the plane. True dip is the steepest downward inclination of the plane, measured perpendicular to strike from 0 degrees horizontal to 90 degrees vertical. Because a strike line has reciprocal bearings, every record must state its convention. In the right-hand-rule convention used by this calculator, the plane dips to the observer's right when looking along the recorded strike azimuth, so dip direction equals RHR strike plus 90 degrees clockwise. A conventional RHR record such as 120/35 means strike 120 degrees and true dip 35 degrees toward 210 degrees. Quadrant notation expresses the same geometry with a strike quadrant, dip angle, and dip-direction quadrant. Apparent dip is the inclination visible in a vertical section whose azimuth is not necessarily perpendicular to strike. Its tangent equals the tangent of true dip multiplied by the absolute cosine of the angular difference between the section azimuth and dip direction. A section looking directly down dip shows true dip; a section along strike shows zero; every other vertical section shows an apparent dip between those limits. GeoMiner calculates the numerical geometry, draws an accessible compass diagram, and identifies whether the plane descends or rises toward the selected viewing azimuth. It does not validate the observation. A defensible field record preserves the original unconverted reading, feature type, station, location, date, observer, instrument, convention, north reference, magnetic declination or grid correction, facing or younging evidence, and uncertainty. Magnetic, true, and grid bearings are not interchangeable: magnetic declination varies with location and time, while grid convergence depends on the map projection and location. Metal, vehicles, phones, electrical infrastructure, magnetic minerals, poor exposure, irregular surfaces, weathering, instrument setup, and selecting the wrong plane can bias a measurement. A correct conversion cannot repair a poor observation. This tool is educational geometry rather than a survey, geotechnical design input, stereonet analysis, structural interpretation, resource model, or safety determination. The angles entered stay in the browser. Analytics retain only a bounded action,

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Verification resources

Cross-check terminology, classification, methods, and safety with these authoritative external resources.

  • undefined. Strike as the bearing, relative to north, of the horizontal line formed where a planar geologic surface intersects a horizontal surface.
  • undefined. Standard map symbols for bedding, foliation, cleavage, joints, and other planar observations, including right-hand-rule symbol orientation.
  • undefined. Right-hand-rule structural measurements, stereonet context, and the geometry used to calculate apparent dip in a chosen vertical section.
  • undefined. Dip as inclination below horizontal from 0 to 90 degrees and strike as clockwise azimuth from north from 0 to 359 degrees.
  • undefined. Magnetic declination as the location- and time-dependent angle between magnetic north and true north, needed when converting compass bearings to true bearings.

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Common questions

What are strike and dip?
Strike is the compass bearing of the horizontal line on an inclined planar geologic feature. Dip is the maximum downward inclination of that plane, measured perpendicular to strike from 0 degrees horizontal to 90 degrees vertical.
What is the right-hand rule for strike and dip?
Under the right-hand-rule convention, the plane dips to the observer's right when looking along the recorded strike azimuth. Dip direction is therefore 90 degrees clockwise from RHR strike.
How is apparent dip calculated?
The tangent of apparent dip equals the tangent of true dip multiplied by the absolute cosine of the angle between section azimuth and dip direction. Apparent dip cannot exceed true dip and is zero along strike.
Can magnetic, true, and grid bearings be mixed?
No. Preserve the original reading and state the north reference. Magnetic declination varies with place and time, while grid convergence depends on the map projection and location.
Does the calculator validate a field measurement?
No. It checks numerical geometry and notation only. Instrument setup, magnetic disturbance, exposure quality, plane selection, uncertainty, feature type, and interpretation still require competent field observation.

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