<P> Strike and dip refer to the orientation or attitude of a geologic feature . The strike line of a bed, fault, or other planar feature, is a line representing the intersection of that feature with a horizontal plane . On a geologic map, this is represented with a short straight line segment oriented parallel to the strike line . Strike (or strike angle) can be given as either a quadrant compass bearing of the strike line (N25 ° E for example) or in terms of east or west of true north or south, a single three digit number representing the azimuth, where the lower number is usually given (where the example of N25 ° E would simply be 025), or the azimuth number followed by the degree sign (example of N25 ° E would be 025 °). </P> <P> The dip gives the steepest angle of descent of a tilted bed or feature relative to a horizontal plane, and is given by the number (0 ° - 90 °) as well as a letter (N, S, E, W) with rough direction in which the bed is dipping downwards . One technique is to always take the strike so the dip is 90 ° to the right of the strike, in which case the redundant letter following the dip angle is omitted (right hand rule, or RHR). The map symbol is a short line attached and at right angles to the strike symbol pointing in the direction which the planar surface is dipping down . The angle of dip is generally included on a geologic map without the degree sign . Beds that are dipping vertically are shown with the dip symbol on both sides of the strike, and beds that are level are shown like the vertical beds, but with a circle around them . Both vertical and level beds do not have a number written with them . </P> <P> Another way of representing strike and dip is by dip and dip direction . The dip direction is the azimuth of the direction the dip as projected to the horizontal (like the trend of a linear feature in trend and plunge measurements), which is 90 ° off the strike angle . For example, a bed dipping 30 ° to the South, would have an East - West strike (and would be written 090 ° / 30 ° S using strike and dip), but would be written as 30 / 180 using the dip and dip direction method . </P> <P> Strike and dip are determined in the field with a compass and clinometer or a combination of the two, such as a Brunton compass named after D.W. Brunton, a Colorado miner . Compass - clinometers which measure dip and dip direction in a single operation (as pictured) are often called "stratum" or "Klar" compasses after a German professor . Smartphone apps are also now available, that make use of the internal accelerometer to provide orientation measurements . Combined with the GPS functionality of such devices, this allows readings to be recorded and later downloaded onto a map . </P>

Dip is expressed as a compass direction and strike is expressed as an angle