How to Use Clinometer Compass

Clinometer compass combines two instruments: a compass for direction and a clinometer for measuring angles. Geologists and hikers often use them to measure the tilt of rock layers (dip) and their direction (strike).

Understanding the Parts:

Compass dial: This works like any regular compass, with a magnetized needle pointing north.

Clinometer scale: This is usually a curved scale with degrees marked, often integrated with the compass dial.

Sighting mirror (optional): Some clinometer compasses have a mirror that allows you to sight an object indirectly while keeping the compass level.

Here's a guide on how to find the dip and strike of a rock layer using a compass and clinometer, with images to illustrate the steps:

The exact order that you complete the steps and obtain the strike and dip of the plane is not crucial; this will depend on the instrument used, field conditions and personal preference. What is important is ensuring that you record the three pieces of information (strike, dip magnitude and dip direction).

Note that the order of the steps in Figures is different to take account of the easiest way to measure a dipping plane with the different instruments. If this technique is new to you, or the reading seems unreasonable, or the bedding surface is not ideal, take a second or even third reading and use the average or the best one.

Determining the Orientation of a Dipping Plane

Using a Compass and Clinometer to Find the Dip and Strike of a Rock Layer

1-General orientation

Find a good surface that is representative of the overall dip of the plane to measure. Determine the general direction of dip by looking at the plane or you can pour fluid over the bedding plane to see which way it runs.

In some cases it may be necessary to smooth out the variations on the surface by placing a notebook or clipboard on the bedding plane, but take care to ensure that this is not biased by a small irregularity. Hammer near left hand side shows the plane chosen in this case.

2. Set the clinometer mode

Prepare the compass-clinometer for the clinometer mode by setting the top of the clinometer part so that it is parallel to the long edge of the compass-clinometer (i.e. put the compass dial at 90–270°).

3. Dip magnitude

Place the long edge that is at the base of the clinometer scale on the bedding plane, with the long edge of the compass-clinometer parallel to where you estimate the maximum dip direction lies (i.e. pointing down the slope).

While looking at the clinometer reading, carefully rotate the compass-clinometer device slightly (as shown by the arrows) to find the line of maximum dip.

Determination of the Orientation of a Dipping Plane by the the Compass - Clinometer (Photos)

Read off the maximum dip. In this case it is 12°. Note that the dip can be read from either side of the Silva-type compass-clinometer.

4. Strike direction

The strike direction is exactly perpendicular to the dip direction, so remembering where the maximum dip lies, lift the compassclinometer and place the long edge of the compass-clinometer along the line of strike.

Pivot the compass-clinometer window (as shown by the red arrow) until it is horizontal.

Rotate the compass dial so that the compass needle lines up with the red outline for the north direction, checking that the compassclinometer is still horizontal. Take the reading of the strike from the dial. In this case it is 008° or the other end of the line, 188°.

You can double check that the strike direction is correct by placing the compass on its long edge along the strike line and checking that the dip is 0° (don’t forget to adjust the compass to the clinometer mode (step 2)).

5. Dip direction

The last measurement is the direction of dip to the nearest cardinal point (e.g. NW or SE, E or W). In this case it is E.

6. Record

Record the orientation of the plane in your notebook; in this case 008/12E. Note that the strike is always recorded as a 3-digit number to avoid any confusion and that the degree symbols are not normally shown to prevent any confusion with zeros.

Tips:

For accurate readings, ensure the compass clinometer itself is level.
Calibrate your compass clinometer regularly according to the manufacturer's instructions.
When using the mirror, be careful not to look directly at the sun.

Using the Mirror (optional):

If the slope is hard to reach directly, use the sighting mirror.

Hold the compass clinometer level and look through the peep sight.

Tilt the mirror until you see the object you want to measure (like the top of a tree) through the peep sight and the mirror.

The clinometer scale will be reflected in the mirror. Read the angle where the level indicator intersects the reflected scale.

By following these steps and practicing regularly, you can effectively use a clinometer compass for navigation, surveying, outdoor activities, and other applications requiring precise measurement of direction and angles.