A clinometer is a simple device that can be used to measure the altitude of an object. Despite its simplicity, a clinometer provides a level of accuracy sufficient to measure angles to the nearest degree. A ‘mini-clinometer’ as shown below, can be constructed very easily and cheaply and is small enough to stow in a ruck sack or boat emergency ‘grab bag’.
- Short wooden or plastic baton (approx. 40 cm in length).
- 1 drinking straw.
- Short piece of string.
- Small weight such as a fishing-line weight.
- A school protractor.
- Strong glue (suitable for sticking wood to plastic).
- A piece of smoked glass (see note 3 under ‘Method of Use’ below).
Suggested Method of construction (see diagram).
- Glue baton onto protractor as shown in the diagram. (Note. If you are unable to find a protractor that is marked in the same way as the one in the diagram, simply change the numbers with an indelible pen).
- Glue drinking straw to top of baton as shown in the diagram.
- Make a plumb-line from the string and weight and attach to protractor as shown in the diagram.
Method of Use.
- Holding the instrument by the baton, sight the target object through the drinking straw (rather like a telescopic rifle-sight).
- Hold the device as steady as possible and ask a partner to read off and record the angle indicated by the plumb-line. This will be the angle of elevation of the object above the horizon. If you are alone, simply clamp the string against the side of the protractor with a spare finger as soon as you are lined up with the object and then read off the angle indicated by afterwards.
- If available, a piece of smoked glass should be used when measuring the altitude of the Sun to avoid damaging a person’s eyesight. This would obviously be difficult for a single person but if you are in company, ask a colleague to hold the smoked glass in front of the Sun for you. (If a piece of manufactured smoked glass cannot be obtained, simply hold a piece of glass in the smoke of a candle or oil lamp until it is covered in a layer of smoke residue).
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