How To Measure A Mountain With A Compass, by The Map Reading Company on YouTube. 20 min 14 s.
- Video length
- 20 min 14 s
- Time to do it
- 30 minutes
- Difficulty
- Medium
- Steps
- 8
What you need
Steps
Stand at a spot with a clear view of the summit. Hold the compass flat and level in front of you so the needle swings freely.
Sight the summit over the compass and turn the dial until the orienting lines sit under the needle. Read the bearing in degrees and write it down.
Walk a measured straight line away from the summit, for example 100 paces, keeping the summit in view. Note the new bearing to the summit from this second point.
Subtract the two bearings to get the angle between them. This angle, plus your measured distance, lets you draw or calculate the triangle to the summit.
Use the triangle to find the straight line distance to the summit. With a right angle you can use distance = baseline divided by tan of the angle.
Estimate walking time with Naismith's Rule: about 1 hour for every 5 km plus 1 hour for every 600 m of ascent.
To get the height, take a bearing to the summit and tilt the compass to read the angle of elevation, or use the clinometer scale if your compass has one.
Write down the elevation angle. Height above you = distance to the summit multiplied by tan of that angle. Add your own altitude to get the summit's height.
Tips and common mistakes
Take both bearings from the same spot if you can, and keep the compass level or the angle will be off.
Pace out your baseline carefully; a wrong distance throws off both the range and the height.
Use a map or GPS to confirm the summit height so you can check your maths.
Stay on safe ground with a clear view and avoid steep edges while you sight and pace.
Questions
Do I need a map for this method?
No. The compass bearings and a measured baseline give you the distance and height. A map helps you check your answer and find your own altitude.
What if my compass has no clinometer?
You can still find the distance with two bearings. For height, use a phone level app or estimate the angle and apply the tan formula.
How accurate is this compared with a map?
It is a rough field estimate. Small errors in pacing and angle reading add up, so treat the result as close, not exact.
This guide was drafted from the video's details and general task knowledge. It has not been checked against the full video. Check the video and relevant product instructions before following a procedure. Report a correction.
