THIS is how to use a Lensatic Compass - very simple, by The Map Reading Company on YouTube. 59 min 57 s.
- Video length
- 59 min 57 s
- Time to do it
- 30 minutes
- Difficulty
- Medium
- Steps
- 8
What you need
Steps
Open the compass and check the parts. The lens arm has a sighting slot, the rear sight has a small hole, and the dial floats on a jewel bearing. Hold it flat so the dial spins freely.
Pick a clear ground feature ahead of you, such as a lone tree, a building corner or a hilltop. Choose something you can still see when you look up from the compass.
Raise the compass to your eye and look through the rear sight hole at the front sight wire. Line the wire up on your chosen feature.
Lower your eye to the dial and read the number under the fixed index line. That number is your bearing in degrees. Write it down.
To take a bearing from the map, lay the compass edge along the line from your position to the target. Turn the dial until the orienting arrow points to grid north on the map.
Read the bearing at the index line, then adjust it for magnetic declination if your area has a large difference between grid and magnetic north.
To walk the bearing, hold the compass level and turn your body until the red magnetic needle sits inside the orienting arrow. Look up, pick a feature on that line, and walk to it.
Repeat the sighting every few minutes and at each new landmark. If you drift, take a back bearing by adding or subtracting 180 degrees and walk back onto the line.
Tips and common mistakes
Keep metal objects, phones and magnets away from the compass, as they pull the needle off true north.
Walk to a distant feature rather than staring at the dial, and re-check the bearing at each stop.
Practise on familiar ground first so you can see your mistakes without getting lost.
In the UK declination is small, but check it before travelling abroad where it can be several degrees.
Questions
What is the difference between a bearing and an azimuth?
They mean the same thing here: the angle in degrees from north to your target. Some people use azimuth for the number and bearing for the whole skill.
Do I need to adjust for declination?
Only if the gap between grid north and magnetic north is large where you walk. In the UK it is small, but in places like western Canada or parts of Africa it can throw you far off course.
How do I find my location on the map?
Take bearings to two or three features you can identify on the map, then draw those lines back from each feature. Where the lines cross is roughly where you stand.
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.
