How to Use a Lensatic Compass

How to Use a Lensatic Compass
The lensatic compass--also called a military compass--is a precision instrument that when used with a topographical map can guide the adventurous off marked trails into wilderness areas with confidence. The lensatic compass is used to set course bearings, orient yourself to a map and follow a course over land. Carrying and being able to navigate with a map and lensatic compass is a good idea, even when you are traveling with a GPS unit. Electronics do fail, so being able to get to your destination safely with a map and compass is an invaluable skill.

Instructions

Difficulty: Moderate

Taking a Compass Bearing

Things You’ll Need:
  • Lensatic compass
  • Topographical map
Step 1
Open the lensatic compass so that the cover is at a 90 degree angle and the lens bracket is at a 30 degree angle to the case. Check to make sure the dial is floating freely.
Step 2
Insert your thumb into the thumb loop.
Step 3
Hold the lensatic compass so it is resting on your thumb and bent index finger.
Step 4
Raise the compass to eye level.
Step 5
Line up a distant object with the sight wire and the center of the sighting groove in the lens bracket.
Step 6
Read the course bearing (azimuth) while keeping your head and compass still. There are two sets of numbers; degrees are in red and mils are in black.

Set a Course

Step 1
Open the lensatic compass completely.
Step 2
Place the compass on a level map with the azimuth directly under the index line. If you want to follow a 90 degree bearing, put the 90 degree mark under the index line.
Step 3
Hold the compass in this position and rotate the bezel until the luminous indicator is over the north "N" arrow. The course is now set. To check your course, open the compass and line up the luminous indicator with the "N" arrow. Do not move the bezel.

Following a Course

Step 1
Open the lensatic compass with the cover at a 90 degree angle and the lens bracket at a 30 degree angle to the case.
Step 2
Point the compass along the desired course bearing.
Step 3
Line up an easily identifiable object with the sighting groove and the sighting wire.
Step 4
Keep this object in sight as you travel.

Tips & Warnings

 
Practice using the lensatic compass using known courses.
 
If you lose sight of your distant object when following a course, immediately stop and locate a new object to guide you.
 
If there are no objects to sight when following a course, find one to the side. When you reach the object, travel perpendicular to your course of travel to get back on course. Sight a new object and resume travel.
 
Never use a compass on or near metal or magnetic fields. This will affect the accuracy of your readings.

Article Written By Mark Quest

Mark Quest began his writing career in 2009, contributing to various online publications. He attended Asheville Buncombe Technical Community College, focusing on the sciences.