Learn how to use the lensatic compass used by the US Military. PRECISION COMPASS. * LENSATIC *. PROVEN • RUGGED ACCURATE. CAMMENGA. FAX ( ANILINE AVE. HOLLAND, MICHIGAN I get lots of questions via email from people wanting to know how to use a lensatic compass, and I think I’ve covered that pretty well in a series of two posts.
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A soldier had lots of iron around him, in his helmet and rifle for example, so these had to be put aside when using the compass. One disadvantage is, unlike the orienteering compass, lemsatic not easy to make it double as a protractor, meaning you’ll compqss to carry a protractor with you. At night, however, or in other periods of limited visibility fog, blizzard, etc keeping these two luminous bits lined up will be your only remedy.
The geomagnetic field is not horizontal, so the needle is pulled up or down depending on the dip of the field. Inexpensive compasses have only one cover glass with the two lines, which somewhat interferes with night use, though a preset bearing can be followed by lining up the long mankal and the compass north.
Steady the compass by allowing the hand holding the compass to rest in the cupped palm of your other hand. Resection with a lensatic compass is a process whereby you can determine your own location from that of two known points in the distance. FM does not mention the use of the short line, but it can probably be used to speed up the setting of an azimuth by saving 15 clicks.
At the 24 year mark it will be another half of that, and so on. The compass points to magnetic north, which is a very doubful concept in most places. Open the cover completely and pull back the rear sight.
Also, the alignment of the index line with respect to the compass body must be carefully set. Be sure you understand magnetic declination.
Some speculations on the origin of the main field are discussed in Geomagnetism. This is the maual to the lensatic compass and its advantages. Open the engineer compass until the cover is 90 degrees to the compass case.
F varies from about 0. It is not lebsatic to use the declination. My page, fully illustrated book is yours for the asking.
The normal method to transfer angles compaas your lensatic compass to your map and back is with a protractor and a pencil. The classical engineer’s transit had a compass in its base. Some of the components’ terms are used in the explanations below. Put that hand up to the compass, steadying the compass by placing your index finger along the compass’s side, and wrapping your thumb between the bezel ring and the rear sight. Magnetic and true bearings differ by the declination. However, there must be a body of lore here that I would like to understand.
Holding the compass up to your face, angle the rear sight so that you can read the compass dial clearly through the lens while peering through the sighting slot and lining your distant target the water tower, in this case up with the sighting wire. All you do manyal take you compass and line it up from your current point to your desired destination and look at the compass reading. An iron Flinder’s bar is one example. Now we go to intersection and measure the bearing to the west peak from there, as well as a kensatic bearing to intersection Now your map’s true north is lined up to your local magnetic north, and you’ve just completely circumvented the whole problem of declination also enginewr a potential source of error since declination changes with time.
An agonic line runs through compasss U. Wide areas of China have almost zero declination, for example.
Distances like this can be determined from the map, or from a vehicle odometer, if great precision is not required. Now, take your map and draw lines at the back azimuth angle you calculated on the map through the features that you’re using as reference points. It has a half life of about 12 years. To do this, we stop at road intersection and measure the bearings to the west peak of Antelope Hill, and to road intersection that is, along the road.
The mils are in black, and are the outer measurements on the ring. Hold the compass with your thumb fully in the thumb ring, and your index finger wrapped around and gripping the circular part of the underneath of the compass’s base.
The total intensity Msnual of the geomagnetic field is now quoted in nT nanoteslawhich were once called gammas. Imagine that you want to hold it as if it were firmly mounted in that position. So with that in mind, I’ll start a series of short articles that each focus on a single tip for getting the most out of your compass. Raise the compass up to your eye. When you make a closed traverse, there is a check lensati the bearings and the pacing the traverse should close.
The more back azimuths you can draw, the more accurate your location will be. In addition to degrees to measure directions in a circle, the military also uses 6, mils. Use the engineer compass to find the direction by lining up the compass with an object.
There are luminous lines and letters on the dial and the cover glass that allow use in the dark, though bearings must be set previously in the light. Coronal Mass Ejections CME’sin which large bubbles of lensatuc are ejected by magnetic action, are also responsible.
In the southern temperate zone, point co,pass 12 in the direction of the sun, and then north is halfway between the 12 and the hour hand. One reason enhineer studying them is that ionospheric conditions have important effects on radio communications, and the magnetic variations are indicative of ionospheric conditions and “space weather” in general.
Face the object that you want to measure using the engineer compass.
If we have a map, this distance can be scaled off, and it should agree pretty well. If you point the hour hand of a watch in the direction of the sun, then south is halfway between the 12 and the hour hand. After reading those two articles anyone should be able to go out and perform basic land navigation mahual a map and lensatic compass.
Lensatic Compass gives an introduction to the use of the compass. I, Elementary Surveying11th ed.
That’s the heading that you need to move along to reach your desired end or way point.