The sighting optic can be adjusted to suit your eyesight. A web search revealed a lot about compasses and geomagnetism, but no good explanation of the lensatic compass. Disadvantage of chain surveying is that, in it only distances are measured and hence area is to be covered with a network of triangles. Put the map on a level surface such as the ground, and place the compass on top. There are a variety of different types and models of compasses, such as baseplate, sighting, prismatic, and electronic. Difference between prismatic compass and surveyors compass november 4, 2017 january 26, 2018 by kathir 6 comments. The table below lists the steps to perform the centerhold technique. The british mk iii compass is a good example of a prismatic compass. Aline or plane passing through geographical north pole and geographical south pole magnetic meridian. Cammenga precision lensatic instructional booklet pdf download. How to drawing a prismatic compass prismatic compass part. This type of compass is a light and simple instrument and is used for rough surveys where too much accuracy is not necessary.
The branch of surveying in which direction of survey line are determine by a compass and their length by a chain or tape is called compass surveying. In the center of the compass box, is a pointed steel pivot is used. A lot of compasses are called prismatic when they are not. How to use a military style sighting compass gone outdoors. Dec 09, 2018 prismatic compass readingprismatic compass pdf. Place the fully opened lensatic compass on map with the scale edge alongside the magnetic north line of the declination diagram. Theyre also called military compasses because this is the design used by the us military. It protects the compass and forms entire casing or body of the compass. Compass surveying is a type of surveying in which the directions of surveying lines are determined with a magnetic compass, and. A prismatic compass uses a prism to allow the reading of the card and viewing of the object of interest together, hence the name. While the compass needle and the eye sight vane can be rotated the graduations are made in such a way.
Open the compass cover at a 90degree angle and then set the lens bracket at a 30degree angle. Generally, the prismatic compass is designed to handle heavyduty use, and it is both air and watertight. The term lensatic refers to the magnifying lens that helps you use the compass more effectively. When the compass is used, the rose can be aligned with the corresponding geographic directions. Lift the compass, and make sure it is at your eye level. The use of compass as a navigator is a practice followed for centuries. Military map reading this booklet is to help qualified defence map reading instructors in unit map reading training and testing.
How to use a lensatic military compass navigate safely in. The rear lens flips out when the compass is open, and is used to read the dial. Unfold the compass entirely, so the sighting wire is level with the map. Next, rotate the entire thing map and compass until your compass is telling you that its pointing north. Such survey does not require the formation of a network of triangles. How to use a lensatic military compass navigate safely. However, just because you have a compass does not mean you know how to use one. The lensatic compass is was the typical military field compass, and is used principally to measure or lay out magnetic bearings. Jun 06, 2017 a military training film supervised by an officer appointed by the general staff. Rotate the map and compass together until the needle and the map both point directly. A compass is an instrument used for navigation and orientation that shows direction relative to the geographic cardinal directions or points. Prismatic compass this is a more expensive type of compass with a prism which enables a compass bearing to be taken while sighting your objective. The two basic techniques for using the lensatic compass are the center hold technique and compass tocheek technique.
The prismatic compass was invented by charles schmalcalder and patented in 1812. Put your thumb into the thumb loop, which is located on the side of the compass. This compass is made into a box which is circular and 85 to 110 mm in diameter. It can be more accurate than other compasses but it is harder to use and therefore should only be used once the basic principles of map and compass work have been mastered. In chain surveying, the positions of main stations and directions of main survey lines are fixed by tie lines and check lines. Prismatic compass definition is a surveyors hand compass provided with a triangular glass prism so adjusted that the compass can be read while taking a sight. Linear measurements refer to horizontal distances measured by chain or tape. The two basic techniques for using the lensatic compass are the center hold technique and compasstocheek technique. When the magnetic needle is suspended freely and balanced properly, unaffected by magnetic substances, it indicates a direction. Dec 30, 2014 uses of prismatic compass the prismatic compass is a small instrument which is held in the hand for observing, and is there employed on the rougher classes of work.
Open the compass cover containing the sight to a vertical position, making it form a right angle with the dial portion of. The effects of iron ships on the compass needle, with their permanent and induced magnetism, are very complicated to describe and have been the subject of much study. Milsurps knowledge library compass, prismatic, mk3 by. How to use a prismatic compass sigg g ghting a bearing the compass is simply aimed at an object or direction. A diagram always helps to keep the direction of the declination straight. How to drawing a prismatic compass prismatic compass. The least count of line prismatic compass observed by 30 mm. Military compasses and those designed similarly are simple to use and can be found at many outdoors supplies or military surplus stores. This type of survey can be used to measure large areas with reasonable speed and accuracy. Compass, prismatic, mk3 by peter laidler i am a compass maker by trade, and this article, while obviously written in good faith, gives fatally flawed information that will lead people to carry out work on beautiful, precision instruments, that will do such damage as to possibly render the compass beyond economical repair. Plane table survey principles, advantages and disadvantages, equipment, accessories and their uses. Constructed with metal, the eyeskey compass is waterproof and shakeproof, and according.
This compass is known throughout the world for its precision, reliability, versatility, ruggedness and much more. The prismatic compass and how to use it 1917 compass. Adjust the map with compass on it so that the compass cover points to magnetic north north arrow of compass is pointing directly to the index line. Rotate azimuth ringg g to align north box the needle by viewing in mirror.
Prismatic compass is a portable magnetic compass which can be either used as a hand instrument or can be fitted on a tripod. The graduation start from zero marked at south end of the needle and they run clockwise so that 90, 180, 270 where marked written are interval. She has been studying health and fitness issues for more than 10 years. Uses of prismatic compass the prismatic compass is a small instrument which is held in the hand for observing, and is there employed on the rougher classes of work. There are two methods to using a military compass, the center hold technique or the more accurate compasstocheek technique. Difference between prismatic compass and surveyors compass. Aug 30, 2007 this lovely chap, stuart, will repairrefurbishclean a stanley g150 prismatic compass for a reasonable price.
Prismatic compass definition of prismatic compass by. This chapter focuses on using a baseplate compass because it is a common, inexpensive. Cylindrical metal box cylindrical metal box is having diameter of 8 to 12 cm. Lay the compass down on the map so its long side is parallel with the northsouth axis of the map. How drawing a prismatic compass with full details i drawing this math calculation see this link. Since 1848, pyser optics have been manufacturing the finest, highest quality range of liquid prismatic compasses in the world. But when the area is large, undulated and crowded with many details, triangulation which is the principle of chain survey is not possible.
Some are illuminated with the assistance of a small battery, while others use photoluminescent materials to make the dial visible in low. Jul 11, 2019 lensagic ships compass has a rotating graduated disc, like the lensatic compass, and the fixed index is called the lubbers line. The primary source is the manual of map reading and land navigation, army code 71874. The graduations on the compass are located on a light aluminum ring fastened to a needle such that the zero point on the graduation scale coincides with the south point of the needle. Compass surveying the prismatic compass the prismatic compass is a magnetic compass which consists of the following parts. A lensatic compass, also called a military compass, is a more advanced and useful version of a magnetic compass. Prismatic compass surveying pdf notes expert civil. The traditional milspec liquid prismatic compass is currently in service with numerous armies around the world, built to meet the exacting accuracy and high specifications demanded by users worldwide. Coming across an old fm2125, elementary map and aerial photograph reading, from 1944 reminded me of the lensatic compass, an instrument not as commonly known these days as it once was. A rare original ww1 british military compass manual, published in 1917 by the scientific instrument makers, e. A prismatic compass is a navigation and surveying instrument which is extensively used to find out the bearing of the traversing and included angles between them, waypoints an endpoint of the lcourse and direction. Step action 1 open the compass so that the cover is fully extended. A military training film supervised by an officer appointed by the general staff.
There may be a good site out there, but some i tried had vanished, and the rest were by people who. This was the only means through which directions and the horizontal measurements are made, before the invention of a theodolite or sextant. Many models can be mounted on a tripod when appropriate, as well as held and operated in one hand. Prismatic compass surveying pdf notes download compass surveying prismatic compass compass traversing important definition true meridian.
Let the compass rest on your thumb and index finger. Produced for the directorate of army kinematography by publicity picture pr. The difference between the bearings will be the declination. The prismatic compass has been designed to give accurate magnetic headings.
Dec 15, 2017 the use of compass as a navigator is a practice followed for centuries. Prismatic compass the graduated ring remains stationary as it is attached to magnetic needle. The greatest advantage of this compass is both sighting and reading can be done simultaneously without changing the position. Make sure that the sighting wire of the compass is perfectly parallel to any northsouth lines on the map. It is circular in shape and its diameter is 110 mm.
X old steering mark correct back azimuth 340, 5040 mils alternate steering mark 167, 2970 mils. A compass is an instrument that is used for navigation and mapping because it measures the geographic. Introduction the instructions in this booklet are for the cammenga lensatic compass currently being distributed by the u. The magnetic bearings of the lines are measured by prismatic compass and the distances of the lines i. Sep 01, 20 a magnetic needle supported over a pivot made upto hard steel. Compass surveying chain surveying can be used when the area to be surveyed is comparatively small and is fairly flat. There are two methods to using a military compass, the center hold technique or the more accurate compass tocheek technique. A small button in the rear of the compass activates a needle freeze mechanism to hold a compass heading for easier reading. It contains a prism which is used for accurate measurement of readings. It is a round plastic container filled with liquid and has the compass needle inside. The base forms the body of the compass and holds the needle, dial and rotating scales.
Angular measurements refer to the magnetic bearing or horizontal angle taken by a prismatic compass or theodolite. Take your lensatic compass and open it up all the way so it is one flat line. Usually, a diagram called a compass rose shows the directions north, south, east, and west on the compass face as abbreviated initials. Compass surveying principles use of prismatic compass, measurement of bearings, conversion of bearings, local attraction, correction of compass traverse.
The booklet can be used by all ranks of hm forces rn, rm, army and raf for study and revision. A typical lensatic compass is shown at the right from fm 2125. With 41 illustrations, plates and diagrams dei riaz, paul on. The prismatic compass and how to use it 1917 compass library. When the magnetic needle is suspended freely and balanced properly. War department technical manual ordnance maintenance prismatic compass, m1918 july 17, 1941. The prismatic compass and how to use it a pocket manual on military prismatic compasses revised and enlarged by major a. The prismatic attachment consists of a 45 reflecting prism with the eye and reading faces made slightly convex so as to magnify the image of the graduations. The compass body is constructed mainly from brass and incorporates a bellows expansion system to allow for volumetric changes in the damping fluid contained within the capsule. Aug 21, 2017 how to drawing a prismatic compass prismatic compass part. A prismatic compass is a navigation and surveying instrument which is extensively used to find out the bearing of the traversing and included.
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