(New York, 1936), 203 Catalogue of Keuffel & Esser, 39th ed. (New York, 1921), 119 Catalogue of Keuffel & Esser, 38th ed. (New York, 1916), 172 Catalogue of Keuffel & Esser, 36th ed. (New York, 1913), 172 Catalogue of Keuffel & Esser, 35th ed. Cooke, "Scales for Determining Slope from Topographic Maps," The Professional Geographer 20, no. K&E noted in the 1943 catalog that the changed form was manufactured according to the specifications of the Corps of Engineers. The design of the instrument changed again between 19. K&E began to sell this form of military protractor between 19, so this object may have been in use during World War I (as the markings suggest). Army Corps of Engineers in the 19th and 20th centuries. The United States Engineering Department was part of the U.S. Maker's and owner's marks are near the lower edge: KEUFFEL & ESSER CO. The first is marked by thousands of yards from 1,000 to 8,000 the second is marked by 500 yards from 500 to 2,500 and the third is marked by 500 yards from 500 to 1,000. Each scale is divided in 100-yard increments. Below that scale are three scales for 1", 3", and 6" to the mile, respectively. The scales for each set of slope measurements are not indicated, but they presumably are standard scales for American military engineering, such as 1:63,360 and 1:25,000.Ī scale of inches divided to tenths and marked by ones from 0" to 5" appears on the interior of the protractor. These allow draftsmen to read or draw topographical contours indicating slopes in landforms of 7° and 3-1/2° 8°, 4°, 2°, and 1° 10°, 5°, and 2-1/2° and 12°, 6°, 3°, and 1-1/2°, respectively. A small hole near the 160° mark permits a weight to be suspended so that the protractor functions as a rough clinometer, to measure angles of elevation or slope.įour slope scales appear on the bottom edge of the instrument. It is divided by degree and marked by tens from 10° to 170° and from 190° to 350°, both in the clockwise direction. Or something that is bigger than the hole in the tool.Īdditional techniques for plotting a bearing.This yellow xylonite (celluloid-like plastic) rectangular protractor is contained in a paper wrapper marked: MILITARY PROTRACTOR (/) MADE BY (/) KEUFFEL & ESSER CO. If your string is too short to make a loop, tie the end to a small twig, a button, Some folks like red thread, others prefer black, and some want a loop of thin elastic cord. Sewing kit, a thread from the core of a piece of para-cord, dental floss. Some field expedient string sources include, thread from a Line it up with the bearing on the edge of the protractor, and use the straight lineĬreated by the thread to follow the bearing away from the edge of the protractor. Longer that twice the distance you might want to extend a bearing.) Pull the string tight, String through the center hole and tie the ends together. Tools with protractors have a hole in the center. This is what we demonstrated in the above example.Īnother technique is to use a piece of thread to show your bearing line. Draw a line between these two points, and extend it asįar as you need to. Now place a straight edge between the known point and the mark you One of simplest techniques is to place a small pencil mark on the correct bearing at theĮdge of the protractor. Techniques for extending the bearing line The center of your protractor will be at the intersection of a line drawn between 0° and 180° and a line between 90° and 270°ĭetermine what lines to use to align your protractor with your north reference lines on your map.Ī protractor that is well suited for navigation will have numerous parallel lines aligned with 0° to 180° on the protractor. You will place the center of the protractor on the known point where you are plotting your bearing. Some protractors are numbered in four 90° quadrants,Īnd are a probably not a good choice for navigation use.įind the center point for your protractor. Make sure you use the correct set of numbers. You proceed in a clockwise direction? Many protractors used for drafting are numbered in both clockwise and counterclockwise directions. Is you protractor marked in degrees? Are the marks spaced at one, two, or five degrees? Is it a full or half circle protractor. 0° (and 360°)Īre aligned with our north reference, 90° is to the East, 180° to the South, and 270° to the West. Familiarize yourself with your protractorīefore you set you protractor down onto the map, take a good look at it and make sure you understand the markings.įor navigation purposes, we use an angular measurement system where a circle is divided into 360 degrees.
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