![]() There are variants of this design including a universal precision protractor and a precision universal Vernier protractor with a more technical design. The construction of a bevel protractor consists of a beam, a graduated dial and a blade which is connected to a swivel plate by a thumb nut and clamp. The Vernier scale is found underneath the main degree scale and is spaced so it reads at a constant fraction of the fixed main scale.Bevel Protractors:These are able to measure through 360° by using one or two swinging arms that can help measure the angle. In the Vernier scale, each graduation represents 0.02 mm or 1/12 of a degree. This type of protractor is commonly used in classrooms for geometry and in mechanical and engineering-related applications.The Vernier Scale:This is used on protractors to enable them to give more precise and accurate measurements. The semi-circular protractor is used for reading, drawing and plotting angles on paper or charts. On the base of the protractor is a midpoint mark that indicates the position of the highest point of the angle that is going to be measured or the vertex. More durable and typically higher quality protractors can be made of metals such as aluminium or Stainless Steel.Types of ProtractorSemi-Circular Protractor:This protractor has two sets of scales graduated up to 180° in opposite directions enabling angles to be read from two directions. If the two counts are equal, the protractor is properly aligned.Protractors A protractor is a mathematical instrument often made from clear plastic used for measuring angles in degrees such as the angles of a triangle or a hexagon. Count the number of degrees from the 0-degree mark at the top of the protractor to this north-south grid line and then count the number of degrees from the 180-degree mark at the bottom of the protractor to this same grid line. (3) Note that the protractor is cut at both the top and bottom by the same north-south grid line. (2) The user should re-read the azimuth between the azimuth and north-south grid line to check the initial azimuth. The user should be able to determine whether the initial azimuth reading was correct. (1) Place the protractor index where the azimuth line cuts a north-south grid line, aligning the base line of the protractor directly over the intersection of the azimuth line with the north-south grid line. ![]() To obtain an accurate reading with the protractor (to the nearest degree or 10 mils), there are two techniques to check that the base line of the protractor is parallel to a north-south grid line. Distance does not change an accurately measured azimuth.įigure 6-7. ![]() When measuring an azimuth, the reading is always to the nearest degree or 10 mils. This is the grid direction line (azimuth). (d) Remove the protractor and draw a line connecting the known point and the mark on the map. (c) Make a mark on the map at the desired azimuth. (b) Place the protractor on the map with the index mark at the center of mass of the known point and the base line parallel to a north-south grid line. (a) Convert the azimuth from magnetic to grid, if necessary. (2) To plot an azimuth from a known point on a map ( Figure 6-7). (d) Read the value of the angle from the scale this is the grid azimuth from point A to point B ( Figure 6-4). (c) Keeping the index at this point, align the 0- to 180-degree line of the protractor on the vertical grid line. (b) Place the index of the protractor at the point where the drawn line crosses a vertical (north-south) grid line. (a) Draw a line connecting the two points (A and B). The 0- or 360-degree mark is always toward the top or north on the map and the 90° When using the protractor, the base line is always oriented parallel to a north-south grid line. ![]() Where the base line intersects the horizontal line, between 90 and 270 degrees, is the index or center of the protractor ( Figure 6-6).ī. A line from 0 to 180 degrees is called the base line of the protractor. The degree scale is graduated from 0 to 360 degrees each tick mark on the degree scale represents one degree. This protractor represents the azimuth circle. The military protractor, GTA 5-2-12, contains two scales: one in degrees (inner scale) and one in mils (outer scale). The index mark is the center of the protractor circle from which all directions are measured.Ī. All of them divide the circle into units of angular measure, and each has a scale around the outer edge and an index mark. There are several types of protractors-full circle, half circle, square, and rectangular ( Figure 6-5). ![]() Precision lightweight global positioning system receiver Navigation in different types of terrainĬ. SurvivalIQ Handbook: Land Navigation - Direction - Protractorġ3. ![]()
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