Section 117 Flashcards
What are the 12 parts of the lensatic compass?
- Luminous Sighting Dots
- Sighting Wire
- Luminous Magnetic Arrow
- Short Luminous Line
- Fixed Index Line
- Graduated Straight Edge
- Sighting Slot
- Lens
- Thumb Loop
- Floating Dial
- Bezel Ring
- Lens or Rear Sight
Discuss the map feature identified by RED.
Classifies cultural features, such as populated areas, main roads, and boundaries, on older maps.
Discuss the map feature identified by BLUE
Identifies hydrography or water features such as lakes, swamps, rivers or drainage.
Discuss the map feature identified by RED BROWN.
Red and brown combined on red-light readable maps to identify cultural features, all relief features, non-surveyed spot elevations, and elevations such as contour lines.
Discuss the map feature identified by BLACK
Indicated cultural (man-made) features such as buildings and roads
Discuss the map feature identified by BROWN.
Identifies all relief features and elevations, such as contours on older edition maps, and cultivated land on red-light readable maps.
Discuss the map features using a standard 1:50,000 military map: HILL
Hill is an area of high ground. Hill is shown on a map by contour lines forming concentric circles. Inside of the smallest closed circle is the hilltop.
Discuss the map features using a standard 1:50,000 military map: SADDLE
Saddle is a dip or low point between two areas of higher ground. May be a dip/break along a level ridge crest. A saddle is normally represented as an hourglass.
Discuss the map features using a standard 1:50,000 military map: RIDGE
Ridge is sloping line of high ground. Standing on a ridge you will have low ground in 3 directions and high ground in 1. Contour lines forming a ridge tend to be C-Shaped or V-Shaped. Closed end of the contour line points away from high ground
Discuss the map features using a standard 1:50,000 military map: DEPRESSION
A low point in the ground or sinkhole. It could be described as an area of low ground surrounded by higher ground in all directions. Represented by closed contour lines that have tick marks pointing toward low ground.
Discuss the map features using a standard 1:50,000 military map: FINGER (SPUR)
Spur is a short, continuous sloping line of higher ground, normally jutting out from the side of a ridge. A spur is often formed by two rough parallel streams, which cut draws down the side of a ridge.
Discuss the map features using a standard 1:50,000 military map: DRAW
Draw is a less developed stream course than a valley. If you are standing in a draw, the ground slopes upward in 3 directions and downward in the other. Draw could be considered as the initial formation of a valley. The contour lines depicting a draw are U-Shaped or V-Shaped, pointing toward high ground.
Explain what a grid azimuth is.
When and azimuth is plotted on a map between point A (starting point) and point B (ending point). Points are joined together by a straight line. Protractor is used to determine angle between grid North and drawn line.
Explain what a magnetic azimuth is.
Determined by using magnetic instruments, such as lensatic and M2 compass.
Explain what a back azimuth is.
The opposite direction of an azimuth. It is comparable to doing “about face” To obtain a back azimuth from an azimuth, add 180 degrees if the azimuth is 180. The back azimuth of 180 can be stated as 0 or 360.
Discuss or show True North.
A line from any point on the earth’s surface to the North Pole. All lines of longitude are true north lines. True north is usually represented by a star.
Discuss or show magnetic north.
Direction to the north magnetic pole, as indicated by the north-seeking needle of a magnetic instrument. The magnetic north is usually symbolized by a line ending with half of an arrowhead. Magnetic readings are obtained with magnetic instruments
Discuss or show Grid North.
North that is established by using he vertical grid lines on the map. Grid north may be symbolized by the letters GN or the letter “y”
Discuss the techniques used to orient a map using a Compass.
Compass measures magnetic north. With map in horizontal position, take the straightedge on the left side of the compass and place it along the magnetic north arrow on the declination diagram with the cover of the compass pointing toward the top of the map. This procedure places the fixed black index line of the compass parallel to the magnetic north arrow. Keeping the compass aligned as directed, rotate the map and compass together until the arrows line up.
Discuss the techniques used to orient a map using Terrain Association.
Use this method when a compass is unavailable. Identify prominent terrain features on the map that you can find on the ground. Align terrain features with the map. If there is a tower to your front, then orient the map so that the tower is to your right front. If there is a road to your left, ensure the road on the map is parallel. Once all features are lined up, your map is oriented.
Discuss the procedure for determining the location of an unknown point by intersection.
Intersection is the location of an unknown point by successfully occupying at least two or three known positions on the ground and then map sighting on the unknown location. It is used to locate distant or inaccessible points or objects such as enemy targets and danger areas. There are two methods of intersections: The map and compass method The straightedge method.
