117. Land Navigation Flashcards
What is the purpose of a declination diagram?
It gives information needed to convert grid azimuth (on the map) to magnetic azimuth (for your compass).
An eight digit map grid position will locate you down to:
10 meters
The map grid position (location) in a SALUTE report should be how many digits at a minimum?
6 digits
What is true north?
A line on 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 on the map.
What is grid north?
The north that is established by using the vertical grid lines on your map. Grid north may be symbolized by the letters GN or the letter Y. It is often parallel to true north.
What is a back azimuth?
Back Azimuth. A back azimuth is the opposite direction of an azimuth. To obtain a back azimuth from an azimuth, add 180 degrees if the azimuth is 180 degrees or less, or subtract 180 degrees if the azimuth is 180degrees or more. The back azimuth of 180 degrees may be stated as 0degrees or 360 degrees. For mils, if the azimuth is less than 3200mils, add 3200 mils, if the azimuth is more than 3200 mils, subtract 3200 miles.
What is a grid azimuth?
Grid Azimuth. When an azimuth is plotted on a map between point A (starting point) and point B (ending point), the points are joined together by a straight line. A protractor is used to measure the angle between grid north and the drawn line, and this measured azimuth is the grid azimuth.
Discuss the procedure for determining the location of an unknown point by intersection.
Orient the map using the compass.
Locate and mark your position on the map,
Determine the magnetic azimuth to the unknown position using the compass.
Convert the magnetic azimuth to grid azimuth.
Draw a line on the map from your position on this grid azimuth.
Move to a second known point and repeat steps 1, 2, 3, 4, and 5.
The location of the unknown position is where the lines cross on the map. Determine the grid coordinates to the desired accuracy.
Discuss the procedures for determining a location by resection.
Orient the map using the compass.
Identify two or three known distant locations on the ground and mark them on the map.
Measure the magnetic azimuth to one of the known positions from your location using a compass.
Convert the magnetic azimuth to a grid azimuth.
Convert the grid azimuth to a back azimuth. Using a protractor, draw a line for the back azimuth on the map from the known position back toward your unknown position.
Repeat for a second position and a third position.
The intersection of the lines is your location. Determine the grid coordinates to the desired accuracy.
Describe the map features identified by the following color:
Red
Red Classifies cultural (manmade) features, such as populated areas, main roads, and boundaries, on older maps.
Describe the map features identified by the following color:
Blue
Blue Identifies hydrography or water features such as lakes, swamps, rivers, and drainage.
Describe the map features identified by the following color:
Black
Black Indicates cultural (man-made) features such as buildings and roads, surveyed spot elevations, and all labels.
Describe the map features identified by the following color:
Brown
Brown Identifies all relief features and elevation, such as contours on older edition maps, and cultivated land on red-light readable maps.
Describe the map features identified by the following color:
Red Brown
The colors red and brown are combined on red-light readable maps to identify cultural features, all relief features, non-surveyed spot elevations, and elevations such as contour lines.
Describe the map features identified by the following color:
Green
Green Identifies vegetation with military significance such as woods, orchards, and vineyards.
