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Archive for the ‘Location By Grid Coordinates’ Category
Angular Measurement!
In Both Mils and Degrees
A thorough understanding of Angular Measurement and its components are sometimes critical to determining the correct Declination Constant data. This data is normally measured in degrees or mils, and is what you will either add or subtract from the base Direction/Azimuth to change it from grid to magnetic or magnetic to grid.
a. Degree: Most common unit of measurement and normally expressed as (o). Its subdivisions are minutes (‘) and seconds (“):
- 1 degree = 60 minutes;
- 1 minute = 60 seconds.
b. Mil: Normally expressed as mils or Mils. Most compasses and map protractors have scales in both mils and degrees. There are 6400 mils in a circle as compared with 360 degrees. The conversion ratio is 17.78 mils to 1 degree.
If accuracy is of utmost importance, the smaller form of angular measurement should be used. Knowing is not enough, you must have a quality map, a good compass, protractor, and a sharp pencil.
Location by Grid Coordinates!
Location by Grid Coordinates
In a city, it is quite simple to find a location. The streets are named and the buildings have numbers; but, in undeveloped areas, it’s not so simple. There is a method/process for determining and reporting positions or locations using a topographical map.
Superimposed on each Topographical Map are a series of numbered North-South (N-S) and East-West (E-W) grid lines. Where these N-S and E-W grid lines intersect forms a grid square. Each grid square is numbered using the applicable N-S and E-W grid line numbers. Each grid square is 1,000×1,000 meters.
As depicted in the diagram above, the key to determining the grid coordinates for a position/point on a map is to read right and up. Starting in bottom right corner of the map – read right to the N-S grid line closest (but still left) of the marked position (14); then estimate the distance in tenths (0-9) that the position is to the right of the identified N-S grid line (2); next, read up to the E-W grid line closest but still at the bottom of the marked position (84); next, estimate the distance in tenths (0-9) that the position is up from the identified E-W grid line (7). The grid coordinates to the position you have identified are: 142847. The US Military uses this Map Reading method/procedure extensively to identify locations on Topographical Maps.
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