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Land Nav Task 9 - Convert Azimuths

Standards: Converted the given magnetic azimuth to a grid azimuth and the given grid azimuth to a magnetic azimuth without error.

Conditions: Given a standard 1:50,00-scale military map with a declination diagram, a pencil, and a magnetic azimuth and a grid azimuth that must be converted.

Standards: Converted the given magnetic azimuth to a grid azimuth and the given grid azimuth to a magnetic azimuth without error.

 

Performance Steps

1.   The north-south lines on your map give grid north. The needle of your compass points to magnetic north. Grid north and magnetic north are usually different by a few degrees. Neither one points straight to the North Pole (called true north), but you do not need to know true north to keep from getting lost in a combat area. The difference in degrees for every map is shown on the bottom of mapsheet (figure C-30).


Figure C-30. Declination diagram


2.   The difference between grid north and magnetic north is called the grid-magnetic (G-M) angle. The diagram at the bottom of the map tells you how to change grid azimuths to magnetic azimuths and magnetic azimuths to grid azimuths (figure C-31).


Figure C-31. G-M angle

 

3.   For example, you aim your compass at a distant point. The compass reading you get is 190 degrees, the magnetic azimuth. The diagram on your map (see figure 2) tells you that the G-M angle is 9 degrees, and it also tell you that "to convert a magnetic azimuth to a grid azimuth, add the G-M angle." Therefore add 9 degrees to your compass reading. This gives you 190 + 9 = 199. Your grid azimuth is 199 degrees.

4.   The G-M angle depends on where you are in the world.

5.   Convert azimuths when given an easterly G-M angle (figure C-32).


Figure C-32. Converting azimuths with easterly G-M angle


a. To convert a magnetic azimuth to a grid azimuth, add the value of the G-M angle to the magnetic azimuth.

b. To convert a grid azimuth to a magnetic azimuth, subtract the G-M angle from the grid azimuth.

6.   Convert azimuths when given a westerly G-M angle (figure C-33).


Figure C-33. Converting azimuths with westerly G-M angle


a. To convert a magnetic azimuth to a grid azimuth, subtract the value of the G-M angle from the magnetic azimuths.

b. To convert a grid azimuth to a magnetic azimuth, add the value of the G-M angle to the grid azimuth.

Evaluation Preparation: 

Setup: Give the soldier a standard 1:50,000-scale military map, a piece of paper, a pencil, and a magnetic and grid azimuth to be converted.

Brief Soldier: Tell the soldier to convert the magnetic azimuth to a grid azimuth and the grid azimuth to a magnetic azimuth.

Performance Measures

GO

NO GO

1.   Determined correct grid azimuth.

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2.   Determined correct magnetic azimuth.

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Evaluation Guidance:  Score the soldier GO if all performance measures are passed. Score the soldier NO GO if any performance measure is failed. If the soldier scores NO GO, show what was done wrong and how to do it correctly.

References

 

Required

Related

 

FM 3-25.26