Which method is used to convert grid azimuth to magnetic azimuth in the system described?

Which method is used to convert grid azimuth to magnetic azimuth in the system described?

• A. Direct bearing method
• B. Declination diagram method
• C. Left Add/Right Subtract (LARS) method
• D. Compass alignment method

Answer: (C)

Converting grid azimuth to magnetic azimuth hinges on applying the magnetic declination between grid north and magnetic north. The Left Add/Right Subtract method is the practical rule you use: if the magnetic north lies to the left of grid north (west declination), add the declination to the grid azimuth; if it lies to the right (east declination), subtract the declination. For example, with a grid azimuth of 60 degrees: - West declination of 12 degrees → magnetic azimuth is 72 degrees (60 + 12). - East declination of 12 degrees → magnetic azimuth is 48 degrees (60 − 12). This method is preferred for quick field conversions because it directly encodes how the compass reading compares to the map grid, whereas other methods provide ways to determine the declination or align the instrument but don’t offer the same straightforward conversion rule.

Converting grid azimuth to magnetic azimuth hinges on applying the magnetic declination between grid north and magnetic north. The Left Add/Right Subtract method is the practical rule you use: if the magnetic north lies to the left of grid north (west declination), add the declination to the grid azimuth; if it lies to the right (east declination), subtract the declination.

For example, with a grid azimuth of 60 degrees:

• West declination of 12 degrees → magnetic azimuth is 72 degrees (60 + 12).

• East declination of 12 degrees → magnetic azimuth is 48 degrees (60 − 12).

This method is preferred for quick field conversions because it directly encodes how the compass reading compares to the map grid, whereas other methods provide ways to determine the declination or align the instrument but don’t offer the same straightforward conversion rule.