To convert a grid azimuth to a magnetic azimuth, you should

To convert a grid azimuth to a magnetic azimuth, you should

• A. Subtract GM angle
• B. Add GM angle
• C. Multiply GM angle
• D. Divide GM angle

Answer: (A)

When converting a grid azimuth to a magnetic azimuth, you subtract the GM angle because the GM angle represents how far magnetic north is from grid north (GM angle = grid north minus magnetic north). To shift the reference from grid north to magnetic north, you remove that difference: magnetic azimuth = grid azimuth − GM angle. For example, if the grid azimuth is 60 degrees and the GM angle is 10 degrees, the magnetic azimuth is 50 degrees. If the GM angle were negative (magnetic north east of grid north), subtracting a negative would increase the grid value, so magnetic azimuth would be grid azimuth plus that absolute GM value. In short, you’re moving from the grid reference to the magnetic reference by subtracting the GM angle.

When converting a grid azimuth to a magnetic azimuth, you subtract the GM angle because the GM angle represents how far magnetic north is from grid north (GM angle = grid north minus magnetic north). To shift the reference from grid north to magnetic north, you remove that difference: magnetic azimuth = grid azimuth − GM angle.

For example, if the grid azimuth is 60 degrees and the GM angle is 10 degrees, the magnetic azimuth is 50 degrees. If the GM angle were negative (magnetic north east of grid north), subtracting a negative would increase the grid value, so magnetic azimuth would be grid azimuth plus that absolute GM value. In short, you’re moving from the grid reference to the magnetic reference by subtracting the GM angle.