This graphic is the Grid and Magnetic North Declination Arrow. The vertical black line with the star at the top is the True North indicator. This line points towards Geographic or "True" North.

The blue G arrow indicates the Grid declination. This is the amount the UTM grid differs from geographic North at this location. Since all USGS maps use the Universal Transverse Mercator (UTM) projection, this line indicates "straight up" on the UTM map - it's a line of constant Easting value on the map. The blue value below the map, labeled "G =" is the value of the Grid declination in degrees. The blue arrow points in the direction of UTM Grid North.

The red M arrow indicates the Magnetic declination. This is the amount True North differs from magnetic North at this location right now. The red value below the map, labeled "M =" is the value of the Magnetic declination in degrees. The red arrow points in the direction of magnetic North. The Magnetic North Pole is constantly moving, and the Magnetic declination shown here was the correct value of the declination as of 12/23/2005. If you compare this value to the declination shown on a printed topographic map you may find a significant difference between the two, because the declination on the printed map was calculated when the map was printed, not as of 12/23/2005.