increases north, if you are in the southern hemisphere the northing of the equator is 10,000,000 meters and decreases south.  See Figure 3-18.  Grid lines which run north and south are easting lines; these lines are parallel to the central meridian of the grid zone.  Grid lines which run east and west are northing lines; these lines are parallel to the equator.    6° 84° N 80° S EQUATOR 0mN 1,000,000mN 2,000,000mN 3,000,000mN 4,000,000mN 5,000,000mN 6,000,000mN 4,000,000mN 5,000,000mN 6,000,000mN 7,000,000mN 8,000,000mN 9,000,000mN 10,000,000mN NOT TO SCALE Figure 3-18   UTM Easting and Northing d.  Grid Convergence.       1.  Grid convergence at a point in the UTM system is the angle measured east or west from true north to grid north.  See Figure 3-19.  At any point along the central meridian of a UTM grid zone, true north and grid north are the same.  At any point not located on the central meridian, grid north departs from true north because of convergence of the meridians.  Grid convergence within the UTM system is a function of both latitude and longitude.  It will rarely exceed 3° (53.333 mils) and is normally listed in the declination diagram of a map.  Grid convergence should be computed for use in 5th order or higher surveys because the information on the map is generally computed for the center of the mapsheet.  For example, the Lawton mapsheet (6353III) lists the grid convergence at 6 mils, the Cache mapsheet (6253II) lists it at 4 mils; there are two mils difference between the centers of these two adjoining sheets (approximately 23 km).                    GRID CONVERGENCE GN GN GN GN GN GN GN SOUTH POLE NORTH POLE GN = TN Figure 3-19   UTM Grid Convergence     2.  In the northern hemisphere, grid convergence is considered negative east of the central meridian and positive west.  In the southern hemisphere, grid convergence is considered to be positive east of the central meridian and negative west.  See Figure 3-20. The direction (+,-) and the value of the grid convergence is applied to a true azimuth to obtain a grid azimuth. If a grid azimuth must be converted to a true azimuth, the value of the grid convergence is the same; however, the opposite sign (direction) must be used. DRAFT 3-30 EQUATOR + + Figure 3-20  Sign of Grid Convergence