2.  If at any time you cross the equator from north to south (at which point you would have a negative northing), you must algebraically add the northing to ten million meters to obtain a northing for the southern hemisphere.  If you cross the equator from south to north (which would produce a northing greater than ten million meters), you must subtract ten million meters from your northing to obtain a northing which can be used in the northern hemisphere. 3-17  Universal Polar Stereographic Grid a.  The Universal Polar Stereographic (UPS) Grid System is referenced to the Polar Stereographic Projection.  It is used to map the polar regions of the earth north of 84° N latitude and south of 80° S latitude.   b.  Each polar region is a grid zone.  The two zones are not numbered as in the UTM system, they are merely referred to as the North and South grid zone.  See Figure 3-17.  The origin for each UPS grid zone is the pole (North or South).  The grid is oriented by placing the east-west axis of the grid in coincidence with the 90°W and 90°E meridians and the north-south axis of the grid in coincidence with the 0° and 180° meridians. c.  The location of any point on a UPS grid can be designated by coordinates by giving its distance east-west (easting) of the 0° and 180° meridians or north-south (northing) of the 90°W and 90°E meridians.  A value of 2,000,000 meters is assigned to the meridians for both easting and northing.  The easting value increases from two million meters toward the eastern hemisphere and decreases toward the western hemisphere in both grid zones.  The northing value in the North grid zone increases from two million meters in the direction of the International Dateline (180° longitude) and decreases in the direction of the Prime Meridian (0° longitude).  In the South grid zone, the northing value increases from two million meters in the direction of the Prime Meridian and decreases in the direction of the International Dateline.  See Figure 3-22.   d.  Grid Convergence.       1.  In the North zone, grid north is the direction toward the North Pole along the 0° meridian and the direction away from the North Pole along the 180° meridian.  In the South zone, grid north is the direction toward the South Pole along the 180° meridian and the direction away from the South Pole along the 0° meridian.  For any points not on the 0° and 180° meridians, grid north is the northern direction of a line through the point which is parallel to those meridians.       2.  All meridians of longitude are straight lines radiating from the center of the grid (North and South zone).  These lines are true north-south lines; therefore, the direction of true north at a point is the same as the longitude at that point.     3.  As with the UTM system, grid convergence is the angle from a true north line to a grid north line. Grid north is the same as true north along the 0° meridian.  Grid north is in the opposite direction of true north along the 180° meridian.  Grid convergence increases east and west of 0° to 180°.  The value of grid convergence at any point in the UPS system is equal to the longitude of that point and is expressed as an angular measure east or west as measured from true north.  See Figure 3-23. 80° SOUTH POLE 0° 180° 90° E 90° W SOUTH ZONE 84° NORTH POLE 0° 180° 90° E 90° W NORTH ZONE 40° E GN TN 130° E GN TN GRID CONVERGENCE 40° E GRID CONVERGENCE 130° W Figure 3-23   UPS Grid Convergence e.  UPS Grid Coordinates.  In the UPS grid system, both eastings and northings will consist of seven digits DRAFT 3-19