Based on its findings, a standard based on the MGRS was adopted and brought to the Federal Geographic Data Committee (FGDC) in 1998. After an iterative review process and public comment period, the USNG was adopted by the FGDC as standard FGDC-STD-011-2001 in December 2001. Since then, the USNG has seen gradual but steadily increasing adoption both in formal standards and in practical use and applications, in public safety and in other fields. Users encountering the USNG (or similar grid reference systems) sometimes question why they are used instead of latitude and longitude coordinates, with which they may be more familiar. Proponents note that, in contrast to latitude and longitude coordinates, the USNG provides:   This format ambiguity has led to confusion with potentially serious consequences, particularly in emergency situations. All of the above also lead to USNG references being typically very succinct and compact, with flexibility to convey precise location information in a short sequence of characters that is easily relayed in writing or by voice. As with any projection that seeks to represent the curved Earth as a flat surface, distortions and tradeoffs will inevitably occur. The USNG attempts to balance and minimize these, consistent with making the grid as useful as possible for its intended purpose of efficiently communicating practical locations. Since the UTM (the basis for USNG) is not a single projection, but rather a set of 6-degree longitudinal zones, there will necessarily be a local discontinuity along each of the 'seam' meridians between zones. However, every point continues to have a well-defined, unique geoaddress, and there are established conventions to minimize confusion near zone intersections. The six-degree zone width of UTM strikes a balance between the frequency of these discontinuities versus distortion of scale, which would increase unacceptably if the zones were made wider. (UTM further uses a 0.9996 scale factor at the central meridian, growing to 1.0000 at two meridians offset from the center, and increasing toward the zone boundaries, so as to minimize the overall effect of scale distortion across the zone breadth.) The USNG is not intended for surveying, for which a higher-precision (lower-distortion) coordinate system such as SPCS would be more appropriate. Also, since USNG north-south grid lines are (by design) a fixed distance from the zone central meridian, only the central meridian itself will be aligned with "true north". Other grid lines establish a local "grid north", which will differ from true north by a small amount.