It has been revised several times since then. This request developed into the State Plane Coordinate System (SPCS), which is now the most widely used expression of coordinate information in local and regional surveying and mapping applications in the United States and its territories. In 1933, the North Carolina Department of Transportation asked the Coast and Geodetic Survey to assist in creating a comprehensive method for converting curvilinear coordinates (latitude and longitude) to a user-friendly, 2-dimensional Cartesian coordinate system. The panhandle of Alaska, whose maximum dimension is on a diagonal, uses an Oblique Mercator projection, which minimizes the combined error in the X and Y directions. Zones that are long in the north–south direction use the transverse Mercator projection because it is better at maintaining accuracy along a north–south axis, due to the circumference of the projection cylinder being oriented along a meridian of longitude. These zones use the Lambert conformal conic projection, because it is good at maintaining accuracy along an east–west axis, due to the projection cone intersecting the earth's surface along two lines of latitude. States that are long in the east–west direction are typically divided into zones that are also long east–west. The choice between the two map projections is based on the shape of the state and its zones. Most state plane zones are based on either a transverse Mercator projection or a Lambert conformal conic projection. Outside a specific state plane zone accuracy rapidly declines, thus the system is not useful for regional or national mapping. Second, the system is highly accurate within each zone (error less than 1:10,000). By using the Cartesian coordinate system's simple XY coordinates, "plane surveying" methods can be used, speeding up and simplifying calculations. First, it uses a simple Cartesian coordinate system to specify locations rather than a more complex spherical coordinate system (the geographic coordinate system of latitude and longitude). Its popularity is due to at least two factors. The system is widely used for geographic data by state and local governments. There are 110 zones in the contiguous US, with 10 more in Alaska, 5 in Hawaii, and one for Puerto Rico and US Virgin Islands. Each state contains one or more state plane zones, the boundaries of which usually follow county lines. The State Plane Coordinate System ( SPCS) is a set of 124 geographic zones or coordinate systems designed for specific regions of the United States. ( November 2012) ( Learn how and when to remove this template message) Please help to improve this article by introducing more precise citations. This article includes a list of references, related reading or external links, but its sources remain unclear because it lacks inline citations.