Latitude-longitude is not a two-dimensional coordinate system but is commonly referred to as one. Lines of latitude run east west parallel to the equator. Longitude lines run north-south and converge at the poles. Therefore, the length of one degree of longitude varies depending upon the latitude at which it is measured. For example, one degree of longitude at the equator is 111 kilometers in length, but the length of one degree of longitude converges to zero at the poles. Latitude-longitude is measured in degrees, minutes, and seconds, and because degrees aren’t associated with a standard length, they can’t be used as an accurate measure of distance or area. A common coordinate in latitude-longitude for South Carolina is 82.2 degrees west latitude and 34.2 degrees north longitude. In this example, the minutes and seconds are shown as decimals of one degree (i.e., decimal degrees). A great deal of commercially available data is packaged in latitude-longitude because it is by definition, not projected That way, the user can project it to whatever projection they are working in.