Based on Clarke Ellipsoid that involved the manual survey of the entire continent, NAD 27 is the official datum system that is commonly used in North America. The system is used by cartographers and satellite navigation system for the purpose of translating position of their object to their actual and real position on Earth. NAD 27 is based on longitude and latitude, as well as the direction between two points. It involved the horizontal control datum for America. Since NAD 27 is a manual surveying system of the entire continent, it is still dependant on traditional positioning technology. As it does not support the contemporary positioning technology, it is often said to be a somewhat obsolete system and is being replaced by newer system, which give better results. It is not known if any efforts are being made to make the system compatible to the newer technology that is currently available.
- Image Courtesy: dmap.co.uk
NAD 83 is also a geodetic system, which is prevalent in America. Its foundation is based on the Geodetic Reference System (GRS), created in 1980, which involved dealing with the approximate measure of the planet as a whole. Unlike other datum, it dealt with the horizontal control for the three North American countries, namely America, Canada and Mexico, as well as Central America. Since NAD 83 is an earth-centered datum, it has no direction or initial point. It has the capability of supporting three-dimensional capabilities of modern positioning technology and consequently ends up being a far more accurate than other datum systems. The system makes significant contributions in the field of space science.
- Image Courtesy: ccma.nos.noaa.gov