NAD 27 and NAD 83 are two different systems used to calculate coordinates. NAD 27 is the older coordinate system, while NAD 83 is the more current system. The two systems use different algorithms to calculate coordinates, so it is important to know which system your data uses before comparing or converting coordinates. While both systems are widely used in North America, NAD 83 is gradually becoming more popular worldwide.
What is NAD 27?
NAD 27 is the surveying and mapping datum for North America. It was adopted in 1927 and remained in use until 1986 when it was replaced by NAD 83. NAD 27 is based on the Clarke 1866 ellipsoid, which was slightly different from the World Geodetic System of 1984 (WGS 84), the current standard. As a result, NAD 27 positions are no longer accurate, and maps using NAD 27 data should be updated. NAD 27 is still used in some parts of the world, particularly in Mexico and Central America. In these regions, NAD 27 is often referred to as “Old NAD.”
What is NAD 83?
NAD 83 is a horizontal control datum for mapping and surveying the United States and its possessions. NAD 83 was established in 1986 as a revision of NAD 27, which had been in use since 1927. NAD 83 is based on a network of approximately 250 GPS stations nationwide and can be adjusted to better match local conditions. NAD 83 is the most commonly used datum in North America and is also used in many other countries for their own mapping and surveying needs.
Difference between NAD 27 and NAD 83
NAD 27 and NAD 83 are two different systems used for measuring geographic locations. NAD 27 is based on the Clarke Ellipsoid of 1866, while NAD 83 is based on the GRS 80 ellipsoid. As a result, NAD 27 is slightly larger than NAD 83. NAD 27 is also more centered on the Earth’s crust, while NAD 83 takes into account the Earth’s molten core. In addition, NAD 27 uses the foot as its unit of measure, while NAD 83 uses the meter. Finally, NAD 27 is not compatible with GPS systems, while NAD 83 is. As a result, when working with geographic locations, it is important to identify which system is being used.
Conclusion
The NAD 27 and NAD 83 coordinate systems are both used in surveying, but they use different data. A datum is a reference point for measuring locations on Earth. The NAD 27 coordinate system uses the North American Datum of 1927, while the NAD 83 coordinate system uses the North American Datum of 1983. Each has its strengths and weaknesses, so it’s important to understand which one your project will use.
