Canada
NAD 27 vs NAD 83
The North American Datum, or NAD, is the official geodetic datum that is prevalent in North America. There are two kinds of datum used in North America, namely, the North American Datum of 1927 (NAD 27) and the North American Datum of 1983 (NAD 83).
Although the NAD 27 and NAD 83 are both geodetic systems, each one of them is based on different measurements. When considering their measurement, the North American Datum 27 was based on Clarke Ellipsoid, which dealt with the manual surveying of the whole continent. The foundation of the North American Datum 83 was based on the Geodetic Reference System (GRS) of 1980, which dealt with the approximate measurement of the earth as a whole.
The NAD 27 dealt with the horizontal control datum for the US, and the NAD 83 dealt with the horizontal control datum for the US, Mexico, Canada and Central America.
NAD 27 is based on the latitude and longitude, and the direction between two points, whereas, the NAD87 is an earth centered datum which has no initial point or direction.
Unlike the NAD 83, the NAD 27 is not capable of supporting the three-dimensional capabilities of modern positioning technology. Moreover, the North American Datum 27 and the North American Datum 83 are also different in their ellipsoids. It has been seen that the centre points of the NAD 27 and NAD 83 are in different locations.
Well, when talking about accuracy, it has been said that the North American Datum of 1983 is more accurate than the North American Datum of 1927. This is because the NAD 83 uses modern technology, whereas the NAD 27 was done manually.
Summary:
1. Although the NAD 27 and NAD 83 are both geodetic systems, each one of them is based on diffrent measurements.
2. The North American Datum 27 was based on Clarke Ellipsoid, which dealt with the manual surveying of the whole continent. The foundation of the North American Datum 83 was based on the Geodetic Reference System (GRS) of 1980.
3. Unlike the NAD 83, the NAD 27 is not capable of supporting the three-dimensional capabilities of modern positioning technology.
4. The NAD 27 and the NAD 83 are different in their ellipsoids.
5. When talking about accuracy, it has been said that the North American Datum of 1983 is more accurate than the North American Datum of 1927.
6. The NAD 83 uses modern technology; the NDA 27 has been done only manually.