Redfearn's Formula, Grid to Geographic

Given Easting, Northing and Zone for a Universal Transverse Mercator (UTM) projection, calculate Latitude, Longitude, Grid convergence and Point Scale Factor.

• The calculations are performed using the GRS80 ellipsoid which is used for Australia's new coordinate system (the Geocentric Datum of Australia - GDA) and is also compatible with the global coordinate system (WGS84) (a = 6,378,137.0 metres; 1/f = 298.25722210)
• Redfearn's formulae are used (Redfearn, Empire Survey Review, No. 69, 1948) to convert between Latitude & Longitude and easting, northing & zone for a UTM projection, such as the Map Grid of Australia (MGA). These formulae are accurate to better than 1 mm in any zone.

• NOTE: Given, Latitude and Longitude to calculate Easting, Northing, Zone for a UTM projection, Grid convergence and Point Scale Factor use the Geographic to Grid Version of Redfearn's Formula.

[back to top]