Convergence of the Meridian
P is a reference location in the projection-based SRF
The central meridian appears as a straightline (the Y-axis)
Meridians may or may not curve(one exception is the Mercator projection)
T is the tangent line to the meridian at P
? is the Convergence of the Meridian
The convergence of the meridian is theangle between SRF North and true Northon the ORS (positive clockwise)
The angle ? is the rotation angle needed torotate a vector in the Projection-based SRFto true North when siting a reference vectoronto a canonical LTP
The formula for computing the convergence of the meridianranges from very simple (0 for the Mercator projection-based SRFs) to very complex for Transverse Mercator