How Much Azimuth Distortion?

• Consider any conformal map projection

• P is a given location in the projected system

• The central meridian appears as a straightline (the Y-axis)

• Generally other meridians are curved(an 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 the anglebetween SRF North and “true” North onthe source ORM (positive clockwise)

Convergence of the Meridian

The formula for computing the convergence of the meridianranges from very simple (0 for the Mercator-based SRFs)to very complex for Transverse Mercator

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