Transverse Mercator Projection – Ibex Aviation Academy

Transverse Mercator

Transverse Mercator is useful for mapping countries or air-routes with large north-south extent
Unlike Normal Mercator, a meridian is selected as the parallel of tangency
Scale of Transverse Mercator is correct in a vertical band of 480 NM either side of the datum meridian
Scale expansion in all directions is proportional to secant of angular distance from datum meridian
Transverse Mercator is orthomorphic projection, since it meets the two requirements for orthomorphism
Scale expansion same in all directions around a point and meridians and parallels cut at right angles

In a Transverse Mercator, Parallel of latitudes are seen as an ellipses and meridians appear as complex curves
Latitudes appear circular near poles except equator which is seen as two parallel straight lines
Meridians are complex curves which emerge radially from poles
Datum meridian and its perpendicular meridian are straight lines
However, meridians and parallels cut at right angles making the chart orthomorphic

Scale expansion is more than 1% at larger distances from datum meridian
Shapes are distorted and areas appear larger than actual size due to scale expansion as we move away from the datum meridian
In order to use Transverse Mercator, datum meridians have to be selected depending on the area of map
Chart convergence changes constantly throughout the projection
At poles and equator, chart convergence is same at earth convergence but are incorrect elsewhere
Great Circles and Rhumb lines appear as complex curves
Equator, Datum Meridian and the Meridian perpendicular are seen as straight lines