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Hotine Oblique Mercator

Release 9.2
Last modified August 3, 2007
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Also known as Oblique Cylindrical Orthomorphic, this is an oblique rotation of the Mercator projection. Developed for conformal mapping of areas that are obliquely oriented and do not follow a north–south or east–west trend.
Learn more about the Mercator projection

Illustration of the Hotine Oblique Mercator projection

Projection method

Cylindrical. Oblique aspect of the Mercator projection. Oblique Mercator has several different types. You can define the tilt of the projection by either specifying two points or a point and an angle measuring east of north (the azimuth).

By default, the coordinate origin of the projected coordinates is located where the central line of the projection crosses the equator. As an example, if you use an Oblique Mercator (natural origin) for West Virginia, while the center of the projection is -80.75, 38.5, the natural origin is approximately -112.8253, 0.0. You can move the projection origin to the center of your data by using the Two-Point Center or Azimuth Center cases.

Line of tangency

A single oblique great-circle line or secancy along two oblique small circles parallel to and equidistant from the central great circle.

Linear graticules

Two meridians 180° apart.



Conformal. Local shapes are true.


Distortion increases with distance from the central line.


Local angles are correct.


True along the chosen central line.


Use should be limited to regions near the central line. When using a spheroid, constant scale along the central line and perfect conformality cannot be maintained simultaneously.

Uses and applications

Ideal for conformal mapping of regions that have an oblique orientation.

Used for large-scale mapping in the Alaskan panhandle. Switzerland uses a different implementation of Oblique Mercator by Rosenmund, while Madagascar uses the Laborde version. These implementations are not compatible with the Oblique Mercator projection that is available in ArcInfo workstation.



Azimuth case

Two Point case


Type 1 uses a central line defined by two points.

Type 2 uses a central line defined by one point and its angle of azimuth.

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