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. 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 38.5 N, 80.75 W, the natural origin is approximately 0.0 N, 112.8253 W. You can move the projection origin to the center of your data by using the two-point center or azimuth center cases. A single oblique great-circle line or secancy along two oblique small circles parallel to and equidistant from the central great circle. 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. 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. Source.