Understanding Map Projections

HOTINE OBLIQUE MERCATOR
LINEAR GRATICULES
Two meridians 180 degrees apart.
PROPERTIES
Shape
Conformal. Local shapes are true.
Area
Distortion increases with distance from the central
line.
Direction
Local angles are correct.
The State Plane Coordinate System uses Hotine Azimuth Natural
Origin for the Alaskan panhandle.
DESCRIPTION
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.
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).
Distance
True along the chosen central line.
LIMITATIONS
Use should be limited to regions near the central
line. When using an ellipsoid, 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 aren’t compatible.
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.
Supported map projections• 63