Hotine Oblique Mercator 2-Point Projection

Aleutian Islands, Alaska

Hotine Oblique Mercator Projection

Scale = 1

False Easting = 0 False Northing = 0

Central Scale Factor = 1 Central Latitude = 0

Standard Parallel = 56 2nd Standard Parallel = 58

1st Meridian = -133 2nd Meridian = -135

Rotate U/V to X/Y = True

Offset by U = True


Projection Characteristics

The Hotine Oblique Mercator 2-Point projection is a cylindrical, conformal projection. The scale is accurate along the chosen central line by the longitude/latitude settings below. This projection is useful for oblique areas (areas that do not follow lines of latitude and longitude), such as the Alaska panhandle because the central line does not have to follow a line of constant longitude. This projection is typically used with areas that are state or province sized and it is not suitable for maps of the world. There are two forms of the Hotine projection equation. The Hotine Oblique Mercator 2-Point projection is defined by selecting two points to form a line (Alternate A, Snyder).


Projection Parameters




Specifies the units used in the map.


Specifies the unit scale of the projected map, relative to meters. For example, a scale of one means one unit in the projected map equals one meter; a scale of two means two units in the projected map equal one meter; etc.

False Easting

Specifies the false easting, or horizontal offset, of the projected coordinates, in meters. False Eastings and False Northings are added to the underlying "projected" coordinates as a way to arbitrarily offset their internal XY coordinates after the projection. Unless you have a reason for using these offset values, do not use them. These values do not affect the latitude/longitude coordinates for the map, only the internal coordinates used to plot the map on the screen. If you use False Easting and False Northing offsets for a map, any subsequent boundaries you append to the map must also use these same offsets if you want the imported boundaries to be drawn in the correct relative position to the existing boundaries.

False Northing

Specifies the false northing, or vertical offset, of the projected coordinates, in meters. See above.

Central Scale Factor (KO)

Specifies the central scaling factor for the projection. This value is often set to 1.0, but may be set to another value for specific applications.

Central Latitude

Specifies the central latitude of the projection in degrees. The Central Latitude value typically should be defined as the latitudinal center of the map you are going to produce, and should typically be defined as the center of the map.

Standard Parallel

Defines one end of the Y extent for the central line.

1st Meridian

Defines one end of the X extent for the central line.

2nd Standard Parallel

Defines the other end of the Y extent for the central line.

2nd Meridian

Defines the other end of the X extent for the central line.

Rotate U/V to X/Y

u,v are unrectified coordinates that follow the central line of the projection.  x,y are rectified rectangular coordinates.  When True, u,v are rotated to x,y. See Snyder page 70.

Offset by U

When True, u coordinates are offset to remove the Us center component, to normalize the origin of the u axis.  This is typically required for State Plane coordinate systems that use the Hotine Oblique Mercator projection method.



See Also

Introduction to Map Projections

Geometric Forms of Projection

Characteristics of Projections



Convert Projection

Latitude/Longitude Coordinates

Latitude/Longitude in Decimal Degrees

Using Scaling to Minimize Distortion in Latitude/Longitude Projects

Projection References