A coordinate within the Mercator (M) 2D Spatial Reference Frame (SRF).
The Mercator projection-based Spatial Reference Frame is a cylindrical, conformal projection normally placed tangent to the equator of the Object Reference Model/Earth Reference Model (ORM/ERM). When secant, two rather than a single parallel are defined; alternatively this can be expressed as a "central scale factor" at the equator. By convention, only the scale factor along the equator is used. The equator is defined by the ORM/ERM.
The meridians of the Mercator 2D SRF are parallel, equally spaced lines, cut at right angles by straight parallels which are increasingly spaced toward each pole. The spacing of parallels at a given latitude on a spherical ORM is proportional to the secant of the latitude.
The major navigational feature of the Mercator projection is found in the fact that a sailing route between two points (on a spherical ORM) is realized as a straight line, if the direction or azimuth of the ship remains constant with respect to north (known as a loxodrome or rhumb line).
When used to define a 2D spatial reference frame, the resulting X and Y axes are measured in meters (rather than arc degrees), and a local origin offset is provided. The X axis lies along the equator, increasing in the easterly direction; the Y axis lies along a meridian (and therefore perpendicular to the equatorial parallel), increasing in a northerly direction, and forms a 2D right-handed coordinate system. The origin is defined by the intersection of the parametric meridian and the equator.
See the SEDRIS Spatial Reference Model (SRM) for additional details.
| SE_FLOAT64 | x; | (notes) |
|---|---|---|
| SE_FLOAT64 | y; | (notes) |
the center point for the LOD test
in meters; positive Eastward
in meters; positive Northward