This projection is very similar to Lambert Conformal Conic, described previously. However, rather than specifying two standard parallels, one standard parallel and a scale factor are specified.
Conical projections with one standard parallel are normally considered to maintain the nominal map scale along the parallel of latitude which is the line of contact between the imagined cone and the ellipsoid. For a one standard parallel Lambert, the natural origin of the projected coordinate system is the intersection of the standard parallel with the longitude of origin (central meridian). To maintain the conformal property, the spacing of the parallels is variable and increases with increasing distance from the standard parallel, while the meridians are all straight lines radiating from a point on the prolongation of the ellipsoid’s minor axis.
Sometimes it is desirable to limit the maximum positive scale distortion by distributing it more evenly over the map area extent. This may be achieved by introducing a scale factor on the standard parallel of slightly less than unity, thus making it unity on two parallels either side of it. Some former French territories were mapped using this method. This is the same effect as choosing two specific standard parallels in the first place. The projection is then a Lambert Conformal Conic with two standard parallels.
For the one standard parallel Lambert, the latitude of natural origin is the standard parallel. The longitude of natural origin is the central meridian. Where the central meridian cuts the one standard parallel will be the natural origin of the projected coordinate system. Any number of Lambert projection zones may be formed according to which standard parallel or standard parallels are chosen, exemplified by the United States State Plane coordinate zones. They are normally chosen in the one standard parallel case to approximately bisect the latitudinal extent of the country or area.
Meridians are straight lines converging at a pole.
Parallels are arcs of concentric circles concave toward a pole and centered at a pole.
Meridian spacing is true on the standard parallels and decreases toward the pole. Parallel spacing increases away from the standard parallels and decreases between them. Meridians and parallels intersect each other at right angles. The graticule spacing retains the property of conformality. The graticule is symmetrical.
Linear scale is true on standard parallels.
Large countries in the mid-latitudes having an east-west orientation.
Petrotechnical Open Software Corporation: Epicentre v2.2 Usage Guide. See www.posc.org/Epicentre.2_2.
This projection contains these unique parameters:
Latitude of natural origin Control line of the projection, that is, the standard parallel
Longitude of natural origin Longitude of the natural origin, that is, the central meridian
Scale factor at natural origin Scale factor at the natural origin on the standard parallel