This conic projection was designed by Lambert (1772) and has been
used extensively for mapping of regions with predominantly east-west
orientation, just like the Albers projection. Unlike the Albers
projection, Lambert's conformal projection is not equal-area.
The parallels are arcs of circles with a common origin, and
meridians are the equally spaced radii of these circles. As with
Albers projection, it is only the two standard parallels that are
distortion-free. To select this projection in **GMT** you must
provide the same information as for the Albers projection, i.e.

- Longitude and latitude of the projection center
- Two standard parallels
- Map scale in inch/degree or 1:xxxxx notation
(
**-Jl**), or map width (**-JL**)

The Lambert conformal projection has been used for basemaps for all the 48 contiguous States with the two fixed standard parallels 33N and 45N. We will generate a map of the continental USA using these parameters. Note that with all the projections you have the option of selecting a rectangular border rather than one defined by meridians and parallels. Here, we choose the regular WESN region, a ``fancy'' basemap frame, and use degrees west for longitudes. The generating commands used were

gmtset BASEMAP_TYPE FANCY PLOT_DEGREE_FORMAT ddd:mm:ssF GRID_CROSS_SIZE_PRIMARY 0.05i pscoast -R-130/-70/24/52 -Jl-100/35/33/45/1:50000000 -B10g5 -Dl -N1/1p -N2/0.5p -A500 -Glightgray \ -W0.25p -P > GMT_lambert_conic.ps gmtset GRID_CROSS_SIZE_PRIMARY 0

The choice for projection center does not affect the projection but it indicates which meridian (here 100W) will be vertical on the map. The standard parallels were originally selected by Adams to provide a maximum scale error between latitudes 30.5N and 47.5N of 0.5-1%. Some areas, like Florida, experience scale errors of up to 2.5%.