Merge branch 'master' into debug-grdcut

Author: seisman

examples/projections/azim/azim_lambert.py

@@ -2,6 +2,11 @@
 Lambert Azimuthal Equal Area
 ============================
 
+This projection was developed by Johann Heinrich Lambert in 1772 and is typically used
+for mapping large regions like continents and hemispheres. It is an azimuthal,
+equal-area projection, but is not perspective. Distortion is zero at the center of the
+projection, and increases radially away from this point.
+
 ``Alon0/lat0[/horizon]/width``: ``lon0`` and ``lat0`` specifies the projection center.
 ``horizon`` specifies the max distance from projection center (in degrees, <= 180,
 default 90).

examples/projections/conic/conic_albers.py

@@ -2,6 +2,15 @@
 Albers Conic Equal Area
 =======================
 
+This projection, developed by Heinrich C. Albers in 1805, is predominantly used to map
+regions of large east-west extent, in particular the United States. It is a conic,
+equal-area projection, in which parallels are unequally spaced arcs of concentric
+circles, more closely spaced at the north and south edges of the map. Meridians, on the
+other hand, are equally spaced radii about a common center, and cut the parallels at
+right angles. Distortion in scale and shape vanishes along the two standard parallels.
+Between them, the scale along parallels is too small; beyond them it is too large.
+The opposite is true for the scale along meridians.
+
 ``Blon0/lat0/lat1/lat2/width``: Give projection center ``lon0/lat0`` and two standard
 parallels ``lat1/lat2``.
 """

examples/projections/conic/conic_equidistant.py

@@ -2,6 +2,11 @@
 Equidistant conic
 =================
 
+The equidistant conic projection was described by the Greek philosopher Claudius
+Ptolemy about A.D. 150. It is neither conformal or equal-area, but serves as a
+compromise between them. The scale is true along all meridians and the
+standard parallels.
+
 ``Dlon0/lat0/lat1/lat2/width``: Give projection center ``lon0/lat0``, two standard
 parallels ``lat1/lat2``, and the map width.
 """

examples/projections/conic/conic_lambert.py

@@ -2,6 +2,13 @@
 Lambert Conic Conformal Projection
 ==================================
 
+This conic projection was designed by the Alsatian mathematician Johann Heinrich
+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.
+
 ``Llon0/lat0/lat1/lat2/width``: Give projection center ``lon0/lat0``, two standard
 parallels ``lat1/lat2``, and the map width.
 """

examples/projections/conic/polyconic.py

@@ -2,6 +2,22 @@
 Polyconic Projection
 ====================
 
+The polyconic projection, in Europe usually referred to as the American polyconic
+projection, was introduced shortly before 1820 by the Swiss-American cartographer
+Ferdinand Rodulph Hassler (1770–1843). As head of the Survey of the Coast, he was
+looking for a projection that would give the least distortion for mapping the coast of
+the United States. The projection acquired its name from the construction of each
+parallel, which is achieved by projecting the parallel onto the cone while it is rolled
+around the globe, along the central meridian, tangent to that parallel. As a
+consequence, the projection involves many cones rather than a single one used in
+regular conic projections.
+
+The polyconic projection is neither equal-area, nor conformal. It is true to scale
+without distortion along the central meridian. Each parallel is true to scale as well,
+but the meridians are not as they get further away from the central meridian. As a
+consequence, no parallel is standard because conformity is lost with the lengthening of
+the meridians.
+
 ``Poly/width``:  The only additional argument for the projection is the map width.
 """
 import pygmt

examples/projections/cyl/cyl_cassini.py

@@ -2,6 +2,15 @@
 Cassini Cylindrical
 ============================
 
+This cylindrical projection was developed in 1745 by César-François Cassini de Thury
+for the survey of France. It is occasionally called Cassini-Soldner since the latter
+provided the more accurate mathematical analysis that led to the development of the
+ellipsoidal formulae. The projection is neither conformal nor equal-area, and behaves
+as a compromise between the two end-members. The distortion is zero along the central
+meridian. It is best suited for mapping regions of north-south extent. The central
+meridian, each meridian 90° away, and equator are straight lines; all other meridians
+and parallels are complex curves.
+
 ``Clon0/lat0/width``: ``lon0`` and ``lat0`` specifies the projection center.
 """
 import pygmt

examples/projections/cyl/cyl_equal_area.py

@@ -2,7 +2,12 @@
 Cylindrical equal-area
 ======================
 
-``Ylon0/lat0/width``: Give central meridian ``lon0``, the standard parallel ``lat0``, and the figure ``width``.
+This cylindrical projection is actually several projections, depending on what
+latitude is selected as the standard parallel. However, they are all equal area and
+hence non-conformal. All meridians and parallels are straight lines.
+
+``Ylon0/lat0/width``: Give central meridian ``lon0``, the standard parallel ``lat0``,
+and the figure ``width``.
 """
 import pygmt
 

examples/projections/cyl/cyl_equidistant.py

@@ -2,6 +2,10 @@
 Cylindrical equidistant
 =======================
 
+This simple cylindrical projection is really a linear scaling of longitudes and
+latitudes. The most common form is the Plate Carrée projection, where the scaling of
+longitudes and latitudes is the same. All meridians and parallels are straight lines.
+
 ``Qwidth``: Give the figure ``width``.
 """
 import pygmt

examples/projections/cyl/cyl_mercator.py

@@ -2,6 +2,16 @@
 Mercator
 ========
 
+The Mercator projection takes its name from the Flemish cartographer Gheert Cremer,
+better known as Gerardus Mercator, who presented it in 1569. The projection is a
+cylindrical and conformal, with no distortion along the equator. A major navigational
+feature of the projection is that a line of constant azimuth is straight. Such a line
+is called a rhumb line or loxodrome. Thus, to sail from one point to another one only
+had to connect the points with a straight line, determine the azimuth of the line, and
+keep this constant course for the entire voyage. The Mercator projection has been used
+extensively for world maps in which the distortion towards the polar regions grows
+rather large.
+
 ``M[lon0/][lat0/]width``: Give central meridian ``lon0`` (optional) and
 standard parallel ``lat0`` (optional).
 """

examples/projections/cyl/cyl_miller.py

@@ -2,6 +2,13 @@
 Miller cylindrical
 ==================
 
+This cylindrical projection, presented by Osborn Maitland Miller of the American
+Geographic Society in 1942, is neither equal nor conformal. All meridians and
+parallels are straight lines. The projection was designed to be a compromise between
+Mercator and other cylindrical projections. Specifically, Miller spaced the parallels
+by using Mercator’s formula with 0.8 times the actual latitude, thus avoiding the
+singular poles; the result was then divided by 0.8.
+
 ``J[lon0/]width``: Give the optional central meridian ``lon0`` and the figure ``width``.
 """
 import pygmt