MAP(7) MAP(7)
NAME
map, mapdemo - draw maps on various projections
SYNOPSIS
map projection [ option ... ]
mapdemo
DESCRIPTION
Map prepares on the standard output a map suitable for dis-
play by any plotting filter described in plot(1). A menu of
projections is produced in response to an unknown
projection. Mapdemo is a short course in mapping.
The default data for map are world shorelines. Option -f
accesses more detailed data classified by feature.
-f [ feature ... ]
Features are ranked 1 (default) to 4 from major to
minor. Higher-numbered ranks include all lower-
numbered ones. Features are
shore[1-4] seacoasts, lakes, and islands; option -f
always shows shore1
ilake[1-2] intermittent lakes
river[1-4] rivers
iriver[1-3] intermittent rivers
canal[1-3] 3=irrigation canals
glacier
iceshelf[12]
reef
saltpan[12]
country[1-3] 2=disputed boundaries, 3=indefinite
boundaries
state states and provinces (US and Canada only)
In other options coordinates are in degrees, with north lat-
itude and west longitude counted as positive.
-l S N E W
Set the southern and northern latitude and the eastern
and western longitude limits. Missing arguments are
filled out from the list -90, 90, -180, 180, or lesser
limits suitable to the projection at hand.
-k S N E W
Set the scale as if for a map with limits -l S N E W .
Do not consider any -l or -w option in setting scale.
-o lat lon rot
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MAP(7) MAP(7)
Orient the map in a nonstandard position. Imagine a
transparent gridded sphere around the globe. Turn the
overlay about the North Pole so that the Prime Meridian
(longitude 0) of the overlay coincides with meridian
lon on the globe. Then tilt the North Pole of the
overlay along its Prime Meridian to latitude lat on the
globe. Finally again turn the overlay about its `North
Pole' so that its Prime Meridian coincides with the
previous position of meridian rot. Project the map in
the standard form appropriate to the overlay, but pre-
senting information from the underlying globe. Missing
arguments are filled out from the list 90, 0, 0. In
the absence of -o, the orientation is 90, 0, m, where m
is the middle of the longitude range.
-w S N E W
Window the map by the specified latitudes and longi-
tudes in the tilted, rotated coordinate system. Miss-
ing arguments are filled out from the list -90, 90,
-180, 180. (It is wise to give an encompassing -l
option with -w. Otherwise for small windows computing
time varies inversely with area!)
-d n For speed, plot only every nth point.
-r Reverse left and right (good for star charts and
inside-out views).
-v Verso. Switch to a normally suppressed sheet of the
map, such as the back side of the earth in orthographic
projection.
-s1
-s2 Superpose; outputs for a -s1 map (no closing) and a -s2
map (no opening) may be concatenated.
-g dlat dlon res
Grid spacings are dlat, dlon. Zero spacing means no
grid. Missing dlat is taken to be zero. Missing dlon
is taken the same as dlat. Grid lines are drawn to a
resolution of res (2° or less by default). In the
absence of -g, grid spacing is 10°.
-p lat lon extent
Position the point lat, lon at the center of the plot-
ting area. Scale the map so that the height (and
width) of the nominal plotting area is extent times the
size of one degree of latitude at the center. By
default maps are scaled and positioned to fit within
the plotting area. An extent overrides option -k.
-c x y rot
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MAP(7) MAP(7)
After all other positioning and scaling operations have
been performed, rotate the image rot degrees counter-
clockwise about the center and move the center to posi-
tion x, y, where the nominal plotting area is -1≤x≤1,
-1≤y≤1. Missing arguments are taken to be 0. -x Allow
the map to extend outside the nominal plotting area.
-m [ file ... ]
Use map data from named files. If no files are named,
omit map data. Names that do not exist as pathnames
are looked up in a standard directory, which contains,
in addition to the data for -f,
world World Data Bank I (default)
states US map from Census Bureau
counties US map from Census Bureau
The environment variables MAP and MAPDIR change the
default map and default directory.
-b [lat0 lon0 lat1 lon1... ]
Suppress the drawing of the normal boundary (defined by
options -l and -w). Coordinates, if present, define
the vertices of a polygon to which the map is clipped.
If only two vertices are given, they are taken to be
the diagonal of a rectangle. To draw the polygon, give
its vertices as a -u track.
-t file ...
The files contain lists of points, given as latitude-
longitude pairs in degrees. If the first file is named
`-', the standard input is taken instead. The points
of each list are plotted as connected `tracks'.
Points in a track file may be followed by label
strings. A label breaks the track. A label may be
prefixed by ", `:', or `!' and is terminated by a new-
line. An unprefixed string or a string prefixed with "
is displayed at the designated point. The first word
of a `:' or `!' string names a special symbol (see
option -y). An optional numerical second word is a
scale factor for the size of the symbol, 1 by default.
A `:' symbol is aligned with its top to the north; a
`!' symbol is aligned vertically on the page.
-u file ...
Same as -t, except the tracks are unbroken lines. (-t
tracks appear as dot-dashed lines if the plotting fil-
ter supports them.)
-y file
The file contains plot(6)-style data for `:' or `!'
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MAP(7) MAP(7)
labels in -t or -u files. Each symbol is defined by a
comment :name then a sequence of `m' and `v' commands.
Coordinates (0,0) fall on the plotting point. Default
scaling is as if the nominal plotting range were `ra -1
-1 1 1'; `ra' commands in file change the scaling.
Projections
Equatorial projections centered on the Prime Meridian (lon-
gitude 0). Parallels are straight horizontal lines.
mercator equally spaced straight meridians, conformal,
straight compass courses
sinusoidal equally spaced parallels, equal-area, same as
`bonne 0'.
cylequalarea lat0
equally spaced straight meridians, equal-
area, true scale on lat0
cylindrical central projection on tangent cylinder
rectangular lat0
equally spaced parallels, equally spaced
straight meridians, true scale on lat0
gall lat0 parallels spaced stereographically on prime
meridian, equally spaced straight meridians,
true scale on lat0
mollweide (homalographic) equal-area, hemisphere is a
circle
gilbert() sphere conformally mapped on hemi-
sphere and viewed orthographically
gilbert globe mapped conformally on hemisphere,
viewed orthographically
Azimuthal projections centered on the North Pole. Parallels
are concentric circles. Meridians are equally spaced radial
lines.
azequidistant equally spaced parallels, true distances from
pole
azequalarea equal-area
gnomonic central projection on tangent plane, straight
great circles
perspective dist
viewed along earth's axis dist earth radii
from center of earth
orthographic viewed from infinity
stereographic conformal, projected from opposite pole
laue radius = tan(2xcolatitude), used in X-ray
crystallography
fisheye n stereographic seen from just inside medium
with refractive index n
newyorker r radius = log(colatitude/r): New Yorker map
from viewing pedestal of radius r degrees
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MAP(7) MAP(7)
Polar conic projections symmetric about the Prime Meridian.
Parallels are segments of concentric circles. Except in the
Bonne projection, meridians are equally spaced radial lines
orthogonal to the parallels.
conic lat0 central projection on cone tangent at lat0
simpleconic lat0 lat1
equally spaced parallels, true scale on lat0
and lat1
lambert lat0 lat1
conformal, true scale on lat0 and lat1
albers lat0 lat1
equal-area, true scale on lat0 and lat1
bonne lat0 equally spaced parallels, equal-area, paral-
lel lat0 developed from tangent cone
Projections with bilateral symmetry about the Prime Meridian
and the equator.
polyconic parallels developed from tangent cones,
equally spaced along Prime Meridian
aitoff equal-area projection of globe onto 2-to-1
ellipse, based on azequalarea
lagrange conformal, maps whole sphere into a circle
bicentric lon0 points plotted at true azimuth from two cen-
ters on the equator at longitudes ±lon0,
great circles are straight lines (a stretched
gnomonic )
elliptic lon0 points plotted at true distance from two cen-
ters on the equator at longitudes ±lon0
globular hemisphere is circle, circular arc meridians
equally spaced on equator, circular arc par-
allels equally spaced on 0- and 90-degree
meridians
vandergrinten sphere is circle, meridians as in globular,
circular arc parallels resemble mercator
Doubly periodic conformal projections.
guyou W and E hemispheres are square
square world is square with Poles at diagonally
opposite corners
tetra map on tetrahedron with edge tangent to Prime
Meridian at S Pole, unfolded into equilateral
triangle
hex world is hexagon centered on N Pole, N and S
hemispheres are equilateral triangles
Miscellaneous projections.
harrison dist angle
oblique perspective from above the North
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MAP(7) MAP(7)
Pole, dist earth radii from center of earth,
looking along the Date Line angle degrees off
vertical
trapezoidal lat0 lat1
equally spaced parallels, straight meridians
equally spaced along parallels, true scale at
lat0 and lat1 on Prime Meridian
lune(lat,angle) conformal, polar cap above
latitude lat maps to convex lune with given
angle at 90oE and 90oW
Retroazimuthal projections. At every point the angle
between vertical and a straight line to `Mecca', latitude
lat0 on the prime meridian, is the true bearing of Mecca.
mecca lat0 equally spaced vertical meridians
homing lat0 distances to Mecca are true
Maps based on the spheroid. Of geodetic quality, these pro-
jections do not make sense for tilted orientations. For
descriptions, see corresponding maps above.
sp_mercator
sp_albers lat0 lat1
EXAMPLES
map perspective 1.025 -o 40.75 74
A view looking down on New York from 100 miles (0.025
of the 4000-mile earth radius) up. The job can be done
faster by limiting the map so as not to `plot' the
invisible part of the world: `map perspective 1.025 -o
40.75 74 -l 20 60 30 100'. A circular border can be
forced by adding option `-w 77.33'. (Latitude 77.33°
falls just inside a polar cap of opening angle arc-
cos(1/1.025) = 12.6804°.)
map mercator -o 49.25 -106 180
An `equatorial' map of the earth centered on New York.
The pole of the map is placed 90o away (40.75+49.25=90)
on the other side of the earth. A 180° twist around
the pole of the map arranges that the `Prime Meridian'
of the map runs from the pole of the map over the North
Pole to New York instead of down the back side of the
earth. The same effect can be had from map mercator -o
130.75 74
map albers 28 45 -l 20 50 60 130 -m states
A customary curved-latitude map of the United States.
map harrison 2 30 -l -90 90 120 240 -o 90 0 0
A fan view covering 60° on either side of the Date
Line, as seen from one earth radius above the North
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MAP(7) MAP(7)
Pole gazing at the earth's limb, which is 30° off ver-
tical. The -o option overrides the default -o 90 0
180, which would rotate the scene to behind the
observer.
FILES
/lib/map/[1-4]?? World Data Bank II, for -f
/lib/map/* maps for -m
/lib/map/*.x map indexes
/bin/aux/mapd Map driver program
SOURCE
/sys/src/cmd/map
SEE ALSO
map(6), plot(1)
DIAGNOSTICS
`Map seems to be empty'-a coarse survey found zero extent
within the -l and -w bounds; for maps of limited extent the
grid resolution, res, or the limits may have to be refined.
BUGS
Windows (option -w) cannot cross the Date Line. No borders
appear along edges arising from visibility limits. Segments
that cross a border are dropped, not clipped. Excessively
large scale or -d setting may cause long line segments to be
dropped. Map tries to draw grid lines dotted and -t tracks
dot-dashed. As very few plotting filters properly support
curved textured lines, these lines are likely to appear
solid. The west-longitude-positive convention betrays Yan-
kee chauvinism. Gilbert should be a map from sphere to
sphere, independent of the mapping from sphere to plane.
Page 7 Plan 9 (printed 12/22/24)