MAP(7)MAP(7)NAME
map, mapdemo - draw maps on various projections
SYNOPSISmap projection [ option ... ]
mapdemo
DESCRIPTION
Map prepares on the standard output a map suitable for display by any
plotting filter described in plot(1). A menu of projections is pro‐
duced 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 latitude and
west longitude counted as positive.
-l S N E W
Set the southern and northern latitude and the eastern and western lon‐
gitude 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
Orient the map in a nonstandard position. Imagine a transparent grid‐
ded 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 presenting infor‐
mation 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 longitudes in the tilted,
rotated coordinate system. Missing 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 -s1map (no closing) and a -s2map (no open‐
ing) 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 plotting 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
After all other positioning and scaling operations have been performed,
rotate the image rot degrees counterclockwise about the center and move
the center to position 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 direc‐
tory, 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 newline. An unprefixed string or a string prefixed with " is dis‐
played 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 filter supports them.)
-y file
The file contains plot(6)-style data for or labels in -t or -u files.
Each symbol is defined by a comment :name then a sequence of and com‐
mands. Coordinates (0,0) fall on the plotting point. Default scaling
is as if the nominal plotting range were commands in file change the
scaling.
Projections
Equatorial projections centered on the Prime Meridian (longitude 0).
Parallels are straight horizontal lines.
mercator equally spaced straight meridians, conformal, straight
compass courses
sinusoidal equally spaced parallels, equal-area, same as
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 merid‐
ians, 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 hemisphere and
viewed orthographically
gilbert globe mapped conformally on hemisphere, viewed ortho‐
graphically
Azimuthal projections centered on the North Pole. Parallels are con‐
centric 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 cir‐
cles
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(2×colatitude), used in X-ray crystallogra‐
phy
fisheye n stereographic seen from just inside medium with refrac‐
tive index n
newyorker r radius = log(colatitude/r): New Yorker map from viewing
pedestal of radius r degrees
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, parallel 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 centers on the
equator at longitudes ±lon0, great circles are straight
lines (a stretched gnomonic )
elliptic lon0 points plotted at true distance from two centers on the
equator at longitudes ±lon0
globular hemisphere is circle, circular arc meridians equally
spaced on equator, circular arc parallels 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 cor‐
ners
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 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 90°E and 90°W
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 projections do
not make sense for tilted orientations. For descriptions, see corre‐
sponding maps above.
sp_mercator
sp_albers lat0 lat1
EXAMPLESmap 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 lim‐
iting the map so as not to `plot' the invisible part of the
world: A circular border can be forced by adding option (Lati‐
tude 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 90° 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 Pole gazing at the earth's
limb, which is 30° off vertical. 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 ALSOmap(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 bor‐
der 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 Yankee
chauvinism. Gilbert should be a map from sphere to sphere, independent
of the mapping from sphere to plane.
MAP(7)
