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MAP(7)                 Miscellaneous Information Manual                 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 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).

       -s
       Save the screen, don't erase before drawing.  Output made under -s must
       be appended to output of another map command.

       -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  -1x1,
       -1y1.  Missing arguments are taken to be 0.

       -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

       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(2xcolatitude), used in X-ray  crystallogra-
                      phy
       fisheye 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
       gilbert        sphere  mapped  conformally  to  hemisphere  and  viewed
                      orthographically, horizontal parallels

       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

       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
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 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(1.025) = 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 ALSO
       map(6), plot(1), road(7)
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.



                                                                        MAP(7)