1MAPIT(3NCARG) NCAR GRAPHICS MAPIT(3NCARG)
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6 MAPIT - Draws lines on a map.
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9 CALL MAPIT (RLAT,RLON,IFST)
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12 #include <ncarg/ncargC.h>
13 void c_mapit (float rlat, float rlon, int ifst)
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17 RLAT and RLON
18 (input expressions, of type REAL) specify the latitude and
19 longitude of a point to which the "pen" is to be moved.
20 Both are given in degrees. RLAT must be between -90. and
21 +90., inclusive; RLON must be between -540. and +540.,
22 inclusive.
23 IFST (an input expression, of type INTEGER) is 0 to do a "pen-
25 up" move, 1 to do a "pen-down" move only if the distance
26 from the last point to the new point is greater than 'MV'
27 plotter units, and 2 or greater to do a "pen-down" move
28 regardless of the distance from the last point to the new
29 one.
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32 The C-binding argument descriptions are the same as the FORTRAN
33 argument descriptions.
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36 MAPIT is used to draw lines on the map; it is called by EZMAP itself
37 and, if desired, by the user. MAPIT attempts to omit nonvisible
38 portions of lines and to handle "crossover," a jump from one end of the
39 map to the other caused by the projection of the globe onto a flat
40 surface. Crossover can occur on cylindrical and conical projections;
41 MAPIT handles it gracefully on the former and not so well on the
42 latter.
43 To draw the projection of a line defined by a series of lat/lon
45 coordinates, start by calling MAPIT with the coordinates of the first
46 point and with IFST = 0. Then, call MAPIT repeatedly with the
47 coordinates of the next point along the line and with IFST = 1 or 2.
48 (IFST = 2 is normally used only for the final point, to ensure closure
49 with a line drawn by another series of calls.) Finally, if the next
50 thing your program does is stop, call FRAME, or change attributes like
51 color or line width, you should call MAPIQ to flush MAPIT's buffers.
52 The EZMAP parameter 'DL' determines whether MAPIT draws solid lines or
54 dotted lines. Dotted lines are drawn using calls to POINTS. Solid lines
55 are drawn using calls to DASHD, FRSTD, and VECTD. The parameters 'DD'
56 and 'MV' also affect MAPIT's behavior. See the descriptions of these
57 parameters in the ezmap_params man page.
58 Keep in mind the following:
60 · The projection of the line segment joining two points on the globe
62 is considered to be the straight-line segment joining the
63 projections of the points; no attempt is made to project it as if
64 it were a portion of a great circle.
65 · If both endpoints of a line segment are visible, the segment is
67 considered to be entirely visible.
68 · If both endpoints are invisible, the segment is considered to be
70 entirely invisible.
71 · If one endpoint is visible and the other is not, a new point is
73 interpolated at the boundary between the visible and invisible
74 portions. Only visible portions of the line are drawn.
75 Because of these considerations, points defining a line should not be
77 too far apart on the globe.
78 There are two types of boundaries between visible and invisible
80 regions:
81 · The limb is a boundary between a projectable region and an
83 unprojectable one. The limb may be circular, elliptical, or some
84 other shape, depending on the projection being used. For example,
85 an orthographic projection has as its limb a circle, centered at
86 (0,0), with a radius of 1.
87 · The perimeter is a rectangular or elliptical boundary defined by
89 EZMAP parameters set by you to specify the region you wish to view.
90
92 Use the ncargex command to see the following relevant examples: cmpgci,
93 cmptra, mpexfi.
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96 To use MAPIT or c_mapit, load the NCAR Graphics libraries ncarg,
97 ncarg_gks, and ncarg_c, preferably in that order.
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100 Online: ezmap, ezmap_params, mapaci, mapbla, mapblm, mapdrw, mapeod,
101 mapfst, mapgci, mapgrd, mapgrm, mapgtc, mapgti, mapgtl, mapgtr, mapint,
102 mapiq, mapiqa, mapiqd, mapiqm, mapita, mapitd, mapitm, maplbl, maplmb,
103 maplot, mappos, maproj, maprs, maprst, mapsav, mapset, mapstc, mapsti,
104 mapstl, mapstr, maptra, maptri, maptrn, mapusr, mapvec, mpchln, mpfnme,
105 mpgetc, mpgeti, mpgetl, mpgetr, mpglty, mpiaty, mpifnb, mpilnb, mpiola,
106 mpiosa, mpipai, mpipan, mpipar, mpisci, mplnam, mplndm, mplndr, mplnri,
107 mpname, mprset, mpsetc, mpseti, mpsetl, mpsetr, supmap, supcon,
108 ncarg_cbind
109 Hardcopy: NCAR Graphics Contouring and Mapping Tutorial
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113 Copyright (C) 1987-2009
114 University Corporation for Atmospheric Research
115 The use of this Software is governed by a License Agreement.
116UNIX March 1993 MAPIT(3NCARG)