ncl_mapit - Man Page

Draws lines on a map.



C-Binding Synopsis

#include <ncarg/ncargC.h>

void c_mapit (float rlat, float rlon, int ifst)



(input expressions, of type REAL) specify the latitude and longitude of a point to which the "pen" is to be moved. Both are given in degrees. RLAT must be between -90. and +90., inclusive; RLON must be between -540. and +540., inclusive.


(an input expression, of type INTEGER) is 0 to do a "pen-up" move, 1 to do a "pen-down" move only if the distance from the last point to the new point is greater than 'MV' plotter units, and 2 or greater to do a "pen-down" move regardless of the distance from the last point to the new one.

C-Binding Description

The C-binding argument descriptions are the same as the FORTRAN  argument descriptions.


MAPIT is used to draw lines on the map; it is called by EZMAP itself and, if desired, by the user. MAPIT attempts to omit nonvisible portions of lines and to handle "crossover," a jump from one end of the map to the other caused by the projection of the globe onto a flat surface. Crossover can  occur on cylindrical and conical projections; MAPIT handles  it gracefully on the former and not so well on the latter.

To draw the projection of a line defined by a series of lat/lon coordinates, start by calling MAPIT with the coordinates of the first point and with IFST = 0.  Then, call MAPIT repeatedly with the coordinates of the next point along the line and with IFST = 1 or 2. (IFST = 2 is normally used only for the final point, to ensure closure with a line drawn by another series of calls.) Finally, if the next thing your program does is stop, call FRAME, or change attributes like color or line width, you should call MAPIQ to flush MAPIT's buffers.

The EZMAP parameter 'DL' determines whether MAPIT draws solid lines or dotted lines. Dotted lines are drawn using calls to POINTS. Solid lines are drawn using calls to DASHD, FRSTD, and VECTD. The parameters 'DD' and 'MV' also affect MAPIT's behavior. See the descriptions of these parameters in the ezmap_params man page.

Keep in mind the following:

Because of these considerations, points defining a line should not be too far apart on the globe.

There are two types of boundaries between visible and invisible regions:


Use the ncargex command to see the following relevant examples:  cmpgci, cmptra, mpexfi.


To use MAPIT or c_mapit, load the NCAR Graphics libraries ncarg, ncarg_gks, and ncarg_c, preferably in that order.  

See Also

Online: ezmap, ezmap_params, mapaci, mapbla, mapblm, mapdrw, mapeod, mapfst, mapgci, mapgrd, mapgrm, mapgtc, mapgti, mapgtl, mapgtr, mapint, mapiq, mapiqa, mapiqd, mapiqm, mapita, mapitd, mapitm, maplbl, maplmb, maplot, mappos, maproj, maprs, maprst, mapsav, mapset, mapstc, mapsti, mapstl, mapstr, maptra, maptri, maptrn, mapusr, mapvec, mpchln, mpfnme, mpgetc, mpgeti, mpgetl, mpgetr, mpglty, mpiaty, mpifnb, mpilnb, mpiola, mpiosa, mpipai, mpipan, mpipar, mpisci, mplnam, mplndm, mplndr, mplnri, mpname, mprset, mpsetc, mpseti, mpsetl, mpsetr, supmap, supcon, ncarg_cbind

Hardcopy:  NCAR Graphics Contouring and Mapping Tutorial