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MAP(6)                           Games Manual                           MAP(6)

       map - digitized map formats

       Files used by map(7) are a sequence of structures of the form:

       struct {
            signed char patchlatitude;
            signed char patchlongitude;
            short n;
            union {
                 struct {
                      short latitude;
                      short longitude;
                 } point[n];
                 struct {
                      short latitude;
                      short longitude;
                      struct {
                           signed char latdiff;
                           signed char londiff;
                      } point[-n];
                 } highres;
            } segment;
       where  short  stands for 16-bit integers and there is no padding within
       or between structs.  Shorts are stored in little-endian order, low byte
       first.  To assure portability, map accesses them bytewise.

       Fields  and  tell  to  what 10-degree by 10-degree patch of the earth's
       surface a segment belongs.  Their values range from -9 to  8  and  from
       -18  to 17, respectively, and indicate the coordinates of the southeast
       corner of the patch in units of 10 degrees.

       Each segment of |n| points is connected; consecutive segments  are  not
       necessarily  related.   Latitude and longitude are measured in units of
       0.0001 radian.  If n is negative, then differences  to  the  first  and
       succeeding points are measured in units of 0.00001 radian.  Latitude is
       counted positive to the north and longitude positive to the west.

       The patches are ordered lexicographically by then A printable index  to
       the  first  segment  of  each  patch in a file named data is kept in an
       associated file named data.x.  Each line of an index file contains  and
       the  byte position of the patch in the map file.  Both the map file and
       the index file are ordered by patch latitude and longitude.

       The data comes from the World Data Bank I and II  and  U.S.  Government
       sources: the Census Bureau, Geological Survey, and CIA.