term% cat index.txt MAP(5) File Formats Manual MAP(5)
NAME
map - digitized map formats
DESCRIPTION
Files used by map(7) are a sequence of structures of the form:
struct {
char patchlatitude;
char patchlongitude;
short n;
union {
struct {
short latitude;
short longitude;
} point[n];
struct {
short latitutde;
short longitude;
struct {
char latdiff;
char londiff;
} point[-n];
} highres;
} segment;
};
Patchlatitude and patchlongitude 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 coordi‐
nates of the southeast corner of the patch in units of 10 degrees.
Each segment of abs(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
succeeeding 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 patchlatitude then patch‐
longitude. A printable index to the first segment of each patch in a
file named map is kept in an associated file named map.x. Each line of
an index file contains patchlatitude, patchlongitude and the byte posi‐
tion of the patch in the map file.
SEE ALSO
map(7), map(3)
MAP(5)