V8/usr/man/man5/map.5

.TH MAP 5
.SH NAME
map \- digitized map formats
.SH DESCRIPTION
Files used by
.IR  map (7)
are a sequence of structures of the form:
.IP
.nf
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;
};
.fi
.PP
.I Patchlatitude
and
.I 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 coordinates of the
southeast corner of the patch in units of 10 degrees.
.PP
Each segment of
.I abs(n)
points is connected; consecutive segments
are not necessarily related.
.I Latitude
and
.I longitude
are measured in units of 0.0001 radian.
If 
.I n
is negative, then 
differences to the first and succeeeding points
are measured in units of 0.00001 radian.
.I Latitude
is counted positive to the north and
.I longitude
positive to the west.
.PP
The patches are ordered lexicographically by 
.I patchlatitude
then
.IR patchlongitude .
A printable
index to the first segment of each patch
in a file named
.I map
is kept in an associated file named
.IB map .x\fR.\fP
Each line of an index file contains 
.I patchlatitude,
.I patchlongitude
and the byte position 
of the patch
in the map file.
.SH "SEE ALSO"
map(7), map(3)