1 058b0118 2005-01-03 devnull .TH MAP 7
 2 058b0118 2005-01-03 devnull .SH NAME
 3 058b0118 2005-01-03 devnull map \- digitized map formats
 4 058b0118 2005-01-03 devnull .SH DESCRIPTION
 5 058b0118 2005-01-03 devnull Files used by
 6 058b0118 2005-01-03 devnull .IR  map (7)
 7 058b0118 2005-01-03 devnull are a sequence of structures of the form:
 8 058b0118 2005-01-03 devnull .PP
 9 058b0118 2005-01-03 devnull .EX
10 058b0118 2005-01-03 devnull struct {
11 058b0118 2005-01-03 devnull 	signed char patchlatitude;
12 058b0118 2005-01-03 devnull 	signed char patchlongitude;
13 058b0118 2005-01-03 devnull 	short n;
14 058b0118 2005-01-03 devnull 	union {
15 058b0118 2005-01-03 devnull 		struct {
16 058b0118 2005-01-03 devnull 			short latitude;
17 058b0118 2005-01-03 devnull 			short longitude;
18 058b0118 2005-01-03 devnull 		} point[n];
19 058b0118 2005-01-03 devnull 		struct {
20 058b0118 2005-01-03 devnull 			short latitude;
21 058b0118 2005-01-03 devnull 			short longitude;
22 058b0118 2005-01-03 devnull 			struct {
23 058b0118 2005-01-03 devnull 				signed char latdiff;
24 058b0118 2005-01-03 devnull 				signed char londiff;
25 058b0118 2005-01-03 devnull 			} point[\-n];
26 058b0118 2005-01-03 devnull 		} highres;
27 058b0118 2005-01-03 devnull 	} segment;
28 058b0118 2005-01-03 devnull };
29 058b0118 2005-01-03 devnull .EE
30 058b0118 2005-01-03 devnull where
31 058b0118 2005-01-03 devnull .B short
32 058b0118 2005-01-03 devnull stands for 16-bit integers and there is no padding within or between
33 058b0118 2005-01-03 devnull .BR structs .
34 058b0118 2005-01-03 devnull Shorts are stored in little-endian order, low byte first.
35 058b0118 2005-01-03 devnull To assure portability,
36 058b0118 2005-01-03 devnull .I map
37 058b0118 2005-01-03 devnull accesses them bytewise.
38 058b0118 2005-01-03 devnull .PP
39 058b0118 2005-01-03 devnull Fields
40 058b0118 2005-01-03 devnull .L patchlatitude
41 058b0118 2005-01-03 devnull and
42 058b0118 2005-01-03 devnull .L patchlongitude
43 058b0118 2005-01-03 devnull tell to what
44 058b0118 2005-01-03 devnull 10-degree by 10-degree
45 058b0118 2005-01-03 devnull patch of the earth's surface a segment belongs.
46 058b0118 2005-01-03 devnull Their values range from \-9 to 8 and from \-18 to 17,
47 058b0118 2005-01-03 devnull respectively, and indicate the coordinates of the
48 058b0118 2005-01-03 devnull southeast corner of the patch in units of 10 degrees.
49 058b0118 2005-01-03 devnull .PP
50 058b0118 2005-01-03 devnull Each segment of
51 058b0118 2005-01-03 devnull .RB | n |
52 058b0118 2005-01-03 devnull points is connected; consecutive segments
53 058b0118 2005-01-03 devnull are not necessarily related.
54 058b0118 2005-01-03 devnull Latitude and longitude
55 058b0118 2005-01-03 devnull are measured in units of 0.0001 radian.
56 058b0118 2005-01-03 devnull If
57 058b0118 2005-01-03 devnull .B n
58 058b0118 2005-01-03 devnull is negative, then
59 058b0118 2005-01-03 devnull differences to the first and succeeding points
60 058b0118 2005-01-03 devnull are measured in units of 0.00001 radian.
61 058b0118 2005-01-03 devnull Latitude is counted positive to the north and
62 058b0118 2005-01-03 devnull longitude positive to the west.
63 058b0118 2005-01-03 devnull .PP
64 058b0118 2005-01-03 devnull The patches are ordered lexicographically by
65 058b0118 2005-01-03 devnull .L patchlatitude
66 058b0118 2005-01-03 devnull then
67 058b0118 2005-01-03 devnull .LR patchlongitude .
68 058b0118 2005-01-03 devnull A printable
69 058b0118 2005-01-03 devnull index to the first segment of each patch
70 058b0118 2005-01-03 devnull in a file named
71 058b0118 2005-01-03 devnull .I data
72 058b0118 2005-01-03 devnull is kept in an associated file named
73 058b0118 2005-01-03 devnull .IB data .x\f1.
74 058b0118 2005-01-03 devnull Each line of an index file contains
75 058b0118 2005-01-03 devnull .L patchlatitude,
76 058b0118 2005-01-03 devnull .L patchlongitude
77 058b0118 2005-01-03 devnull and the byte position
78 058b0118 2005-01-03 devnull of the patch
79 058b0118 2005-01-03 devnull in the map file.
80 058b0118 2005-01-03 devnull Both the map file and the index file are ordered by
81 058b0118 2005-01-03 devnull patch latitude and longitude.
82 058b0118 2005-01-03 devnull .SH "SEE ALSO"
83 d32deab1 2020-08-16 rsc .MR map (7)
84 058b0118 2005-01-03 devnull .br
85 058b0118 2005-01-03 devnull The data comes from the World Data Bank I and II and
86 058b0118 2005-01-03 devnull U.S. Government sources: the Census Bureau, Geological
87 058b0118 2005-01-03 devnull Survey, and CIA.