MAP(7)

✨ NAME ✨

map — digitized map formats

okay so welcome to MAP(7) from the Miscellaneous Information Manual, bestie — this is the whole vibe for map, and it is lowkey iconic for a format page 💅

🌸 DESCRIPTION 🌸

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. 🫶

The patchlatitude and patchlongitude fields tell you which 10-degree by 10-degree patch of the earth’s surface a segment belongs to. 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 — and yeah, the source sentence literally trails off right there 😭 — 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 — the original text drops a word here too, no cap 😭 — 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. 💖

🦋 SEE ALSO 🦋

• map(7)
• The data comes from the World Data Bank I and II and U.S. Government sources: the Census Bureau, Geological Survey, and CIA. 👑

That’s the whole MAP(7) page, bestie. The footer line in this copy is just MAP(7) — no separate source/version or date info beyond that, so that’s the cute sign-off. 💖🎀