Date Long time ago (about 1991)
By Lars Aronsson <aronsson@lysator.liu.se>
FTP lysator.liu.se (130.236.254.1)
File pub/geography/wdb2-README
The terminology used here is my own. The facts here presented are
partly taken from documents that come with Brian Reid's compacted
version of WDB II and partly deduced from my own browsing through the
map data files.
The files called wdb2-something are parts of the World Databank II
compiled by USAs Central Intelligence Agency (CIA). The original
databank consists of almost six million geographic coordinates and
occupies about 130 megabytes of disk in uncompressed form. It is
available from the U.S. Government and is in the public domain. The
coordinates are connected by lines to form coast contours, islands,
lakes (CIL), political boundaries (BDY), and rivers (RIV).
The maps cover one continent each and they each consist of three
files: cil.dat, bdy.dat, and riv.dat.
Each file is structured as a large set of 20 bytes ASCII records (plus
one linefeed character per record). The records are grouped to
geographic objects each consisting of one head record and a sequence
of coordinate records. The head record among other things tell the
number of coordinate records to follow. The coordinate records, each
containing one geographic coordinate, form the object when connected
by straight lines in the sequence given.
If a geographic object is supposed to be a closed path, as is the case
for island and lake contours, then the first coordinate of that object
is also explicitly given as the last coordinate.
A head record has the following format:
4114666 1 536 0
aaaaaaabbccccccddddd
It consists of a seven digit object identifier field (a), a two digit
object type field (b) the meaning of which is different for the three
different kinds of files, a six digit field (c) telling the number of
following coordinate records, and a five digit field (d) which always
contains a zero in head records.
The different meanings of the (b) field are: In "Boundary" (BDY) files:
1 Demarcated or delimited boundary
2 Indefinite or in Dispute
3 Other line of separation of sovreignty on land
In "Coast, Islands and Lakes" (CIL) files
1 Coast, islands and lakes that appear on all maps
2 Additional major islands and lakes
3 Intermediate islands and lakes
4 Minor islands and lakes
6 Intermittent major lakes
7 Intermittent minor lakes
8 Reefs
9 Salt pans -- major
10 Salt pans -- minor
13 Ice Shelves -- major
14 Ice Shelves -- minor
15 Glaciers
In "Rivers" (RIV) files
1 Permanent major rivers
2 Additional major rivers
3 Additional rivers
4 Minor rivers
5 Double lined rivers
6 Intermittent rivers -- major
7 Intermittent rivers -- additional
8 Intermittent rivers -- minor
10 Major canals
11 Canals of lesser importance
12 Canals -- irrigation type
Coordinate records (two in sequence given here) have the following
format:
175958S 231737E 1
18 011S 231750E 2
eeffgghiiijjkklddddd
They consist of a two digit latitude degrees field (e), a two digit
latitude minutes field (f), a two digit latitude seconds field (g), a
one character ('S' or 'N') latitude direction field (h), a three digit
longitude degrees field (i), a two digit longitude minutes field (j),
a two digits longitude seconds field (k), a one character ('W' or 'E')
longitude direction field (l), and finally a five digit sequence
number field (d).
The (d) field in the coordinate record has the same position and
length as in the head record. The (d) field of the first coordinate
record within each geographic object has the value 1 (one). The
following coordinate records sequentially count up to and including
the value given in the (c) field of the head record.
Note that coordinates are given as degrees-minutes-seconds and that
the fields (f, g, j, k) therefore will assume values " 0" thru "59".
An obvious use of the object identifier field (a) in the head record
would be to use as a key to a database lookup for its name (and other
interesting data that might be associated with a geographic object).
However, I have not found any such names database.