These are the files for the sailboat navigation homework. There are
three different kind of files and some visualizations of those files.

Speeds for different angles and winds
-------------------------------------

The files named 6kt, 8kt, ... , 20kt tell how fast the sailboat can
move in different directions in different winds. for example an
excerpt form the file 12kt:

---------------
...
9.0 1.64816567182
10.0 1.83129519091
11.0 2.01442471
12.0 2.19755422909
13.0 2.38068374818
14.0 2.56381326727
15.0 2.74694278637
16.0 2.93007230546
17.0 3.11320182455
18.0 3.29633134364
19.0 3.47946086273
20.0 3.66259038182
21.0 3.84571990091
....
--------------

tells that when the wind speed is 12kt, the boat can sail
3.29633134364 sea miles per hour to the direction 16 angles (angle 0
means directly against the wind and the wind is always assumed to blow
from east to west.). The angles listed are 0.0, 1.0, 2.0, ..... 360.0.
NB! Speed for 0 is same as speed for 360.

Speed for fractional angles is supposed to be linearly
interpolated. For example, the speed for the angle 12.3 is 
0.7*2.19755422909 + 0.3*2.38068374818 = 2.252493084817.

The picture pdg.png shows these speeds in a picture. This picture is
called a polar diagram.

Islands files
-------------

The ils-files define the islands of the sea.  There are always 10
islands per file. (Actually the coordinates of the islands may overlap
so that there often is less than 10 real islands.)  The islands are
simply defined as polygons, and each polygon is just a set of six
xy-coordinates that define the vertices of the polygon. In the beginning
of the ils-files there are lines that define the borders of the
sailing area.  The very first line of the file incidentally defines
the dimensions of the sailing area. All the measurements are supposed
to be in sea miles. The sailing area for all the ils-files is the same.
The origin of the coordinate system is meant to be in lower left corner.

For example the file 51.ils starting: 

----------------------------
00.0 100.0
100.0 0

0 0
0 100.0

0 100.0
100.0 100.0

100.0 0
0 0

80.8818325322 63.1521768814
84.4759294382 45.6154025187
54.1843024826 64.082105914
63.9094450496 35.5142336223
68.9340436084 69.7615864272
63.8778540362 91.2619263273
80.8818325322 63.1521768814

6.45989906132 44.9840189413
8.03701082567 82.9168573814
11.1932971421 71.3385260901
16.7361989793 57.0586758257
0 66.2690886807
.....

defines a sailing area of 100.0 x 100.0 sea miles. The format is so
defined that consecutive xy-coordinates define lines. When sailing,
the only hard constraint is not to cross any lines, so it is possible
to forget about the islands, and just consider the whole set of lines,
no matter in which island they belong to.

The task files
--------------

The sailing task files are just a list of three xy-coordinate pairs.
The first line is the starting point, the second line is a waypoint that
has to be reached and the third is again the same as the starting point.
The numbers in the names of the task files refer to the ils-files of the same number. For example the file task_67:
-----
80 10
20 90
80 10
-----

sets the task of sailing from point (80, 10) to the point (20, 90) and back.

The tasks and the associated islands can be found in corresponding
png-picture files.
