The color of the coastline.
defaut value is 0 => black
COAST_THICK
The thick of the trait to trace continents
By default, it is 1.
YSEUIL
See XSEUIL
XSEUIL
To eliminate segments of coasts which are to big (which link points which can
be close on the sphere but distant on the drawing). We delete all segments
whose the size surpass the size of the window following X/XSEUIL. By default,
XSEUIL=5. But it can be to big if we do a big zoom or a little one for some
projections... We specify it the keyword thanks to this keyword!