Should be set to the size, in seconds, of
the largest feature which the decimation routine will eliminate. Usually
this should be no higher that 3600 seconds (1 degree). A setting of 1
second will include all features since raw map coordinates are in integer
numbers of seconds. Most features on the map appear to be on the order
of thirty seconds. The decimation algorithm operates by combining as
many line segments smaller than precision as possible such that their
total vector length is still less than Precision into a single line segment.
This will tend to eliminate features smaller than Precision and small
islands may be reduced to a segment of zero length.
Remember that the map files are greatly compressed and when
read into memory the map will be much larger. It is best to start at lower
resolution with fewer features and build up than to attempt to read in the
entire map at full resolution. One must use less resolution when looking
at large areas and higher resolution when zooming in. This will also
improve the drawing time for the map.