gshhg_dp − Line reduction using the Douglas-Peucker algorithm
gshhg_dp input.b tolerance output.b [−v]
reads the binary coastline (GSHHS) or political boundary or
river (WDBII) files and and reduces the complexity of the
line by applying the Douglas-Peucker algorithm. It
automatically handles byte-swabbing between different
GSHHS or WDBII binary data file as distributed with the GSHHG data supplement. Any of the 5 standard resolutions (full, high, intermediate, low, crude) can be used.
tolerance is maximum mismatch in km. The larger the value the more reduction will take place.
The reducted data set.
Reports progress and statistics while running.
To simplify the full GSHHS data set with a custom tolerance of 2 km, try
gshhg_dp gshhs_f.b 2 gshhs_2km.b
Douglas, D. H., and T. K. Peucker, Algorithms for the reduction of the number of points required to represent a digitized line of its caricature, Can. Cartogr., 10, 112-122, 1973.
This implementation of the D-P algorithm has been kindly provided by Dr. Gary J. Robinson, Environmental Systems Science Centre, University of Reading, Reading, UK (email@example.com); his subroutine forms the basis for this program.
GMT(1), gshhg(1), gshhgtograss(1)