Smfilter is a seamark preprocessor for rendering software for OSM, such as Osmarender or Mapnik.
It is used to process
several seamark specific tags which describe a seamark's properties.
In a sea chart those properties are visually displayed through lines,
arcs, and probably colors. This makes charts more intuitive for mariners.
Those special properties are mainly sectors of light visibility (see for example
the Needles Lighthouse).
Smfilter reads and parses OSM files and generates such virtual nodes and ways of seamarks which are further processed by Osmarender (or Mapnik). The output is again an OSM file which contains all input plus the additionally generated nodes and ways.
Smfilter is available for download here. It is based an libhpxml which is included in the package.
Further documentation is found in the smfilter(1) manpage which is included in the package.
Smfilter does neither validate the XML file nor the semantics of the OSM data. Thus, smfilter may behave unexpected if the input file is not well-formed.
smfilter is developed and maintained by Bernhard R. Fischer, 2048R/5C5FFD47 <email@example.com>.
smfilter is released under GNU GPLv3.