mapnik/mapnik — comment on commit 56aeae1b52bf3c9b5f6bffef5c77a927699031ff
File:  line 0
By springmeyer:

It's not used anywhere for rendering, which is why being made an optional depdency as many distros lag in their boost versions. The idea behind wkb/wkt/json output support is for programmatically working with features for calling applications that need it. Nothing in core uses this yet.