[Talk-us] hyrdography imports

Mike N. niceman at att.net
Wed Feb 10 15:48:35 GMT 2010

> any way the importer can
> a) go back and fix all the millions of duplicated nodes
> b) not do it in future?

  I'm working on both points -

a) Happens in several cases:
  1. At the joining of streams to waterbodies.  The duplicate happens 
because data comes from 2 separate sources (Flowlines and Waterbodies / 
Areas).   There needs to be a higher level view to combine them.  The number 
of duplicates is relatively small.
  2. NHD features are placed into multiple NHD 'sub-basin extracts'. 
Those could be eliminated at OSM conversion time if the conversion scripts 
were to have access to all features previously imported.   This can result 
in many duplicates.
   3.  Adjoining area types from NHD do not share nodes, but should.   I was 
able to cobble together a manual Perl script to fix this up as features are 
imported, but it's not a good general solution.

b.)  All current scripts I know of require significant rework, short of 
importing the NHD into a local GEO database, then exporting it to remove 
duplicate nodes.

 Should we halt all US Hydro import work until this is resolved?


More information about the Talk-us mailing list