[Gdal-dev] IntegerList datatype

[nida Khan]

Hi,

Thanx for your reply.
I'm very hopeful from your reply, please do let me know if you have success
either in completing python scripting or modifying OGR.

I really appreciate your help
kind regards
Nida.

>
> Nida,
>
> It is a fundamental flaw in the NTF readers in OGR that they don't
assemble
> the geometries for polygons from the component line strings.  I tried the
> following python script using OGR on BL2000 data and it sort of worked,
but
> any of the long geom_id_of_link lists are truncated and ended with ... so
the
> data you have in the database now can never be properly assembled into
> polygons.
>
> The script can be run against a raw NTF file but in it's currently
unfinished
> state it does not actually write the assembled features anywhere, so it
isn't
> in a useful state yet.  Think of this as an experiment on my part in using
> Scripting for processing features.
>
> I will look at completing the script tonight, but no promises.
Alternatively
> I may just fix the NTF reader to do the same thing internally.
>
> Best regards,
>
> --
> ---------------------------------------+----------------------------------
----
> I set the clouds in motion - turn up   | Frank Warmerdam,
warmerdam at pobox.com
> light and sound - activate the windows | http://pobox.com/~warmerdam
> and watch the world go round - Rush    | Geospatial Programmer for Rent
>
> import osr
> import ogr
> import string
>
> #ds = ogr.Open( '/u/data/ntf/bl2000/HALTON.NTF' )
> ds = ogr.Open( 'PG:dbname=test', update = 1 )
>
> layer_count = ds.GetLayerCount()
>
>
############################################################################
#-
> # Establish access to the line and polygon layers.  Eventually we
shouldn't
> # hardcode this.
>
> line_layer = ds.GetLayer(0)
> poly_layer = ds.GetLayer(1)
>
>
############################################################################
#
> # Read all features in the line layer, holding just the geometry in a hash
> # for fast lookup by GEOM_ID.
>
> lines_hash = {}
>
> feat = line_layer.GetNextFeature()
> geom_id_field = feat.GetFieldIndex( 'GEOM_ID' )
> tile_ref_field = feat.GetFieldIndex( 'TILE_REF' )
> while feat is not None:
>      geom_id = feat.GetField( geom_id_field )
>      tile_ref = feat.GetField( tile_ref_field )
>
>      if not lines_hash.has_key( tile_ref ):
>          lines_hash[tile_ref] = {}
>
>      sub_hash = lines_hash[tile_ref]
>      sub_hash[geom_id] = feat.GetGeometryRef().Clone()
>
>      feat.Destroy()
>
>      feat = line_layer.GetNextFeature()
>
> print 'Got %d lines.' % len(lines_hash)
>
>
>
############################################################################
#
> # Read all polygon features.
>
> feat = poly_layer.GetNextFeature()
> link_field = feat.GetFieldIndex( 'GEOM_ID_OF_LINK' )
> tile_ref_field = feat.GetFieldIndex( 'TILE_REF' )
>
> while feat is not None:
>      tile_ref = feat.GetField( tile_ref_field )
>      link_list = feat.GetField( link_field )
>
>      # If the list is in string form we need to convert it.
>      if type(link_list).__name__ == 'str':
>          colon = string.find(link_list,':')
>          items = string.split( link_list[colon+1:-1], ',' )
>          link_list = []
>          for item in items:
>              try:
>                  link_list.append(int(item))
>              except:
>                  print 'item failed to translate: ', item
>
>      link_coll = ogr.Geometry( type = ogr.wkbGeometryCollection )
>      for geom_id in link_list:
>          geom = lines_hash[tile_ref][geom_id]
>          link_coll.AddGeometry( geom )
>
>      try:
>          poly = ogr.BuildPolygonFromEdges( link_coll )
>          print poly.ExportToWkt()
>          feat.SetGeometryDirectly( poly )
>      except:
>          print 'BuildPolygonFromEdges failed.'
>
> #    poly_layer.SetFeature( feat )
>      feat.Destroy()
>
>      feat = poly_layer.GetNextFeature()
>
>
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