updated Shapefile Flattening tool

[Bruce Raup]

Dear GLIMS affiliates,

I have made some improvements to the "shapefile flattening" tool, 
available under

http://glims.colorado.edu/tools/

The changes are listed below.  The full purposed of this tool is described 
at the above URL.  In brief, the tool converts shapefiles that represent 
glaciers and internal rock outcrops as multi-part polygons (with the holes 
representing the rocks) to shapefiles that represent the rocks with 
separate polygons.  GLIMS represents internal rock outcrops with separate 
polygons so that they can have their own attributes.

Modifications are:

- if the "category" attribute does not exist in the uploaded shapefile(s),
  it is automatically added.  That field is then populated with
  "glac_bound" for the boundaries and "intrnl_rock" for the "holes".  (This
  might fix your problem, Tobias.)

- I have seen a number of cases where shapefiles containing multi-part
  polygons (polygons with "holes") are incorrectly structured.  That is,
  the outer-most ring (polygon) is a sub-part, and one of the "holes" is
  actually the top-level polygon.  So, to deal with this, I have added an
  option to the flattening tool to identify the top-level polygon (the
  glacier boundary) by maximum vertex count, rather than trusting the
  structure of the shapefile.  To activate this option, check the checkbox
  under the filename field.

Just a reminder:  it's best to have assigned GLIMS IDs (or at least some
sort of unique ID) to the polygons in your multi-part shapefile before
using this tool on it.  This ID is what will tie the boundaries to the
rocks after flattening.

Please let me know if you have any problems (or feature requests) with this
tool.

Best regards,
Bruce

-- 
Bruce H. RAUP
National Snow and Ice Data Center
University of Colorado
449 UCB,  Boulder, CO 80309
Phone:  303-492-8814
http://cires.colorado.edu/~braup/