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The person who is best fitted to respond to this is Betsy Mangan but I think
she's on vacation so I'll send in some brief stopgap info.
These fields are some of the new fields that were created in USMARC due to the
U.S. Federal Geographic Data Committee's Content Standard for Digital Geospatial
Data - you can get a copy at:
http://fgdc.er.usgs.gov/
 
Betsy worked very hard on getting these into USMARC; she presented them at a
MARBI meeting.  Currently a task force (for cataloging spatial data in digital
form) of the AngloAmerican Cataloguing Committee for Cartographic Materials -
which latter is working on a second ed. of Carto. Mtls, a Manual of Interp. for
AACR2 - is working on putting together guidelines/explanations for these fields.
 Briefly, the "outer ring" and "exclusion ring" are for those situations when a
cataloger has, instead of bounding-box coordinates (already in 034 and also in
255$c), a set of points that constitute a polygon; the polygon may be any shape.
 The exclusion-ring points are for those times when the cataloger is describing
a spatial-data set that has an area that is not being described - for example,
if you had an area with a lake, and the dataset did not have any data for the
lake, then the lake would be marked with exclusion-ring polygon.
 
 
Mary Larsgaard
UCSB