----------------------------Original message----------------------------
 Holly Peacock <HEP241T@SMSVMA> writes
 
 >To some people this may be an unintelligent question, but I can't
 >stand it anymore. With the talk of Format Integration Phase 2 there
 >has been mention of a phrase that I have never heard when discussing
 >the maps changes. What is "g-ring" information? The catalogers here
 >asked me this after they attended a video conference on FI2 and while
 >we had some fun coming up with possibilities I never found out what it
 >means/refers to. I have heard it mentioned when discussing the
 > 034 and 255 field which deals with scale in cataloging. Is there a
 >brief definition that someone can give?
 >
 >Thanks,
 >
 >Holly Peacock
 >Government Documents/Maps
 >Duane G. Meyer Library
 >Southwest Missouri State University
 >Springfield, MO 65804
 >417-836-4534
 >[log in to unmask]
 >
 
 The term "g-ring" is from the Spatial Data Transfer Standard (SDTS), also
 known as Federal Information Processing Standard Publication 173.  From
 the standard:
 
 Ring: a sequence of nonintersecting chains or strings and (or) arcs, with
 closure.  A ring represents a closed boundary, but not the interior area
 inside the closed boundary.
 
 G-ring: A ring created from strings and (or) arcs.  (The "G" stands for
 "geometry only".  Strings are used more commonly than are arcs.)
 
 For completeness:
 
 String: A connected nonbranching sequence of line segments specified as
 the ordered sequence of point between those line segments.
 
 Arcs: A locus of points that forms a curve that is defined by a
 mathematical expression.
 
 What did he say?
 
 Basically, a g-ring is the coordinates for a set of points that, when
 connected, form a closed loop.
 
 Why would we care?
 
 The Federal Geographic Data Committee's (FGDC's) metadata standard for
 geospatial data allows persons using the standard to provide a coordinate
 (longitude-latitude) description (or g-ring) of the outline of their
 digital maps or other geospatial data.  For example, if the State of
 Missouri digitized the state highway map and documented these data using
 the metadata standard, they could provide the coordinate outline of the
 state as part of the metadata.
 
 This information can then be used by patrons to help them limit their
 searches and find data of interest.  In addition to entering keywords and
 other textual criteria for searches, a patron could be presented a map and
 be invited to draw a ring around the geographic area of interest.  For
 example, a patron might be presented a map of the United States as part of
 a computer interface to a catalog or clearinghouse.  The patron, in
 addition to entering keywords and other textual or numeric parameters for
 a search, could draw an outline approximating the State of Missouri (or a
 county, or a watershed, or whatever) as part of the search criteria.  The
 system would match the patron's coordinate outline (g-ring) with the g-rings
 in the metadata records to help find records of interest.
 
 The FGDC decided to use pre-existing terminology, such as those
 provided by SDTS, whenever possible, and so inherited the term "g-ring".
 This terminology, in turn, probably was transferred to the library
 community through the collaboration between the FGDC and the Library of
 Congress during the development of the metadata standard.
 
 For more information about the metadata standard and National Geospatial
 Data Clearinghouse: http://www.fgdc.gov,
 or request a copy of the metadata workbook by email from [log in to unmask] or
 by facsimile from 703.648.5755 (be sure to include your postal mailing
 address in your request!)
 
 For more information about the Spatial Data Transfer Standard:
 http://mcmcweb.cr.usgs.gov/~sdts
 
 MADomaratz
 FGDC Secretariat
 [log in to unmask]