I have been intrigued for quite a while by all the GeoReferencing of Web sites and blog entries that has been going on for a while, but have not managed to get my site listed in any of the directories, because of my strong desire to use Dublin Core for all of my metadata—which none of the geographic directories have seen fit to use.
Now I know why. None of the examples on how to structure DC GeoReferencing metadata are completely clear on specifics, or the concept. The two primary methods, TGN and DCMIPOINT, are not even clearly defined on the Dublin Core Web site. Through much experimentation, thinking, contacting The Getty, and still more thinking, I have arrived at two conclusions. One: That a better GeoReferencing Scheme to use in the real world is GeoTags, and Two: That Dublin Core can also be used, but only when formatted as I have done on my site, and excerpted below:
<link rel="schema.DC" href="http://purl.org/dc/terms/" title="DCMES plus DCMI recommended qualifiers" /> <meta name=DC.Coverage.spatial" scheme="DCMIPOINT" content="name=Foster City; north=+37.5500;east=-122.2667; projection=WGS-84;units=signed decimal degrees; elevation=1.5;zunits=m" /> <meta name="DC.Coverage.spatial" scheme="TGN" content="id="2011419; name=Foster City; hierarchy=San Mateo county, California, United States, North and Central America, World; type=inhabited place" /> <link rel="schema.GEO" href="http://geotags.com/geo/geotags2.html" title="Geo Tags for HTML Resource Discovery" /> <meta name="GEO.position" content="+37.5500;-122.2667;1.5" /> <meta name="GEO.placename" xml:lang="en-US" content="Foster City" /> <meta name="GEO.region" content="US-CA" />
The details of the reasoning behind my choices, and the specifics of the above content, are far too detailed for a blog entry, and will have to wait until I have the time to write up an article on my research and thinking. I believe, however, that the verbosity of my metadata, and a reference to the appropriate documentation (such as The Getty’s entry for Foster City and the GeoTags documentation, will allow you to see that this structure at least makes sense.
A few quick comments should be made now, though:
- Yes, I have included duplicate data in two formats.
- Geo Tags is used because it is supported by georeferencing directories now, and becauseits
regiontag can be parsed and mapped to a country and state more easily than TGN’s hierarchy string.
- Dublin Core is used because it is the right format for important metadata, and the keywords for all the tidbits of data reduce ambiguity.
- The Dublin Core orginization should update its documentation to eliminate the confusion that has stalled its adoption by Web authors.
Note that because of the cited lack of documentation, a few of the minor details still raise questions for me. For example, although my use of “signed decimal degrees” conforms with documentation on the Dublin Core site as well as being a recognized mapping industry phrase for the representation of coordinates It seems to me there should be an abbreviation for the type of units, and one with no whitespace.