INTERNET-DRAFT Vancouver Webpages
draft-daviel-html-geo-tag-00.txt March 1999 (Expires Sept. 1999)
Geographic registration of HTML documents
Status of this Memo
This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026.
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Abstract
This memo describes a method of registering HTML documents with a
specific geographic location through means of embedded META tags. The
content of the META tags gives the geographic position of the
resource described by the HTML document in terms of Longitude,
Latitude and optionally Elevation in a simple, machine-readable
manner. This information may be used for automated resource discovery
by means of an HTML indexing agent or search engine.
1. Introduction
Many resources described by HTML documents on the World-Wide-Web are
associated with a particular place on the Earth's surface. While
resource discovery on the Web has thus far focussed on document title
and open-text keyword searching, in these cases it may be beneficial
to facilitate geographic searching. Examples of this kind of resource
include pages describing restaurants, shipwrecks, wildlife refuges
etc.
2. Coordinate Systems
Resource positions on the Earth's surface should be expressed in
degrees East of Longitude, degrees North of Latitude as signed
decimal numbers. The number of decimal places given should reflect
the precision of the coordinates, with zeroes being used as
placeholders. A decimal point is optional where the precision is
less than one degree. Where the precision of the coordinates is such
that the datum used is significant, typically more precise than one
kilometre distance, positions should be converted to the WGS 84 datum
[3]. Elevations, if given, should be in metres above datum. Positions
given by a GPS set [4] with datum set to "WGS 84" will in most cases
be adequate, of the order of 200 metres accuracy.
3. Implementation
HTML markup should be added to the document in the form of a META
statement. This should be placed in the document head in accordance
with the HTML 4 specification [1]. The identifier "geo.position" is
used for Longitude, Latitude and optionally Elevation data. The
identifier "geo.placename" is used for a free text representation of
the position, for example "city, province" or "town, county, state".
The identifier "geo.country" is used for the 2-character country code
from ISO 3166 [5].
It is anticipated that the "geo.placename" tag be used for resource
recognition, rather than resource discovery, due to possible
ambiguities in naming convention, language, word ordering and
placename duplicates.
Although the HTML specification [1] states that the name field is in
general case-sensitive, these "geo" tags should be recognized by
compliant agents regardless of case. Coordinates should be ordered
(Longitude, Latitude [,Elevation]) corresponding to the map
coordinates (x, y [,z]) as is common cartographic practice.
4. Examples
<META NAME="geo.position" content="-123.84,48.54,115">
describes a resource 115 metres above datum, at position 123.84
degrees West, 48.54 degrees North, while
<META NAME="geo.position" content="60,-10">
describes a resource at position 60 degrees West, 10 degrees South.
<META NAME="geo.placename" content="London, Ont">
<META NAME="geo.country" content="ca">
describes a resource in London, Ontario, Canada while
<META NAME="geo.placename" content="London">
<META NAME="geo.country" content="gb">
describes a resource in London, England (Great Britain).
5. Applicability
As stated in the introduction, certain HTML documents may be
associated with a geographic position, while other documents are not.
For proper use of the "geo" tags as described in this draft, the
resource described in an HTML document should be associated with a
particular location for the lifetime of the document. The tags may
be properly used to describe, for instance, a retail store, a
mountain peak or a railway station but not an oil company, river,
aircraft or mathematical theory.
The geographic position given is associated with the resource
described by the HTML document, not with the physical location of the
document [2], or the location of the company responsible for
publishing or hosting the document. Thus, in some cases the country
code used in "geo.position" may differ from the country code forming
part of the host address in the document URL.
6. Further information
Further information may be obtained at http://vancouver-webpages/geo/
7. Security Considerations
This draft raises no security issues.
8. References
[1] Raggett, Le Hors, Jacobs, "HTML 4.0 Specification",
http://www.w3.org/TR/1998/REC-html40-19980424, W3C, April 1998
[2] Davis et al., "A Means for Expressing Location Information in
the Domain Name System", RFC 1876, January 1996
See also DNS LOC.
[3] United States Department of Defense; DoD WGS-1984 - Its
Definition and Relationships with Local Geodetic Systems;
Washington, D.C.; 1985; Report AD-A188 815 DMA; 6127; 7-R-
138-R; CV, KV;
[4] ARINC Research Corporation, "Navstar GPS Space Segment /
Navigation User Interfaces", IRN-200C-002, September 1997
Related pages: USCG GPS page
[5] International Organization For Standardization / Organisation
Internationale De Normalisation (ISO), "Standard ISO 3166-1988:
Codes for the Representation of Names of Countries", 1988.
(e.g. iso3166-countrycodes.txt
9. Author's Address
Andrew Daviel
Vancouver Webpages, Box 357
185-9040 Blundell Rd
Richmond BC
V6Y 1K3
Canada
Tel. (604)-377-4796
Fax. (604)-270-8285
mailto:andrew@vancouver-webpages.com