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Re: Best Practice for encoding spatial coverage

From: Andrea Perego <andrea.perego@jrc.ec.europa.eu>
Date: Thu, 18 Jun 2015 01:52:59 +0200
Message-id: <CAHzfgWD8UHJe8HjuVwWsr3_i1SYOEAjUotwr9OsXb-qSasCSyQ@mail.gmail.com>
To: Frans Knibbe <frans.knibbe@geodan.nl>
Cc: SDW WG Public List <public-sdw-wg@w3.org>
Hi, Frans.

Looking at what is currently used in the Web and by Web developers:

1. schema.org has a specific property fox bboxes - i.e., schema:box

The bbox is encoded as follows:

"A box is the area enclosed by the rectangle formed by two points. The
first point is the lower corner, the second point is the upper corner.
A box is expressed as two points separated by a space character."

The axis order used is lat / long, as said in the description of
schema:GeoShape (http://schema.org/GeoShape), which also describes the
encoding used:

"The geographic shape of a place. A GeoShape can be described using
several properties whose values are based on latitude/longitude pairs.
Either whitespace or commas can be used to separate latitude and
longitude; whitespace should be used when writing a list of several
such points."

2. GeoJSON includes a "member" bbox to be used to "include information
on the coordinate range for geometries, features, or feature
collections" - see:


The encoding used is as follows:

"The value of the bbox member must be a 2*n array where n is the
number of dimensions represented in the contained geometries, with the
lowest values for all axes followed by the highest values."

Maybe we can build upon these examples.


On Wed, Jun 17, 2015 at 11:53 AM, Frans Knibbe <frans.knibbe@geodan.nl> wrote:
> Hello all,
> Is it OK to try to venture in to the domain of best practices already? I
> wonder if we can try our hands at the following issue:
> I have just had a talk with a web developer on the best way of making the
> extent of a spatial data set known, in a Linked Data context. It is useful
> to know the spatial extent of a data set because that way a map can be
> zoomed in on the right patch of Earth.
> I think an obvious predicate for making the extent known is dcterms:spatial
> (Spatial Coverage). That should point to a dcterms:Location, which can have
> a geometry. So an option would be to encode the extent as a WKT polygon,
> according to GeoSPARQL semantics. But that would not be the most
> webdeveloper-friendly way of making the extent known.  The usual way of
> setting a map extent involves knowing the minimum and maximum values for X
> and Y. So a question is: what would be the best way to publish the minimum
> and maximum X and Y? There are usable vocabularies for publishing point
> coordinates, so one could think of recommending to publish two points (lower
> left corner and upper right corner). Perhaps there are standard vocabularies
> available that define the concepts of 'minimum' and 'maximum' and 'x' and
> 'y'?
> I should note that this issue relates to the Spatial metadata requirement.
> Greetings,
> Frans
> --
> Frans Knibbe
> Geodan
> President Kennedylaan 1
> 1079 MB Amsterdam (NL)
> T +31 (0)20 - 5711 347
> E frans.knibbe@geodan.nl
> www.geodan.nl
> disclaimer

Andrea Perego, Ph.D.
Scientific / Technical Project Officer
European Commission DG JRC
Institute for Environment & Sustainability
Unit H06 - Digital Earth & Reference Data
Via E. Fermi, 2749 - TP 262
21027 Ispra VA, Italy


The views expressed are purely those of the writer and may
not in any circumstances be regarded as stating an official
position of the European Commission.
Received on Wednesday, 17 June 2015 23:53:48 UTC

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