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Re: updates to the Best Practice document

From: Jeremy Tandy <jeremy.tandy@gmail.com>
Date: Thu, 08 Sep 2016 09:50:19 +0000
Message-ID: <CADtUq_09F3NXyYhGAoSDAzF=gPMFyL8oBDB1X00N7+BkG0bEMg@mail.gmail.com>
To: Simon.Cox@csiro.au, public-sdw-wg@w3.org
All- I've tried to incorporate some of the useful text cited by Simon. I've
also taken the opportunity to update the definition of coverage in the
glossary.

On Thu, 8 Sep 2016 at 07:24 Jeremy Tandy <jeremy.tandy@gmail.com> wrote:

> Hi Simon- That's useful ... what's the copyright associated with the ISO
> text?
> On Thu, 8 Sep 2016 at 04:43, <Simon.Cox@csiro.au> wrote:
>
>> The recent revision of ISO 19109 added material on Coverages (as well as
>> Observations) that was not in the original, recognising that coverages are
>> important tools for some applications. You might also like to consider
>> these sections from ISO 19109:2013
>>
>>
>>
>> 7.2.2 Coverages
>>
>>
>>
>> Many aspects of the real-world may be represented as features whose
>> properties are single-valued and static. These conventional features
>> provide a model of the world in terms of discrete objects located in it.
>> However, in some applications it is more useful to use a model focussing on
>> the variation of property values in space and time, formalized as
>> coverages. Users of geographic information may utilize both viewpoints.
>> While coverages are themselves strictly features as well, it is common to
>> contrast coverages and non-coverage features when discussing the
>> functionality provided by each viewpoint. In the following discussion the
>> name ‘feature’ refers to non-coverage features.
>>
>> 
>>
>> The feature and coverage representations may be related in several ways:
>>
>>
>>
>> — signal processing to find and characterize features: signals in
>> coverages may provide evidence for the existence, location and type of
>> features, detected through modelling and interpretation;
>>
>>
>>
>> EXAMPLE 1 Patterns of colour or other radiance bands within a
>> remotely-sensed image may be used to infer the existence of specific
>> objects or features on the ground.
>>
>>
>>
>> EXAMPLE 2 Signals in a geophysical borehole log may be used to infer the
>> presence of particular rock-units at underground locations.
>>
>>
>>
>> — coverage-typed feature properties: feature properties whose value vary
>> within the scope of a feature may be described as coverages whose domain
>> extent is the geometry of the feature;
>>
>>
>>
>> EXAMPLE 3 The variation of concentration of a particular ore-mineral
>> within a mine may be described as a spatial function or coverage within the
>> spatial limits of the mine.
>>
>>
>>
>> — features sample a coverage: the values of a common property of a set of
>> features provide a discrete sampling of a coverage, whose range type is the
>> property, and whose domain is the aggregate geometry of the set of features.
>>
>>
>>
>> EXAMPLE 4 The temperature at a set of weather stations may be compiled to
>> show the spatial variation of temperature across the region where the
>> stations are located.
>>
>>
>>
>> A constraint in the latter two cases is that a property-type from a
>> feature catalogue is the range-type of a coverage description in the same
>> universe of discourse.
>>
>>
>>
>> The case of features having property values that vary within the scope of
>> the feature can be described using the general feature model (7.5.8).
>>
>>
>>
>> While the coverage model is described in detail in ISO 19123, an
>> application schema may include both feature- and coverage-types.
>>
>> NOTE The feature and coverage viewpoints are related to (though not
>> identical with) the so-called ‘vector’ and ‘raster’ approaches from
>> traditional GIS implementations.
>>
>>
>>
>> Then, immediately following:
>>
>>
>>
>> 7.2.3 Properties and observations
>>
>>
>>
>> Property values are associated with features and coverages. In the case
>> of features, a property value is associated with a classified object. In
>> the case of coverages, a property value is associated with a position in
>> the domain.
>>
>>
>>
>> Later
>>
>>
>>
>> 8.8 Rules for use of coverage functions
>>
>>
>>
>> Coverage functions are used to describe characteristics of real-world
>> phenomena that vary over space and/or time. Typical examples are
>> temperature, elevation and precipitation. A coverage contains a set of such
>> values, each associated with one of the elements in a spatial, temporal or
>> spatio-temporal domain. Typical spatial domains are point sets (e.g. sensor
>> locations), curve sets (e.g. contour lines), grids (e.g. orthoimages,
>> elevation models), etc. A property whose value varies as a function of time
>> may be represented as a temporal coverage or time-series. A continuous
>> coverage is associated with a method for interpolating values at spatial
>> positions between the elements of a domain, e.g. between two points or
>> contour lines.
>>
>>
>>
>> *From:* Jeremy Tandy [mailto:jeremy.tandy@gmail.com]
>> *Sent:* Thursday, 8 September 2016 7:17 AM
>> *To:* SDW WG Public List <public-sdw-wg@w3.org>
>> *Subject:* updates to the Best Practice document
>>
>>
>>
>> Following today's BP call, I've now added into the BP doc what I was
>> talking about:
>>
>>
>>
>> * A section explaining about Coverages [1] (thanks to Jon Blower; I
>> repurposed one of his Melodies blog posts!)
>>
>> * The beginnings of a section that tries to provide a linear path through
>> the decisions you might make when publishing data: "How to use these best
>> practices" [2] ... this tries to combine SDW and DWBP best practices into a
>> coherent whole ... that said, I've found it really hard to plan this out; I
>> think it's working (& there's more in my head that I unfortunately don't
>> have time to write before I disappear tomorrow ... leaving no more time for
>> update before TPAC.
>>
>>
>>
>> Hope these additions are worthwhile.
>>
>>
>>
>> Jeremy
>>
>>
>>
>> [1]: http://w3c.github.io/sdw/bp/#coverages
>>
>> [2]: http://w3c.github.io/sdw/bp/#how-to-use
>>
>
Received on Thursday, 8 September 2016 09:51:00 UTC

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