Re: updates to the Best Practice document

Hello,

About the difference between spatial data as coverage and spatial data as
geometry: Is the difference between a point cloud and a multipoint clear? I
understand that point clouds are regarded as coverages. Multipoints are
geometry. But I notice that points clouds exist where the points have no
other value next, apart from geometry. One could say that in that case the
mapped value is 'location'... I wonder if readers need more guidance on
when point collections should be modelled as multipoint or as coverage.

Regards,
Frans

On 8 September 2016 at 14:00, Jeremy Tandy <jeremy.tandy@gmail.com> wrote:

> Thank you! I reference ISO 19109 from the coverage definition in the
> glossary (although I've not set up the bibliographic ref yet) so it should
> be credited in the bibliography.
>
> Jeremy
>
> On Thu, 8 Sep 2016 at 12:58, <Simon.Cox@csiro.au> wrote:
>
>> You've largely paraphrased and only directly used a couple of sentences,
>> so unlikely to be a problem. If in doubt, give credit - ie add it to the
>> bibliography.
>>
>> ------------------------------
>> *From:* Jeremy Tandy <jeremy.tandy@gmail.com>
>> *Sent:* Thursday, 8 September 2016 9:50:19 AM
>> *To:* Cox, Simon (L&W, Clayton); public-sdw-wg@w3.org
>> *Subject:* Re: updates to the Best Practice document
>>
>> 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
>>>>
>>>