[galeon] Fwd: CDM feature and point types docs
Ron Lake
rlake at galdosinc.com
Fri Mar 14 10:25:17 MDT 2008
Hi Gerry et al:
I think part of the problem is a misunderstanding of the OGC as taking
geospatial concepts and applying them elsewhere. Nothing could be
further from the truth. OGC has been much more about deriving and
applying appropriate abstractions that are intended to be common to many
domains. It began by looking at traditional geographic information as
in mapping but quickly was extended to other "real" domains, because
there is really no such thing as a geospatial domain. The whole
approach to observations for example has its roots in measurement theory
from people like Luce and Fowler who had nothing to do with anything
geospatial.
The notion of feature (read application object) is key point in all of
this. In the early days of computing, the word data referred to the
available abstractions - the numeric or text etc values that could be
stored and moved about. What these values really meant was not captured
in the computing system. This was true in all areas of
science/engineering (I spent more than a decade in research automation
for wind tunnels), mapping, surveying, computer aided drawing/design,
etc etc.
As people began to share information between machines it was of course
initially very bottom up since that was the available representation and
the machine resources could not cope with anything else.
In the early 80's it began to become clear that a deeper representation
of things was needed - not only to share information across domains but
even to make it more generally possible to share information between
programmers/users in one domain or even in one enterprise. This rise of
the object oriented viewpoint, changed the meaning of the word "data"
from simple primitive types to objects - things that model as closely as
possible what we are doing and talking about. This modeling approach
had of course actually started earlier in the world of databases, but
until the 1980's the idea of transporting these models about was not in
the cards.
Today we see the world in terms of objects, entities or features - and
much of the OGC is concerned with what are the appropriate such things
for a given domain or class of domains. This is not a geospatial
viewpoint. It is more that of knowledge engineering.
It is worth noting that the world of building/structure design (computer
aided design) has been going through a similar transformation to the one
being discussed. CAD started as noted above with a focus on geometric
primitives - points, lines etc. Soon, however, it became clear that to
exchange this information with others in a design team - one needed to
know what these things meant - that this line was the edge of a door,
that the door was made of wood etc. Gradually (and I would say the
transformation is not at all complete) this meant switching the
representation so that we start with meaningful entities in the domain
(like door, wall etc) and then describe these things in terms of
geometric and other characteristics. This is the point of the Building
Information Model (BIM) which has been making a lot of noise these days
and is of course leading to the possibility of CAD/GIS integration in a
meaningful way.
I think this same thinking is behind the modeling of observations and
was the origin of my comment that triggered this discussion.
In very crude terms it is something like:
<Point>
<temperature>30</temperature>
<coordinates>50,20</coordinates>
</Point>
vs
<Observation>
<location>
<Point>
<coordinates>50,20</coordinates>
</Point>
</location>
<result>
<temperature>30</temperature>
</result>
</Observation>
Cheers
Ron
-----Original Message-----
From: galeon-bounces at unidata.ucar.edu
[mailto:galeon-bounces at unidata.ucar.edu] On Behalf Of Luis Bermudez
Sent: March 14, 2008 3:10 AM
To: <Simon.Cox at csiro.au>
Cc: galeon at unidata.ucar.edu
Subject: Re: [galeon] Fwd: CDM feature and point types docs
Hi Simon,
So my sense is that we need best practice documents regarding how
interpret in different ways an observation, and how the realization of
these observations could allow communities to interoperate. I don't
think what you said is very clear from the public specification. But
it is getting clear everyday :)
One more comment:
Isn't the sampling strategy part of the observing procedure ?
- Luis
___
Luis Bermudez Ph.D.
Coastal Research Technical Manager
Southeastern Universities Research Association (SURA)
bermudez at sura.org - Office: (202) 408-8211 Mobile: (267) 481-4939
1201 New York Ave. NW Suite 430, Washington DC 20005
On Mar 13, 2008, at 10:25 PM, <Simon.Cox at csiro.au>
<Simon.Cox at csiro.au> wrote:
> Actually they are referring to the characteristics of the sampling
> strategy.
> This can be described in the context of the procedure/platform/sensor,
> or in the context of the foi, or simply reflected by the coverage-
> domain
> within a result expressed as a coverage. They are none of them
> wrong. My
> sense is that common practice in the fluid-earth sciences is the
> latter
> - mostly what is being shifted around is a
> result-with-sampling-strategy-embedded-within (i.e. the grid
> parameters). That's OK. IMHO the O&M model allows us to understand
> this
> better as it provides a language to describe it.
>
> ______
> Simon.Cox at csiro.au CSIRO Exploration & Mining
> 26 Dick Perry Avenue, Kensington WA 6151
> PO Box 1130, Bentley WA 6102 AUSTRALIA
> T: +61 (0)8 6436 8639 Cell: +61 (0) 403 302 672
> Polycom PVX: 130.116.146.28
> <http://www.csiro.au>
>
> ABN: 41 687 119 230
>
> -----Original Message-----
> From: Dr Luis Bermudez
> Sent: Friday, 14 March 2008 11:15 AM
> To: Cox, Simon (E&M, Kensington)
> Cc: gerry.creager at tamu.edu; galeon at unidata.ucar.edu
> Subject: Re: [galeon] Fwd: CDM feature and point types docs
>
> Hi Simon, excellent.
>
> I've been feeling and expressing this same idea. Feature of Interest
> should be an earth realm or a name place from a gazetteer, where we
> could infer the earth realm. Should not be a geometry, as Ron said.
>
> But, my feeling is that when a domain scientists refer to a type of
> data ( trajectory, station, profile .. ) they are really referring to
> characteristics of the observing procedure ( in this case .. the
> constraint behavior of a sensor or platform ) which is confused
> sometimes with the feature of interest.
>
>
> -Luis
>
>
> On Mar 13, 2008, at 9:53 PM, <Simon.Cox at csiro.au> <Simon.Cox at csiro.au>
> wrote:
>
>> Actually I think the issue is that the domain scientists, quite
>> reasonably, are used to working with some domain-assumptions. For
>> example, when you are an atmospheric scientist talking to other
>> atmospheric scientists, the subject of your studies and observations
>> is
>> the atmosphere. Doesn't need to be stated explicitly, or maybe is
>> just
>> inferred from the fact that elevation component of the location is
>> >0.
>>
>> I'm comfortable with this. That's really why the SamplingFeature is
>> useful. It allows you to work with a feature that is primarily
>> defined
>> by its shape for everyday purposes, without totally abandoning a
>> rigorous model that recognises the fact that there is a domain
>> feature
>> underneath, and it is really the domain feature that has the
>> properties.
>>
>>
>> To help with this, here's some "convenience" features, that you can
>> use
>> as the "feature of interest" of an observation, of the "sampled
>> feature"
>> of a sampling-feature ;-)
>>
>>
>
<https://www.seegrid.csiro.au/twiki/bin/view/CGIModel/CGIFeatureRegister
>> #Register_content>
>>
>>
>> ______
>> Simon.Cox at csiro.au CSIRO Exploration & Mining
>> 26 Dick Perry Avenue, Kensington WA 6151
>> PO Box 1130, Bentley WA 6102 AUSTRALIA
>> T: +61 (0)8 6436 8639 Cell: +61 (0) 403 302 672
>> Polycom PVX: 130.116.146.28
>> <http://www.csiro.au>
>>
>> ABN: 41 687 119 230
>>
>> -----Original Message-----
>> From: Gerry Creager [mailto:gerry.creager at tamu.edu]
>> Sent: Friday, 14 March 2008 10:40 AM
>> To: Cox, Simon (E&M, Kensington)
>> Cc: galeon at unidata.ucar.edu
>> Subject: Re: [galeon] Fwd: CDM feature and point types docs
>>
>> I'll revisit O&M Part 2, and admit now that I gave it, at best, a
>> cursory review last time. However, I continue to suggest that part
>> of
>> the problem is that the domain scientists don't all speak
>> "geospatial"
>> as well as they could, and make inference based less on strict
>> definitions than preference and bias. The result is that the
>> potential
>> for interoperability is reduced until we can resolve the semantic
>> issues, and these will likely not be readily resolved with an RDF
>> document or two because of mis-communication.
>>
>> gerry
>>
>> Simon.Cox at csiro.au wrote:
>>> In fact what is measured is the property of the *stuff at the
>>> point* -
>>> i.e. this is a sampling issue. The stuff is the atmosphere, its
>> property
>>> is its thermodynamic potential, and it is sampled at the point. This
>> is
>>> what O&M Part 2 Sampling Features is about, and is why every
>>> sampling
>>> feature (of which SamplingPoint is a special case) has a
>>> "sampledFeature" such as "the atmosphere".
>>>
>>> So, I suggest a good look at O&M Part 2 is in order. I know that
>> Andrew
>>> W has already done this, since he was on the RWG and is credited as
>> one
>>> of the contributors since he provided a lot of feedback.
>>>
>>> Simon
>>>
>>> ______
>>> Simon.Cox at csiro.au CSIRO Exploration & Mining
>>> 26 Dick Perry Avenue, Kensington WA 6151
>>> PO Box 1130, Bentley WA 6102 AUSTRALIA
>>> T: +61 (0)8 6436 8639 Cell: +61 (0) 403 302 672
>>> Polycom PVX: 130.116.146.28
>>> <http://www.csiro.au>
>>>
>>> ABN: 41 687 119 230
>>>
>>> -----Original Message-----
>>> From: galeon-bounces at unidata.ucar.edu
>>> [mailto:galeon-bounces at unidata.ucar.edu] On Behalf Of Gerry Creager
>>> Sent: Friday, 14 March 2008 2:03 AM
>>> To: Unidata GALEON
>>> Subject: Re: [galeon] Fwd: CDM feature and point types docs
>>>
>>> Ron, et al,
>>>
>>> Ah, but then it becomes a science-discipline semantics issue, too.
>>>
>>> I do think in terms of making "point" observations of in-situ
>>> weather
>>> data. The observation is made at a fixed location, at a particular
>>> finite time, and its geometric property is not a bounded region or
>>> polygon, but a point. Realizing there are gaps in this (wind is
>>> measured at 10m above ground, temperature, humidity, pressure at 2
>>> meters, precipitation at 1 meter, direct and diffuse solar radiation
>> at
>>> nominally 2m but may vary, etc) the data are represented to end-
>>> users
>> as
>>>
>>> being at a single spatial point. Think of it as semantic collision
>>> rather than assimilation.
>>>
>>> And, while I don't think I'm completely clueless, I've spoken at the
>>> TCs, and mentioned to you in the past, about "point features" in my
>> use
>>> of WFS to represent observations, without discussion.
>>>
>>> gerry
>>>
>>> Ron Lake wrote:
>>>> Hi all:
>>>>
>>>>
>>>>
>>>> Just a quick comment. I think the idea of a "point feature" is
>>>> misguided. The items covered in the list of point feature types is
>>>> better covered as an observation feature or observation event. The
>>>> observation or observation collection then has geometric
>>> characteristics
>>>> such as where the observer was located, or where the observations
>>>> are
>>
>>>> located. I am generally opposed to the idea of defining features
>>>> by
>>>> their geometry properties since this has the semantics backwards.
>>>> No
>>
>>>> instrument can make "point measurements" - so the items are
>>> observations
>>>> first and these observations then have geometric properties (like
>>>> location or estimated location).
>>>>
>>>>
>>>>
>>>> Cheers
>>>>
>>>>
>>>> Ron
>>>>
>>>>
>>>>
>>>> *From:* galeon-bounces at unidata.ucar.edu
>>>> [mailto:galeon-bounces at unidata.ucar.edu] *On Behalf Of *Ben
>>>> Domenico
>>>> *Sent:* March 13, 2008 9:15 AM
>>>> *To:* Unidata GALEON
>>>> *Subject:* [galeon] Fwd: CDM feature and point types docs
>>>>
>>>>
>>>>
>>>> Hi all,
>>>>
>>>> Please note the DRAFT documents John Caron has created on CDM
>>>> data/feature types. These are in the early stages of discussion
>>>> and
>>>> revision so please keep in mind that this is all very much SUBJECT
>>>> TO
>>
>>>> CHANGE. But the topics covered are important to GALEON so we need
>> to
>>>
>>>> give them some thought.
>>>>
>>>> -- Ben
>>>>
>>>> ---------- Forwarded message ----------
>>>> From: *John Caron* <caron at unidata.ucar.edu
>>> <mailto:caron at unidata.ucar.edu>>
>>>> Date: Mon, Mar 10, 2008 at 1:19 PM
>>>> Subject: CDM feature and point types docs
>>>> To: techies <techies at unidata.ucar.edu
>>> <mailto:techies at unidata.ucar.edu>>
>>>>
>>>> new draft CDM Feature Types:
>>>>
>>>> http://www.unidata.ucar.edu/software/netcdf-java/CDM/
>>>> CDMfeatures.doc
>>>>
>>>> new doc CDM Point Feature Types:
>>>>
>>>> http://www.unidata.ucar.edu/software/netcdf-java/CDM/CDMpoints.doc
>>>>
>>>> feedback appreciated
>>>>
>>>>
>>>>
>>>>
>>>>
>>>
>>
>
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>>>> galeon at unidata.ucar.edu
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>>>
>>
>> --
>> Gerry Creager -- gerry.creager at tamu.edu
>> Texas Mesonet -- AATLT, Texas A&M University
>> Cell: 979.229.5301 Office: 979.458.4020 FAX: 979.862.3983
>> Office: 1700 Research Parkway Ste 160, TAMU, College Station, TX
>> 77843
>>
>> _______________________________________________
>> galeon mailing list
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>> For list information, to unsubscribe, visit:
> http://www.unidata.ucar.edu/mailing_lists/
>
>
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