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Subject: RE: [emergency-gis] Groups - Suggested changes for CAP 2.0 - CRS and GML (Best Practices for CRS - for OASIS.doc) uploaded

Let's not forget the Professional Surveyor article I sent out last year by
Cliff Mugnier who was concerned about the US Army (and his son) in
Afghanistan using bad coordinate transformation parameters and friendly
fire. His fears were allayed when he learned from NGA that they always used
WGS 84. An excerpt:
There are warfighters and there is the Department of Defense (DoD) in
general. Warfighters always have positional detail exclusively referenced to
the World Geodetic System 1984 (WGS84). The maps, the imagery, the
coordinates, everything available to a warfighter is referenced to the WGS84
and nothing but. Transformation software is distributed for the Department
of Defense use in research applications, for building simulators, foreign
aid, cartographic analyses, cartometric evaluations, etc. -geodetic
transformation software is not ever intended for the warfighter.

Perhaps the next version of CAP should have more explanation of why we're
using WGS 84.


David M. Danko
GIS Standards
Environmental Systems Research Institute, Inc.
8620 Westwood Center Drive
Vienna, VA 22182-2214
E-mail: ddanko@esri.com
Tel: 703-506-9515 x 8011
Mobile: 703-989-1863
Fax: 703-506 9514
-----Original Message-----
From: Art Botterell [mailto:acb@incident.com] 
Sent: Monday, January 31, 2005 11:48 PM
To: emergency-gis@lists.oasis-open.org
Subject: Re: [emergency-gis] Groups - Suggested changes for CAP 2.0 - CRS
and GML (Best Practices for CRS - for OASIS.doc) uploaded

Thanks, Carl!

At 8:14 PM -0700 1/31/05, Carl Reed OGC wrote:
>This may all be nit-picky legalize...

Well, maybe a bit.  As you point out, the standards that matter are 
the ones folks use.  As a practitioner I'll confess I'm only 
peripherally concerned with the niceties of CAP's formal status.

Our goal has been... and I'd suggest, in light of the new realities 
of homeland security in the U.S. and globally, should remain... to 
bring workable standards to a sufficient level of stability fast 
enough to let implementers start addressing our target problem-set 
quickly (which in the case of CAP I think we've done)... and then to 
incorporate their learnings iteratively and systematically at a tempo 
that encourages rather than inhibits uptake.

>In the geospatial technology world (remote sensing, sensor webs, 
>location services, GIS, CAD and the list goes on), integration of 
>content from many sources, including alerts, is a paramount 
>requirement of many applications. The concepts of fusion, sharing, 
>and integration requires that proper metadata and content be 

That's undoubtedly true, but (and please forgive my density) I'm 
afraid I'm still not making the leap from that broad statement to the 
specifics of what and why we should change in CAP.  And I'm wondering 
whether this might really be more of an EDXL discussion than a CAP 
issue per se.

>The OGC members are getting ready to start an interoperability 
>experiment in which CAP will be used. They will be evaluating CAP 
>from the perspectives that I just mentioned.

Great... I'm sure several folks in the TC would love to help support 
that!  And might it be easier to cast these proposals in specific 
terms once you have the results of that exercise?

>I am not suggesting that CAP physically support numerous CRS's. I am 
>saying why not have the ability to support any CRS with WGS as a 

Well, as I recall our discussions, the reason the TC originally 
decided to specify WGS-84 was that we didn't want to push the 
complexity of interpreting multiple CRS's onto thousands or even 
millions of potential consuming devices, many of them likely to be 
embedded systems.  And we do provide a mechanism for referencing any 
form of additional data, including geospatial data, as resources to 
the CAP message.  Maybe I'm missing the distinction between "support" 
and "physically support."

>So, let's consider some countries other than the US and what they 
>use for their legal national mapping programs. This is not to say 
>that implementors could not use WGS 84, but there would be pressure 
>to use something else.

Standards do involve choices.  We tried to find the one most widely 
acceptable and seemingly most stable CRS platform for CAP 
applications.  CAP was never intended to be a universal GIS "glue 
language"... for that we have GML, don't we?

>However, by adding a few optional elements, then CAP becomes a much 
>richer messaging protocol that can provide much more content and 
>context if the application developer so desires.

A lot of the value of CAP comes from it being a simple core 
info-structure... so I'm not sure "rich" is automatically a virtue in 
our particular application environment.

	Thirty spokes join together in the hub.
	It is because of what is not there that the cart is useful.
	Clay is formed into a vessel.
	It is because of its emptiness that the vessel is useful.
	Cut doors and windows to make a room.
	It is because of its emptiness that the room is useful.
	Therefore, what is present is used for profit.
	But it is in absence that there is usefulness.

Or as we westerners say, "beware of mission creep."

But again, I see no problem with considering specific proposals to 
achieve specific benefits in line with CAP's defined goals.  Or with 
considering other standards we might be able to develop within EDXL 
to meet GIS-related requirements beyond the particular focus of CAP.

- Art

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