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Subject: RE: [emergency] RE: Sample email to interestedpartiesWRTgeoenhancements to CAP
China has their own geoid, in the US the legal system is NAD, and so forth. These are fine tuned for each country - geodetically the best fit. These are for the geodesist in each country but typically WGS is used for charting and navigation. In the US the difference between NAD 83 and WGS 84 is so small they are for all intents and purposes interchangeable -i.e. use the national system when you are worried about sub-millimeter accuracy and WGS when navigating down a street. I'm sure Air China doesn't switch coordinate systems when they enter/leave Chinese airspace - as I'm sure United doesn't. About once a year (well maybe not last year) I send this group an old article by Cliff Mugnier, a geodesy professor who writes for ASPRS and Professional Surveyor written because his son was in the service in Afghanistan and he was worried about friendly fire mistakes because of coordinate conversions. This year I'll just send a pertinent paragraph: "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. That explanation given to me, eyeball-to-eyeball, made me realize that although the various sophisticated software applications used and developed by the Department of Defense may have warts and deficiencies; those things geodetic have no affect on the warfighter. As long as our combat troops have only DoD equipment, the possibility of friendly fire casualties is minimized because everything positional in the theater of war matches everything else." My personal feeling is we should leave it as it is. But if there is a great user requirement to have different CRSs then the use of them should be well thought out. The DEFAULT should be what's in CAP now. The use of alternative CRS's should be implemented in a way that users have to read/note and understand the identified alternative. We've had a problem in OGC where people have identified one CRS and used another. Somehow we have to be sure this doesn't happen with CAP. Dave David M. Danko GIS Standards Environmental Systems Research Institute, Inc. 8615 Westwood Center Drive Vienna, VA 22182-2214 USA 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:ABott@so.cccounty.us] Sent: Tuesday, November 27, 2007 11:36 AM To: rlake@galdosinc.com; creed@opengeospatial.org Cc: emergency@lists.oasis-open.org; sandro@oss.com Subject: Re: [emergency] RE: Sample email to interestedpartiesWRTgeoenhancements to CAP Local optimization is almost always suboptimal globally. China is entitled to choose their own local usages, but choices have onsequences. I'm not sure it would be appropriate or wise to impose those consequences on everyone else. - Art -----Original Message----- From: <creed@opengeospatial.org> To: Lake, Ron <rlake@galdosinc.com> Cc: <emergency@lists.oasis-open.org> Cc: <sandro@oss.com> Cc: Botterell, Art <ABott@so.cccounty.us> Sent: 11/27/2007 7:36:56 AM Subject: RE: [emergency] RE: Sample email to interestedpartiesWRTgeoenhancements to CAP As I said in an earlier email, support of the new Chinese datum in gospatial data formats, encodings, or software is a mandate in China. This is a perfect example of what Ron is referring to as a local requirement. The rationale for the Chinese requirement is that th new datum is much more accurate than WGS 84 for the majority of China. Carl > Art: > > Then one says that for such devices there is only one CRS and this is > specified by a particular CRS registry entry. In either case the > specification of the CRS MUST be unambiguous, Just agreeing on say > (lat,lon) will not be enough if the different users select for example > different datums as this will lead to the same (lat,lon) corresponding > to different places on the earth. > > Since at the present time, there are not a great number of truly global > alerts - it could make sense to have the single CRS used in one part of > the world differ from that in another part of the world - I think the > key issue is to eliminate ambiguity in the meaning of coordinates. > > Ron > > -----Original Message----- > From: Art Botterell [mailto:ABott@so.cccounty.us] > Sent: November 26, 2007 5:17 PM > To: Ron Lake; emergency@lists.oasis-open.org; sandro@oss.com > Subject: Re: [emergency] RE: Sample email to > interestedpartiesWRTgeoenhancements to CAP > > Ron, that makes perfect sense for full-blown GIS installation, but what > about cellphones and wristwatches and mass-market alerting devices? > What about systems that receive broadcast, one-way signals? If they > can't access these remote lookup/conversion services, significant errors > could result. > > I'd encourage any of us who weren't around for our earlier CAP > proceedings to at least review the introductory text of the current > spec. I suspect some aspects of the application domain that may not be > obvious, especially for folks who come from an IT background more than a > telecommunications perspective. > > - Art > -----Original Message----- > From: "Ron Lake" <rlake@galdosinc.com> > To: <emergency@lists.oasis-open.org> > To: <sandro@oss.com> > To: Botterell, Art <ABott@so.cccounty.us> > > Sent: 11/26/2007 5:03:20 PM > Subject: RE: [emergency] RE: Sample email to interested > partiesWRTgeoenhancements to CAP > > Hi Art: > > I think this is a good point. Suppose you use GML geometries in CAP > constructs. For example, a GML point is encoded as follows: > > <gml:Point srsName = "urn:x-ogc:def:crs:EPSG:4326"> > <gml:pos>45.7 110.6</gml:pos> > </gml:Point> > > The srsName attribute indicates the CRS in use. This does NOT need to > be resolved in real time, but those wishing to consume or generate this > data may wish to look this up. This can be done using a registry such as > > at http://www.epsg-registry.org and entering the URN string or the EPSG > code. A giving alerting community (the whole world or the US or > whatever) can select the set of CRS definitions that they permit. > > If you do not understand the srsName (there could be a default value > also) then you need to talk to a conversion service or request the data > in an srsName you do understand. > > Cheers > > Ron > > > -----Original Message----- > From: Art Botterell [mailto:ABott@so.cccounty.us] > Sent: November 26, 2007 4:38 PM > To: emergency@lists.oasis-open.org; sandro@oss.com > Subject: Re: [emergency] RE: Sample email to interested > partiesWRTgeoenhancements to CAP > > Let's keep our eye on the ball here. Our goal isn't adoption of CAP for > > its own sake and at any cost. The purpose of CAP is to achieve > interoperability among warning systems globally. > > If we start to sacrifice interoperability in pursuit of nominal > adoptions that can't actually communicate with each other, I'm afraid > we'll be justly criticised for having lost sight of our real mission. > > - Art > > > --------------------------------------------------------------------- > To unsubscribe from this mail list, you must leave the OASIS TC that > generates this mail. You may a link to this group and all your TCs in > OASIS > at: > https://www.oasis-open.org/apps/org/workgroup/portal/my_workgroups.php > > > --------------------------------------------------------------------- > To unsubscribe from this mail list, you must leave the OASIS TC that > generates this mail. You may a link to this group and all your TCs in > OASIS > at: > https://www.oasis-open.org/apps/org/workgroup/portal/my_workgroups.php > > > --------------------------------------------------------------------- To unsubscribe from this mail list, you must leave the OASIS TC that generates this mail. You may a link to this group and all your TCs in OASIS at: https://www.oasis-open.org/apps/org/workgroup/portal/my_workgroups.php --------------------------------------------------------------------- To unsubscribe from this mail list, you must leave the OASIS TC that generates this mail. You may a link to this group and all your TCs in OASIS at: https://www.oasis-open.org/apps/org/workgroup/portal/my_workgroups.php
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