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Subject: Re: [emergency] Re: Circle and Polygon
Well stated. Thanks Art - I stand corrected. I also spoke with another implementor of CAP on the same issue of the CRS and withdraw any suggestions of not having WGS as mandatory. Cheers Carl > Carl - > > If the primary purpose of the circles and polygons in CAP was to > provide data for GIS display I'd have an easier time with your > suggestion. But that's not really the case. > > The primary purpose of the geospatial elements in CAP is to enable > location-aware receivers to identify those messages that are relevant > at their locations or at other locations of interest... or, depending > on network architecture, to enable routing mechanisms to make those > determinations on the end-receivers' behalf. So we're talking about > devices that don't need to, and in many cases can't, support > conversions among multiple reference systems. > > As you point out, the geospatial systems that need transformations > from WGS-84 to other CRSs are generally able to do them themselves, > as well as being able to take advantage of even more detailed GML > data that might be included as a resource. But there's a larger > universe of devices out there, at both the input and output ends and > even in the middle, for which cost, weight, power, traffic volume and > other constraints suggest a simpler approach. > > So... again, speaking as just one of the TC membership... I hesitate > to complicate the CAP format, which has been used successfully even > in Australia, unless we're shown an absolute technical need to do so. > Right now the issue seems to be one of local preferences, and we're > never going to be able to please everyone. > > - Art > > > On Jun 15, 2005, at 6/15/05 11:04 AM, Carl Reed wrote: > >> Art - >> >> Thanks for the quick response. >> >> Just to clarify so that there is no misunderstanding: >> >> 1. I agree that specifying WGS 84 as the default CRS and best >> practice is >> a good thing. There is no disagreement here.2. The current CAP 1.0 >> spec references the EPSG definition of WGS 84. This >> is a good thing.3. The current approach works within the contextual >> framework of those who >> have implemented CAP to date. Fine >> That said, please consider: >> >> 4. I am not asking to change this position. >> 5. I am asking for the ability to specify another CRS. >> 6. This does not add complexity - nor does it break interoperability. >> 7. It actually enhances interoperability as ALL >> communities/nations/jurisdictions are accommodated.8. It does not >> break interoperability because the optional element >> provides the EPSG code for the CRS being used. The majority of >> geospatial >> technology providers know of and use these codes.9. Most systems >> ingesting a WGS 84 based CAP payload will have to >> transform any coordinates contained in the CAP message into some other >> projected system, such as State Plane. This is necessary to >> display/portray the location of an alert in the context of a common >> operational picture. >> I am looking toward future usage and flexibility. >> >> If my position falls short and is unacceptable, I will give up pushing >> this position WRT CRS extensibility for CAP and move to other EM TC >> actions and work. >> >> >> >>> [Oops, our notes passed each other in the mail.] >>> >>> On Jun 15, 2005, at 6/15/05 9:42 AM, Carl Reed wrote: >>> >>>> You still appear to be missing the point. We can leave CAP and EDXL >>>> with >>>> WGS 84 as the default (but not mandatory!) so that all existing >>>> implementations work and the level of "simplicity" being sought is >>>> maintained. We are suggesting optional elements that would allow >>>> folks to >>>> use other than WGS 84 as the only CRS. >>>> >>> >>> OK, my mistake... guess we *aren't* all agreed on the need to fix on >>> a single standard reference system. Personally, I think we do, if >>> only in order to keep things simple for implementers. Otherwise >>> we're going to have only local rather than global interoperability of >>> CAP messages. >>> >>> What we're not getting here is a sense of proportion. Is this a >>> serious and widespread problem or just a few folks' personal >>> theoretical axe? I really can't tell... although I'll note again >>> that none of these complaints seem to come from folks who've actually >>> deployed implementations. >>> >>> - 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
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