Hi Jacob, Carl, All,
Since we're having a GIS SC meeting today in about 20 minutes, I'll wait
for the discussion, but RE:CAPv1.2, we have to maintain the 1.x
compatibility. Moving forward, we need to expedite getting CAP 2.0
rolling with a full head of steam. There are a number of other efforts,
as Carl notes, where we can help pull the ICT wagon in a good direction.
Cheers,
Rex
Carl Reed wrote:
> Jacob -
>
> Of course China uses GPS and deploys applications in which the WGS 84
> CRS is used. However, as in the US - and most countries for that
> matter - many local, regional, and even national geo-applications use
> other geoids and related CRSs. In the US, I would guess the vast
> majority (all?) local governments use NAD 27/83 as the CRS of choice
> for many layers (cadastral, surveyed street centerlines etc). There is
> an interesting Datum Transformation diagram here
> http://www.fs.fed.us/database/gps/aboutgps/documents/nad83.pdf
>
> As to accuracy of less than one meter, well, for example Australian
> law mandates that cadastral data be good to well less than one meter.
> Would your property lines to be off by a meter? And talk to any oil
> company getting ready to drill a new well. Given the exacting
> requirements of directional drilling and the distances drilled,
> measuring the location (x,y and z) of the drill head to the most
> exacting accuracy possible is more than just important.
>
> Precision is always an interesting issue, especially how to express
> precision in terms of a standard. Just ask the IETF community.
>
> Regards
>
> Carl
>
> ----- Original Message ----- From: "Jacob Westfall" <>
> To: <>
> Sent: Thursday, September 10, 2009 12:41 PM
> Subject: Re: [emergency] RE: Geo-GIS subcommittee call tomorrow.
>
>
>>> Also, there is the way outstanding issue regarding allowing
>>> alternative coordinate reference systems. For example, the OGC is
>>> working with the Chinese standards community to have a number of OGC
>>> standards translated into Chinese. They require that all CRS
>>> examples be in Xian80 and not WGS84. This is because Xian80 is the
>>> China legal CRS and must be supported in any China standard dealing
>>> with geo.
>>>
>>
>> Regarding the CRS issue, a first question would be whether there is a
>> need to support accuracy of less than 1 meter? Has precision
>> surfaced as a problem for any users? For the chinese example, what
>> is the actually legal requirement? How do they support
>> interoperability with other countries for things like shipping and
>> air traffic data? Don't they have to support WGS84 for civil
>> aviation and satellite navigation?
>>
>> --
>>
>> --
>>
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>
>
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--
Rex Brooks
President, CEO
Starbourne Communications Design
GeoAddress: 1361-A Addison
Berkeley, CA 94702
Tel: 510-898-0670
