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Subject: Re: [emergency] RE: Geo-GIS subcommittee call tomorrow.

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 

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 

Precision is always an interesting issue, especially how to express 
precision in terms of a standard. Just ask the IETF community.



----- Original Message ----- 
From: "Jacob Westfall" <jake@jpw.biz>
To: <emergency@lists.oasis-open.org>
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?
> -- 
> jake@jpw.biz
> --
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