[Geojson] GeoJSON '1.0'?

Allan Doyle afdoyle at MIT.EDU
Thu Mar 13 06:42:54 PDT 2008

On Mar 13, 2008, at 7:53 AM, Christopher Schmidt wrote:

> On Thu, Mar 13, 2008 at 07:43:59AM -0400, Panagiotis (Peter) A.  
> Vretanos wrote:

> This is essentially all stuff we know. The question comes down to this
> statement:
>> So if you use EPSG:4326 and are encoding the coordinates in x,y (or
>> long,lat) ... well, Raj said it best "You can't do that."!
> *Why?* The answer is obviously not the same for GeoJSON as it is for
> WMS: In WMS, there was no explicit statement that said "Ignore the  
> CRS:
> It's always in x, y." If the reason that there is a problem is because
> the spec is poorly written, then that problem is *solved* with  
> GeoJSON.
> Assuming that you override the ordering of the CRS in your spec: why
> can't you use EPSG:4326?

How about this:

Current Draft 5:
  "If a GeoJSON object has a member named "crs", it is assumed to  
represent the coordinate reference system of the included geometry or  

Proposed fix:
  "If a GeoJSON object has a member named "crs", it is assumed to  
represent the SOURCE coordinate reference system of the included  
geometry or geometries. In other words, the coordinates in GeoJSON  
elements ALWAYS follow the order x,y[,z] and ALWAYS are expressed as  
floating point numbers REGARDLESS of the order and representation used  
in the source coordinate system. The "crs" member is STRICTLY a hint  
that expresses the mathematical relationship between the coordinate  
values in the GeoJSON geometries and the real world. " [Capitalization  
can go away, that's just to make it stand out in this email]

Or something like that. In other words, it should be stressed that  
GeoJSON is not saying the geometries are expressed in the normative  
manner prescribed by the CRS but rather they are transformed from that  
CRS. How the transformation is done is up to the user of GeoJSON since  
some people might even use +-DDMMSS style notation since there are  
EPSG codes that require that as well.

By the way, the only trademark at uspto.gov attached to 'epsg' is  
'ePSG' and refers to " Computer hardware and software, for use with  
medical patient monitoring equipment, for receiving, processing,  
transmitting and displaying data"


Allan Doyle
Director of Technology
MIT Museum

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