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The EWKB that JTS and GEOS implement is based on the PostGIS EWKB
specification (which predates the SQL/MM spec, I think.)<br>
<br>
I don't have a good reference for the PostGIS spec - it would be
nice if there was one online somewhere (hint, hint).<br>
<br>
It might be nice if JTS/GEOS supported the SQL/MM spec as well. Do
you have a reference available for the spec?<br>
<br>
Martin<br>
<br>
On 8/3/2011 4:19 AM, Oyvind Idland wrote:
<blockquote
cite="mid:CAEVk4t3ai3G0ymyRkThY10SixVcukncpb+abY0xu8k1ju9F6CA@mail.gmail.com"
type="cite">Hello,<br>
<br>
i am trying to read WKB chunks based on the iso SQL/MM part3 spec.
However, this doesn't seem to work.<br>
<br>
From the WkbReader source code doc: <br>
"This implementation supports the extended WKB standard for
representing 3-dimensional coordinates. The presence of 3D
coordinates is signified by setting the high bit of the wkbType
word."<br>
<br>
Which extended WKB standard is being refered to here ?<br>
<br>
<br>
<br>
For example, In the SQL/MM spec, various point types are defined
as the following unsigned values (not hex):<br>
<br>
<wkbpoint> 1<br>
<wkbpointz> 3000001<br>
<wkbpointzm> 2000001<br>
<wkbpointm> 4000001<br>
<br>
However, in the WkbReader.cpp the following logic is used:<br>
<br>
int typeInt = dis.readInt();<br>
int geometryType = typeInt & 0xff;<br>
......<br>
bool hasZ = ((typeInt & 0x80000000) != 0);<br>
if (hasZ) inputDimension = 3;<br>
else inputDimension = 2; // doesn't handle M currently<br>
<br>
<br>
<br>
<br>
Is there any plans to implement support for SQL/MM ? (I can
volunteer for a patch, if desired)<br>
<br>
<br>
-- Oyvind<br>
<br>
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