[postgis-users] New Curve Types in 1.2

Ken Southerland southerland at samsix.com
Tue Dec 12 13:36:26 PST 2006

This is very exciting news for us as we are just about to implement 
curves/arcs in our application.  I was just about to write code that would 
store meta data to translate line strings into arcs/curves.  But now maybe I 
don't have to.

Is there any other documentation specific to the new curve types?  I see brief 
mention of them in the html documentation accompanying the source code.  
Specifically I see the following line ...

COMPOUNDCURVE((0 0, 1 1, 1 0),(1 0, 0 1)

...as an example of a mixed curve/straight line sequence.  First off, I'm 
assuming it is missing a closed parantheses at the end of the string.  In 
other words, I'm assuming it should read ...

COMPOUNDCURVE((0 0, 1 1, 1 0),(1 0, 0 1))

... but then a further question I have is how this is read.  I'm assuming that 
this means there is an arc defined by the 3 points in the first set of 
parantheses and then a short straight line sequence followed by the two 
points defined in the second set.  But how is this determined?  What if I had 
a 3-point LineString definition in the second part?  How does the 
CompoundCurve know that I meant a straight line sequence and not a 
CicularString sequence?

Also, are there java classes yet written to handle these, like the LineString 
class found in the java/jdbc/src/org/postgis/ subdirectory?

Also, is it true that only circular arcs are currently implemented?  What is 
the outlook for more complex curves like a Bezier curve?

Cheers!  I'm very thrilled with this news!



Ken Southerland
Senior Consultant
Sam Six, Inc.


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