[postgis-users] creating linestrings from points, complexish linestrings

[Rhys Stewart]

here is an excerpt from the table:


 parish | pointnumber | parent |  devicetype
--------+-------------+--------+--------------
 KSAS   |           3 |        | START
 KSAS   |           4 | 3      | INTER
 KSAS   |           5 | 4      | INTER
 KSAS   |           6 | 5      | END
 KSAS   |           7 | 3      | INTER
 KSAS   |           8 | 7      | END
 KSAS   |           9 | 7      | END
 KSAS   |          10 |        | START
 KSAS   |          11 | 10     | INTER
 KSAS   |          12 | 11     | INTER
 KSAS   |          13 | 12     | END
 KSAS   |          14 |        | START
 KSAS   |          15 | 14     | END



On 4/4/07, Martin Davis <mbdavis at refractions.net> wrote:
> First of all, don't you need some kind of ordering attribute on the
> points?  Otherwise how would you determine the order the points occur in
> the linestring?
>
> Rhys Stewart wrote:
> > Hi all,
> >
> > I have the following table:
> >
> > CREATE TABLE tmp.children
> > (
> >  parish character varying(50),
> >  pointnumber numeric(18),
> >  parent character varying(254),
> >  devicetype character varying(50),
> >  coordfix geometry
> > )
> >
> > The table holds a parent-child relationship in columns pointnumber and
> > parent.
> > i.e., if a point has a parent the pointnumber  for that parent is in
> > the parent field.
> > The devicetype can either be Start, Inter or End. The only time a row
> > has no parent is when its devicetype is start. There can be any number
> > of inters.
> >
> > I would like to create one linestring encompassing an entire
> > start-inter-end sequence and am having trouble wrapping my brain
> > around it.
> >
> >
> > Any suggestions?
> >
> >
> > Thanks
> > _______________________________________________
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> > postgis-users at postgis.refractions.net
> > http://postgis.refractions.net/mailman/listinfo/postgis-users
> >
>
> --
> Martin Davis
> Senior Technical Architect
> Refractions Research, Inc.
> (250) 383-3022
>
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