[postgis-users] Postgis linear referencing

[Christoph Spoerri]

Carl,

I don't know much about the internal of geocoding and never really used with 
the exception of mapquest ;), but the system you describe sounds more like a 
geocoding system. Something that PostGIS could use as well and (in my 
opinion) seems harder to implement than a LR system.

Please let me know if I'm wrong here,
Christoph

On Tuesday 09 March 2004 03:28, Carl Anderson wrote:
> On 03/08/2004 09:57:27 PM, Paul Ramsey wrote:
> > Randy Goss wrote:
> >>>  What makes you unhappy about your PostGIS installation?
> >>
> >> Lack of decent integration with ArcGIS.  And, while I'm at it, it
> >> would be nice to have linear referencing capability.
> >
> > The first one I have to lay at ESRI's feet :)
> > But the second one is intriguing -- what database capabilities do you
> > think are necessary to support linear referencing? What we are really
> > missing in the linear referencing side is any kind of design
> > direction. What does "linear referencing support" really mean from a
> > database perspective?
>
> We (Fulton County Georgia) are implementing linear referencing tools
> inside postgis and are willing to co-venture with others
>
> target goals are
>
>    functions that take "well known" LRS text and
>          emit Multilinestrings (line events)
>    functions that take a MultiLinestring and emit "well known" LRS text
>    functions that take two points and emit a set
>          of "well known" LRS text
>    functions that take two points and emit a set
>          of Multilinestrings
>    functions snapping points near a LRS to LRS text
>    functions taking LRS text and emitting a geocoded dot (point events)
>    general geocoding functions
>
> what we don't have (yet)
>    build reference system on arcs
>    generalize reference system
>          (reduce parallel arcs, bump outs, ...) ?? JCS here
>
>
>
> C.
>
> LRS text is (by our usage)
>
> A segment is defined by a start offset and an end offset or
> a point is defined by one LRS offset
>
> a LRS offest is defined in one of  *** ways
>
> on <feature name> from <LRS point> to <LRS point>
>
> LRS point::
>    ( Milepost |
>      crossing feature name  (before | after) <intersection name> |
>      address )
>
>
>
> C.
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-- 
Christoph Spoerri
Associate in Research, Duke University
Durham, NC  27708-0332
Tel. (919) 613-8119; Fax (919) 684-8741