[postgis-users] Postgis linear referencing

[Carl Anderson]

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.