[postgis-devel] [PostGIS] #1747: Allow calibrating a linestring from a collection of PointM

[PostGIS]

#1747: Allow calibrating a linestring from a collection of PointM
-------------------------+--------------------------------------------------
 Reporter:  amaneiro     |       Owner:  pramsey      
     Type:  enhancement  |      Status:  new          
 Priority:  medium       |   Milestone:  PostGIS 1.5.4
Component:  postgis      |     Version:  1.5.X        
 Keywords:               |  
-------------------------+--------------------------------------------------
 Nowadays, postgis allow calibrating a linestring with ST_AddMeasure.
 Although very useful, it is not enough to cover some common cases when
 calibrating lines: for example, in road management is very usual that the
 ratio between a route's length and its measures is not constant. It's
 typical to have a table with measured points (mileage points, for example)
 and use it to calibrate the linestring.

 So, a method to calibrate a linestring from a collection of PointM would
 be very helpful. Something like ... ?

 {{{
 geometry ST_AddMeasure(geometry geom_mline, geometry points_collection);
 }}}


 To take into account:

 * the measured points not intersect with the line: the user should be able
 to set a offset/buffer for the points to be snapped to linestring.
 Somethink like ... ?

 {{{
 geometry ST_AddMeasure(geometry geom_mline, geometry points_collection,
 float buffer);
 }}}

 * start & end points of linestring: sometimes, the collection of measured
 points provided might not to be the start or end points of the linestring.
 I see two actions could be taken to prevent this: 1) require the user to
 provide a collection where the points match up to the ones on linestring
 or 2) allow the user to set measures for start & end points of linestring.
 Something like... ?

 {{{
 geometry ST_AddMeasure(geometry geom_mline, geometry points_collection,
 float start_measure, float end_measure);
 }}}

 * See [http://postgis.refractions.net/pipermail/postgis-
 users/2012-March/033350.html this thread] for more info.

-- 
Ticket URL: <http://trac.osgeo.org/postgis/ticket/1747>
PostGIS <http://trac.osgeo.org/postgis/>
The PostGIS Trac is used for bug, enhancement & task tracking, a user and developer wiki, and a view into the subversion code repository of PostGIS project.