[postgis-tickets] [PostGIS] #4696: ST_LocateAlong returns EMPTY geom for certain terminal measures

[PostGIS]

#4696: ST_LocateAlong returns EMPTY geom for certain terminal measures
----------------------+--------------------------------
  Reporter:  pauldzy  |      Owner:  pramsey
      Type:  defect   |     Status:  closed
  Priority:  medium   |  Milestone:  PostGIS 2.5.5
 Component:  postgis  |    Version:  2.5.x
Resolution:  wontfix  |   Keywords:  ST_LocateAlong LRS
----------------------+--------------------------------
Changes (by robe):

 * status:  new => closed
 * resolution:   => wontfix
 * milestone:   => PostGIS 2.5.5


Comment:

 You have a mistake in your query you are not outputting rinsed but calling
 it rinsed.

 It should be


 {{{
 SELECT
  ST_IsValid(a.rawewkb) AS raw_valid
 ,ST_M(ST_StartPoint(a.rawewkb)) AS raw_startM
 ,ST_M(ST_Endpoint(a.rawewkb)) AS raw_endM
 ,ST_AsEWKT(ST_LocateAlong(a.rawewkb,30.46338)) AS raw_locatealong
 ,ST_IsValid(a.rawewkb) AS rinsed_valid
 ,ST_M(ST_StartPoint(a.rinsed)) AS rinsed_startM
 ,ST_M(ST_Endpoint(a.rinsed)) AS rinsed_endM
 ,ST_AsEWKT(ST_LocateAlong(a.rinsed,30.46338)) AS rinsed_locate
 FROM (
    SELECT
         aa.rawewkb
    ,ST_AsEWKT(aa.rawewkb) AS txted
    ,ST_GeomFromEWKT(ST_AsEWKT(aa.rawewkb)) AS rinsed
    FROM (
       SELECT
 ST_GeomFromEWKB(decode('AQIAAGDOEwAAAwAAAEei4br9RCdBbmmOozvgLEHXnlkSoHY+QBCLlwkIRSdBIlcDZybgLEE6r7FLVO86QBDucKJ2RSdBsmULZJjfLEEAAAAAAAAAAA==','base64'))
 AS rawewkb
    ) aa
 ) a;
 }}}

 When I run these I get


 {{{
 Original: true, 30.463379999999997, 0, SRID=5070;MULTIPOINTM EMPTY
 Rinsed: true, 30.46338, 0, SRID=5070;MULTIPOINTM(762494.8650027
 946205.819445891 30.46338)
 }}}

 The ST_AsText is causing your geometry to be rounded, so it's not the same
 geometry as you had to start with.  Sadly this is just the reality of not
 having a tolerance in our system.  That might come in the future.

 So I'm going to mark this as a won't fix.

-- 
Ticket URL: <https://trac.osgeo.org/postgis/ticket/4696#comment:1>
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