[postgis-tickets] [PostGIS] #3172: ST_AddMeasure refuses to set measure of zero-length line

[PostGIS]

#3172: ST_AddMeasure refuses to set measure of zero-length line
-------------------------+---------------------------
 Reporter:  strk         |      Owner:  pramsey
     Type:  enhancement  |     Status:  new
 Priority:  medium       |  Milestone:  PostGIS 2.2.0
Component:  postgis      |    Version:  2.1.x
 Keywords:               |
-------------------------+---------------------------
 In modeling the trajectory of a non-moving object it is useful to be able
 to create a LINESTRING with 2 vertices that have the same XYZ portion but
 different M. Using ST_AddMeasure on such a topologically invalid input
 results in the M being set to 0 in both first and second (last) vertex:
 {{{
 =# select ST_AsText(ST_AddMeasure('LINESTRING(0 0,0 0)', 1, 2));
          st_astext
 ----------------------------
  LINESTRING M (0 0 0,0 0 0)
 (1 row)

 =# select ST_AsText(ST_AddMeasure('LINESTRING(0 0,1 0)', 1, 2));
          st_astext
 ----------------------------
  LINESTRING M (0 0 1,1 0 2)
 (1 row)
 }}}

 I think it would be nice for the first case to return
 {{{
 LINESTRING M (0 0 1,0 0 2)
 }}}

 I know, it's a very special case, but it seems to be well defined.

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Ticket URL: <https://trac.osgeo.org/postgis/ticket/3172>
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