[postgis-tickets] [PostGIS] #4054: Small change in behavior of ST_SimplifyVW

[PostGIS]

#4054: Small change in behavior of ST_SimplifyVW
---------------------+---------------------------
 Reporter:  nicklas  |      Owner:  pramsey
     Type:  defect   |     Status:  new
 Priority:  medium   |  Milestone:  PostGIS 2.5.0
Component:  postgis  |    Version:  trunk
 Keywords:           |
---------------------+---------------------------
 I would like to change the threshold usage in ST_SimplifyVW from

 keeping vertex points that meets


 {{{
 effective_area > threshold
 }}}

 to

 {{{
 effective_area >= threshold
 }}}

 The reason is that for ST_SimplifyVW it will more or less never make a
 difference, but in the more generic function ST_FilterByM like this:

 SELECT FilterByM('LINESTRING(1 1 0 1, 1 2 0 5, 1 1 1 7, 1 1 1
 8)'::geometry, 5);

 Then I think the user expects all the three last points to be included in
 the answer and not only the two last points.

 It is also a good thing if:


 {{{
 ST_SimplifyVW(geom, 5)
 }}}

 is identical to

 {{{
 ST_FilterByM(ST_SetEffectiveArea(geom),5)
 }}}

 So if no objections, I will do this change together with posting
 ST_FilterByM and reference this ticket as a breaking change in NEWS.

-- 
Ticket URL: <https://trac.osgeo.org/postgis/ticket/4054>
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