[postgis-tickets] [PostGIS] #3061: ST_GeomFromGeoJSON strips coordinates

[PostGIS]

#3061: ST_GeomFromGeoJSON strips coordinates
---------------------------------+------------------------------------------
 Reporter:  slaskis              |       Owner:  pramsey
     Type:  defect               |      Status:  new    
 Priority:  medium               |   Milestone:         
Component:  postgis              |     Version:  2.1.x  
 Keywords:  geojson, linestring  |  
---------------------------------+------------------------------------------
 I'm storing some geo paths in PostGIS using GeoJSON and the
 ST_GeomFromGeoJSON()-function but I just found an issue with it:

 {{{
 SELECT
 ST_NumPoints(ST_GeomFromGeoJSON('{"type":"LineString","coordinates":[[0,0],[1,1],[1,1],[2,2]]}'))
 = 4; -- FALSE

 SELECT ST_NumPoints(ST_GeomFromText('LINESTRING (0 0,1 1,1 1,2 2)')) = 4;
 -- TRUE
 }}}

 It seems to strip the two 'middle' coordinates because they are the same.
 And I can buy that it would do that but it doesn't do it consistently,
 like when I use ST_GeomFromText() with the same list of coordinates. It
 also does not strip the coordinates when using "type": "MultiPoints"
 instead, but it would be the wrong semantics.

 It's a problem for me because I need the points to match a sequence of
 timestamps as well or data will be lost. And the reason I'm using GeoJSON
 is that the app server is written in Javascript so it just seems natural.

 I'm running Postgres 9.4.1 and {{{SELECT PostGIS_Full_Version()}}} gives
 me:

 {{{
 POSTGIS="2.1.5 r13152" GEOS="3.4.2-CAPI-1.8.2 r3921" PROJ="Rel. 4.8.0, 6
 March 2012" GDAL="GDAL 1.11.1, released 2014/09/24" LIBXML="2.9.1"
 LIBJSON="UNKNOWN" RASTER
 }}}

 I currently workaround this issue by changing the type to MultiPoint and
 then converting it to LineString but it seems like a hack to me:

 {{{
 ST_LineFromMultiPoint(ST_GeomFromGeoJSON('{"type":"MultiPoint","coordinates":[[0,0],[1,1],[1,1],[2,2]]}'))
 }}}

 Originally posted to http://gis.stackexchange.com/questions/136629/st-
 geomfromgeojson-strips-coordinates-is-it-a-bug/136966#136966

-- 
Ticket URL: <https://trac.osgeo.org/postgis/ticket/3061>
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.