[postgis-tickets] [PostGIS] #4831: Incorrect precision of ST_AsGeoJSON output in PostGIS 2.x and 3.0

[PostGIS]

#4831: Incorrect precision of ST_AsGeoJSON output in PostGIS 2.x and 3.0
---------------------+---------------------------
 Reporter:  Ariki    |      Owner:  pramsey
     Type:  defect   |     Status:  new
 Priority:  medium   |  Milestone:  PostGIS 3.0.4
Component:  postgis  |    Version:  3.0.x
 Keywords:           |
---------------------+---------------------------
 I use PostGIS 3.0.3 on Linux x64, GEOS 3.8.1. Also tried with PostGIS 2.5
 docker image, which is also affected.

 PostGIS 3.1 doesn't have this bug.

 SQL query:

 {{{
 select
         maxdecimaldigits,
         ST_AsGeoJSON(
                 ST_Point(123456789.123456, 123459.123456789),
                 maxdecimaldigits,
                 0
         )
 from generate_series(0, 16) maxdecimaldigits;
 }}}

 Output (CSV):

 {{{
 0       "{""type"":""Point"",""coordinates"":[123456789,123459]}"
 1       "{""type"":""Point"",""coordinates"":[123456789.1,123459.1]}"
 2       "{""type"":""Point"",""coordinates"":[123456789.12,123459.12]}"
 3       "{""type"":""Point"",""coordinates"":[123456789.123,123459.123]}"
 4
 "{""type"":""Point"",""coordinates"":[123456789.1235,123459.1235]}"
 5
 "{""type"":""Point"",""coordinates"":[123456789.12346,123459.12346]}"
 6
 "{""type"":""Point"",""coordinates"":[123456789.123456,123459.123457]}"
 7
 "{""type"":""Point"",""coordinates"":[123456789.123456,123459.1234568]}"
 8
 "{""type"":""Point"",""coordinates"":[123456789.123456,123459.12345679]}"
 9
 "{""type"":""Point"",""coordinates"":[123456789,123459.123456789]}"
 10      "{""type"":""Point"",""coordinates"":[123456789.1,123459.1235]}"
 11      "{""type"":""Point"",""coordinates"":[123456789.12,123459.12346]}"
 12
 "{""type"":""Point"",""coordinates"":[123456789.123,123459.123457]}"
 13
 "{""type"":""Point"",""coordinates"":[123456789.1235,123459.1234568]}"
 14
 "{""type"":""Point"",""coordinates"":[123456789.12346,123459.12345679]}"
 15
 "{""type"":""Point"",""coordinates"":[123456789.123456,123459.123456789]}"
 16
 "{""type"":""Point"",""coordinates"":[123456789.123456,123459.123456789]}"
 }}}

 Notice that in some cases the number of decimal places in the output is
 not what you can expect. In guess, it depends on length of the integer
 part of the number. So when the geometry is in degrees, the bug is harder
 to notice, but it still exists.

-- 
Ticket URL: <https://trac.osgeo.org/postgis/ticket/4831>
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