PostGIS 3D linestring validity with two different Z coordinates





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Maybe I missed something in the docs, but why is this not a valid LINESTRING Z and is a POINT Z when calling st_makeValid?



select st_isvalid(st_geomfromtext('LINESTRING Z (0 0 0,0 0 10)'));



st_isvalid

---------------

f





select st_astext(st_makevalid(st_geomfromtext('LINESTRING Z (0 0 0,0 0 10)')));

st_astext

---------------

POINT Z (0 0 0)





postgis







share|improve this question























  • This looks like a bug to me. SELECT st_isvalid('LINESTRING Z(0 1 1, 0 0 10)'::geometry); returns true, while SELECT st_isvalid('LINESTRING Z(0 0 1, 0 0 10)'::geometry); returns false.

    – John Powell
    Apr 2 at 9:57











  • Interestingly, if you call something like ST_Expand on the invalid Linestring Z, it works as expected. SELECT ST_Astext(ST_Expand('LINESTRING Z(0 0 0, 0 0 10)'::geometry, 1, 1, 1)); returns POLYGON Z ((-1 -1 -1,-1 1 -1,1 1 11,1 -1 11,-1 -1 -1)). I will have a look at the source code later to see if I can find the bug, but, it looks to me that you can probably ignore the ST_Isvalid error. Also, note that ST_GeomFromText is not necessary to construct a LINESTRING Z.

    – John Powell
    Apr 2 at 10:01






  • 2





    I asked on the Postgis dev IRC channel and ST_IsValid only works in 2D, which explains why 0 0 0, 0 0 10 fails and 0 1 0, 0 0 10 works. sfcgal, on which the 3D extensions are based does have an IsValid function. I have been told to request an ST_3dIsValid function be hooked up to sfcgal and the docs be updated. As I suggested before, you are safe to carry on using LINESTRING Z. I will update this once I have filed the bug/request.

    – John Powell
    Apr 2 at 10:31


















2















Maybe I missed something in the docs, but why is this not a valid LINESTRING Z and is a POINT Z when calling st_makeValid?



select st_isvalid(st_geomfromtext('LINESTRING Z (0 0 0,0 0 10)'));



st_isvalid

---------------

f





select st_astext(st_makevalid(st_geomfromtext('LINESTRING Z (0 0 0,0 0 10)')));

st_astext

---------------

POINT Z (0 0 0)





postgis







share|improve this question























  • This looks like a bug to me. SELECT st_isvalid('LINESTRING Z(0 1 1, 0 0 10)'::geometry); returns true, while SELECT st_isvalid('LINESTRING Z(0 0 1, 0 0 10)'::geometry); returns false.

    – John Powell
    Apr 2 at 9:57











  • Interestingly, if you call something like ST_Expand on the invalid Linestring Z, it works as expected. SELECT ST_Astext(ST_Expand('LINESTRING Z(0 0 0, 0 0 10)'::geometry, 1, 1, 1)); returns POLYGON Z ((-1 -1 -1,-1 1 -1,1 1 11,1 -1 11,-1 -1 -1)). I will have a look at the source code later to see if I can find the bug, but, it looks to me that you can probably ignore the ST_Isvalid error. Also, note that ST_GeomFromText is not necessary to construct a LINESTRING Z.

    – John Powell
    Apr 2 at 10:01






  • 2





    I asked on the Postgis dev IRC channel and ST_IsValid only works in 2D, which explains why 0 0 0, 0 0 10 fails and 0 1 0, 0 0 10 works. sfcgal, on which the 3D extensions are based does have an IsValid function. I have been told to request an ST_3dIsValid function be hooked up to sfcgal and the docs be updated. As I suggested before, you are safe to carry on using LINESTRING Z. I will update this once I have filed the bug/request.

    – John Powell
    Apr 2 at 10:31














2












2








2








Maybe I missed something in the docs, but why is this not a valid LINESTRING Z and is a POINT Z when calling st_makeValid?



select st_isvalid(st_geomfromtext('LINESTRING Z (0 0 0,0 0 10)'));



st_isvalid

---------------

f





select st_astext(st_makevalid(st_geomfromtext('LINESTRING Z (0 0 0,0 0 10)')));

st_astext

---------------

POINT Z (0 0 0)





postgis







share|improve this question














Maybe I missed something in the docs, but why is this not a valid LINESTRING Z and is a POINT Z when calling st_makeValid?



select st_isvalid(st_geomfromtext('LINESTRING Z (0 0 0,0 0 10)'));



st_isvalid

---------------

f





select st_astext(st_makevalid(st_geomfromtext('LINESTRING Z (0 0 0,0 0 10)')));

st_astext

---------------

POINT Z (0 0 0)





postgis




postgis






share|improve this question













share|improve this question











share|improve this question




share|improve this question










asked Apr 2 at 7:52









NovotmikeNovotmike

323




323













  • This looks like a bug to me. SELECT st_isvalid('LINESTRING Z(0 1 1, 0 0 10)'::geometry); returns true, while SELECT st_isvalid('LINESTRING Z(0 0 1, 0 0 10)'::geometry); returns false.

    – John Powell
    Apr 2 at 9:57











  • Interestingly, if you call something like ST_Expand on the invalid Linestring Z, it works as expected. SELECT ST_Astext(ST_Expand('LINESTRING Z(0 0 0, 0 0 10)'::geometry, 1, 1, 1)); returns POLYGON Z ((-1 -1 -1,-1 1 -1,1 1 11,1 -1 11,-1 -1 -1)). I will have a look at the source code later to see if I can find the bug, but, it looks to me that you can probably ignore the ST_Isvalid error. Also, note that ST_GeomFromText is not necessary to construct a LINESTRING Z.

    – John Powell
    Apr 2 at 10:01






  • 2





    I asked on the Postgis dev IRC channel and ST_IsValid only works in 2D, which explains why 0 0 0, 0 0 10 fails and 0 1 0, 0 0 10 works. sfcgal, on which the 3D extensions are based does have an IsValid function. I have been told to request an ST_3dIsValid function be hooked up to sfcgal and the docs be updated. As I suggested before, you are safe to carry on using LINESTRING Z. I will update this once I have filed the bug/request.

    – John Powell
    Apr 2 at 10:31



















  • This looks like a bug to me. SELECT st_isvalid('LINESTRING Z(0 1 1, 0 0 10)'::geometry); returns true, while SELECT st_isvalid('LINESTRING Z(0 0 1, 0 0 10)'::geometry); returns false.

    – John Powell
    Apr 2 at 9:57











  • Interestingly, if you call something like ST_Expand on the invalid Linestring Z, it works as expected. SELECT ST_Astext(ST_Expand('LINESTRING Z(0 0 0, 0 0 10)'::geometry, 1, 1, 1)); returns POLYGON Z ((-1 -1 -1,-1 1 -1,1 1 11,1 -1 11,-1 -1 -1)). I will have a look at the source code later to see if I can find the bug, but, it looks to me that you can probably ignore the ST_Isvalid error. Also, note that ST_GeomFromText is not necessary to construct a LINESTRING Z.

    – John Powell
    Apr 2 at 10:01






  • 2





    I asked on the Postgis dev IRC channel and ST_IsValid only works in 2D, which explains why 0 0 0, 0 0 10 fails and 0 1 0, 0 0 10 works. sfcgal, on which the 3D extensions are based does have an IsValid function. I have been told to request an ST_3dIsValid function be hooked up to sfcgal and the docs be updated. As I suggested before, you are safe to carry on using LINESTRING Z. I will update this once I have filed the bug/request.

    – John Powell
    Apr 2 at 10:31

















This looks like a bug to me. SELECT st_isvalid('LINESTRING Z(0 1 1, 0 0 10)'::geometry); returns true, while SELECT st_isvalid('LINESTRING Z(0 0 1, 0 0 10)'::geometry); returns false.

– John Powell
Apr 2 at 9:57





This looks like a bug to me. SELECT st_isvalid('LINESTRING Z(0 1 1, 0 0 10)'::geometry); returns true, while SELECT st_isvalid('LINESTRING Z(0 0 1, 0 0 10)'::geometry); returns false.

– John Powell
Apr 2 at 9:57













Interestingly, if you call something like ST_Expand on the invalid Linestring Z, it works as expected. SELECT ST_Astext(ST_Expand('LINESTRING Z(0 0 0, 0 0 10)'::geometry, 1, 1, 1)); returns POLYGON Z ((-1 -1 -1,-1 1 -1,1 1 11,1 -1 11,-1 -1 -1)). I will have a look at the source code later to see if I can find the bug, but, it looks to me that you can probably ignore the ST_Isvalid error. Also, note that ST_GeomFromText is not necessary to construct a LINESTRING Z.

– John Powell
Apr 2 at 10:01





Interestingly, if you call something like ST_Expand on the invalid Linestring Z, it works as expected. SELECT ST_Astext(ST_Expand('LINESTRING Z(0 0 0, 0 0 10)'::geometry, 1, 1, 1)); returns POLYGON Z ((-1 -1 -1,-1 1 -1,1 1 11,1 -1 11,-1 -1 -1)). I will have a look at the source code later to see if I can find the bug, but, it looks to me that you can probably ignore the ST_Isvalid error. Also, note that ST_GeomFromText is not necessary to construct a LINESTRING Z.

– John Powell
Apr 2 at 10:01




2




2





I asked on the Postgis dev IRC channel and ST_IsValid only works in 2D, which explains why 0 0 0, 0 0 10 fails and 0 1 0, 0 0 10 works. sfcgal, on which the 3D extensions are based does have an IsValid function. I have been told to request an ST_3dIsValid function be hooked up to sfcgal and the docs be updated. As I suggested before, you are safe to carry on using LINESTRING Z. I will update this once I have filed the bug/request.

– John Powell
Apr 2 at 10:31





I asked on the Postgis dev IRC channel and ST_IsValid only works in 2D, which explains why 0 0 0, 0 0 10 fails and 0 1 0, 0 0 10 works. sfcgal, on which the 3D extensions are based does have an IsValid function. I have been told to request an ST_3dIsValid function be hooked up to sfcgal and the docs be updated. As I suggested before, you are safe to carry on using LINESTRING Z. I will update this once I have filed the bug/request.

– John Powell
Apr 2 at 10:31










1 Answer
1






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oldest

votes


















3














This is expected behaviour as the existing Postgis/GEOS codebase only checks 2D coordinates, ie, it ignores the z coordinate.



If you run, 



SELECT ST_IsValid('LINESTRING Z(0 1 0, 0 0 10)'::geometry);


it returns true, as you now have a valid 2D LINESTRING.



I was advised on the Postgis developers irc channel to file a feature request, to request a ST_3dIsValid function that would hook into the existing sfcgal IsValid function and, also, a request to update the docs for ST_IsValid.



Note, for now, you can ignore ST_IsValid with LINESTRING Z, as the underlying functionality appears to be correct, eg,



SELECT ST_Astext(ST_Expand('LINESTRING Z(0 0 0, 0 0 10)'::geometry, 1, 1, 1));


returns:




POLYGON Z ((-1 -1 -1,-1 1 -1,1 1 11,1 -1 11,-1 -1 -1))







share|improve this answer
























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    1 Answer
    1






    active

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    active

    oldest

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    active

    oldest

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    3














    This is expected behaviour as the existing Postgis/GEOS codebase only checks 2D coordinates, ie, it ignores the z coordinate.



    If you run, 



    SELECT ST_IsValid('LINESTRING Z(0 1 0, 0 0 10)'::geometry);


    it returns true, as you now have a valid 2D LINESTRING.



    I was advised on the Postgis developers irc channel to file a feature request, to request a ST_3dIsValid function that would hook into the existing sfcgal IsValid function and, also, a request to update the docs for ST_IsValid.



    Note, for now, you can ignore ST_IsValid with LINESTRING Z, as the underlying functionality appears to be correct, eg,



    SELECT ST_Astext(ST_Expand('LINESTRING Z(0 0 0, 0 0 10)'::geometry, 1, 1, 1));


    returns:




    POLYGON Z ((-1 -1 -1,-1 1 -1,1 1 11,1 -1 11,-1 -1 -1))







    share|improve this answer




























      3














      This is expected behaviour as the existing Postgis/GEOS codebase only checks 2D coordinates, ie, it ignores the z coordinate.



      If you run, 



      SELECT ST_IsValid('LINESTRING Z(0 1 0, 0 0 10)'::geometry);


      it returns true, as you now have a valid 2D LINESTRING.



      I was advised on the Postgis developers irc channel to file a feature request, to request a ST_3dIsValid function that would hook into the existing sfcgal IsValid function and, also, a request to update the docs for ST_IsValid.



      Note, for now, you can ignore ST_IsValid with LINESTRING Z, as the underlying functionality appears to be correct, eg,



      SELECT ST_Astext(ST_Expand('LINESTRING Z(0 0 0, 0 0 10)'::geometry, 1, 1, 1));


      returns:




      POLYGON Z ((-1 -1 -1,-1 1 -1,1 1 11,1 -1 11,-1 -1 -1))







      share|improve this answer


























        3












        3








        3







        This is expected behaviour as the existing Postgis/GEOS codebase only checks 2D coordinates, ie, it ignores the z coordinate.



        If you run, 



        SELECT ST_IsValid('LINESTRING Z(0 1 0, 0 0 10)'::geometry);


        it returns true, as you now have a valid 2D LINESTRING.



        I was advised on the Postgis developers irc channel to file a feature request, to request a ST_3dIsValid function that would hook into the existing sfcgal IsValid function and, also, a request to update the docs for ST_IsValid.



        Note, for now, you can ignore ST_IsValid with LINESTRING Z, as the underlying functionality appears to be correct, eg,



        SELECT ST_Astext(ST_Expand('LINESTRING Z(0 0 0, 0 0 10)'::geometry, 1, 1, 1));


        returns:




        POLYGON Z ((-1 -1 -1,-1 1 -1,1 1 11,1 -1 11,-1 -1 -1))







        share|improve this answer













        This is expected behaviour as the existing Postgis/GEOS codebase only checks 2D coordinates, ie, it ignores the z coordinate.



        If you run, 



        SELECT ST_IsValid('LINESTRING Z(0 1 0, 0 0 10)'::geometry);


        it returns true, as you now have a valid 2D LINESTRING.



        I was advised on the Postgis developers irc channel to file a feature request, to request a ST_3dIsValid function that would hook into the existing sfcgal IsValid function and, also, a request to update the docs for ST_IsValid.



        Note, for now, you can ignore ST_IsValid with LINESTRING Z, as the underlying functionality appears to be correct, eg,



        SELECT ST_Astext(ST_Expand('LINESTRING Z(0 0 0, 0 0 10)'::geometry, 1, 1, 1));


        returns:




        POLYGON Z ((-1 -1 -1,-1 1 -1,1 1 11,1 -1 11,-1 -1 -1))








        share|improve this answer












        share|improve this answer



        share|improve this answer










        answered Apr 2 at 11:00









        John PowellJohn Powell

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