Is there a way to calculate length of linestring from one point to another?

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If I have one linestring and coordinates of two points on that linestring, what is the easiest way to calculate not shortest distance from those two points, but distance over the given road (given linestring) in PostGIS?



Example of linestring and points A and B on it



So in the given example given linestrin is whole line and I want to calculate length of red line between points A and B.
Any help with this?




postgis postgresql linestring length points




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    up vote
    2
    down vote

    favorite












    If I have one linestring and coordinates of two points on that linestring, what is the easiest way to calculate not shortest distance from those two points, but distance over the given road (given linestring) in PostGIS?



    Example of linestring and points A and B on it



    So in the given example given linestrin is whole line and I want to calculate length of red line between points A and B.
    Any help with this?




    postgis postgresql linestring length points




    share|improve this question






















      up vote
      2
      down vote

      favorite









      up vote
      2
      down vote

      favorite











      If I have one linestring and coordinates of two points on that linestring, what is the easiest way to calculate not shortest distance from those two points, but distance over the given road (given linestring) in PostGIS?



      Example of linestring and points A and B on it



      So in the given example given linestrin is whole line and I want to calculate length of red line between points A and B.
      Any help with this?




      postgis postgresql linestring length points




      share|improve this question












      If I have one linestring and coordinates of two points on that linestring, what is the easiest way to calculate not shortest distance from those two points, but distance over the given road (given linestring) in PostGIS?



      Example of linestring and points A and B on it



      So in the given example given linestrin is whole line and I want to calculate length of red line between points A and B.
      Any help with this?





      postgis postgresql linestring length points





      share|improve this question











      share|improve this question




      share|improve this question










      asked Aug 14 at 6:39









      Anastasia

      132




      132




















          1 Answer
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          This is one way of doing it



          Find out how big fraction of the line is between the 2 points with ST_LineLocatePoint and multiply that fraction with the whole length.



          SELECT 
          (ST_LineLocatePoint(l,p2)-ST_LineLocatePoint(l,p1) )*st_length(l) dist_along_line, 
          st_distance(p1, p2) direct_distance
           FROM
          (
           SELECT 'linestring(1 1, 1 2, 2 2, 5 0, 10 5)'::geometry l, 
           'point(1 2)'::geometry p1, 'point(5 3)'::geometry p2
          ) a





          share|improve this answer




















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            1 Answer
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            active

            oldest

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            1 Answer
            1






            active

            oldest

            votes









            active

            oldest

            votes






            active

            oldest

            votes








            up vote
            4
            down vote



            accepted










            This is one way of doing it



            Find out how big fraction of the line is between the 2 points with ST_LineLocatePoint and multiply that fraction with the whole length.



            SELECT 
            (ST_LineLocatePoint(l,p2)-ST_LineLocatePoint(l,p1) )*st_length(l) dist_along_line, 
            st_distance(p1, p2) direct_distance
             FROM
            (
             SELECT 'linestring(1 1, 1 2, 2 2, 5 0, 10 5)'::geometry l, 
             'point(1 2)'::geometry p1, 'point(5 3)'::geometry p2
            ) a





            share|improve this answer
























              up vote
              4
              down vote



              accepted










              This is one way of doing it



              Find out how big fraction of the line is between the 2 points with ST_LineLocatePoint and multiply that fraction with the whole length.



              SELECT 
              (ST_LineLocatePoint(l,p2)-ST_LineLocatePoint(l,p1) )*st_length(l) dist_along_line, 
              st_distance(p1, p2) direct_distance
               FROM
              (
               SELECT 'linestring(1 1, 1 2, 2 2, 5 0, 10 5)'::geometry l, 
               'point(1 2)'::geometry p1, 'point(5 3)'::geometry p2
              ) a





              share|improve this answer






















                up vote
                4
                down vote



                accepted







                up vote
                4
                down vote



                accepted






                This is one way of doing it



                Find out how big fraction of the line is between the 2 points with ST_LineLocatePoint and multiply that fraction with the whole length.



                SELECT 
                (ST_LineLocatePoint(l,p2)-ST_LineLocatePoint(l,p1) )*st_length(l) dist_along_line, 
                st_distance(p1, p2) direct_distance
                 FROM
                (
                 SELECT 'linestring(1 1, 1 2, 2 2, 5 0, 10 5)'::geometry l, 
                 'point(1 2)'::geometry p1, 'point(5 3)'::geometry p2
                ) a





                share|improve this answer












                This is one way of doing it



                Find out how big fraction of the line is between the 2 points with ST_LineLocatePoint and multiply that fraction with the whole length.



                SELECT 
                (ST_LineLocatePoint(l,p2)-ST_LineLocatePoint(l,p1) )*st_length(l) dist_along_line, 
                st_distance(p1, p2) direct_distance
                 FROM
                (
                 SELECT 'linestring(1 1, 1 2, 2 2, 5 0, 10 5)'::geometry l, 
                 'point(1 2)'::geometry p1, 'point(5 3)'::geometry p2
                ) a






                share|improve this answer












                share|improve this answer



                share|improve this answer










                answered Aug 14 at 7:02









                Nicklas Avén

                11.3k12539




                11.3k12539



























                     

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