ST_LineInterpolatePoint Returns a point interpolated along a line. Second argument is a float8 between 0 and 1 representing fraction of total length of linestring the point has to be located. geometry ST_LineInterpolatePoint geometry a_linestring float8 a_fraction Returns a point interpolated along a line. First argument must be a LINESTRING. Second argument is a float8 between 0 and 1 representing fraction of total linestring length the point has to be located. See for computing the line location nearest to a Point. Since release 1.1.1 this function also interpolates M and Z values (when present), while prior releases set them to 0.0. Availability: 0.8.2, Z and M supported added in 1.1.1 Changed: 2.1.0. Up to 2.0.x this was called ST_Line_Interpolate_Point. &Z_support; A linestring with the interpolated point at 20% position (0.20) --Return point 20% along 2d line SELECT ST_AsEWKT(ST_LineInterpolatePoint(the_line, 0.20)) FROM (SELECT ST_GeomFromEWKT('LINESTRING(25 50, 100 125, 150 190)') as the_line) As foo; st_asewkt ---------------- POINT(51.5974135047432 76.5974135047432) --Return point mid-way of 3d line SELECT ST_AsEWKT(ST_LineInterpolatePoint(the_line, 0.5)) FROM (SELECT ST_GeomFromEWKT('LINESTRING(1 2 3, 4 5 6, 6 7 8)') as the_line) As foo; st_asewkt -------------------- POINT(3.5 4.5 5.5) --find closest point on a line to a point or other geometry SELECT ST_AsText(ST_LineInterpolatePoint(foo.the_line, ST_LineLocatePoint(foo.the_line, ST_GeomFromText('POINT(4 3)')))) FROM (SELECT ST_GeomFromText('LINESTRING(1 2, 4 5, 6 7)') As the_line) As foo; st_astext ---------------- POINT(3 4) , , , ST_LineLocatePoint Returns a float between 0 and 1 representing the location of the closest point on LineString to the given Point, as a fraction of total 2d line length. float8 ST_LineLocatePoint geometry a_linestring geometry a_point Returns a float between 0 and 1 representing the location of the closest point on LineString to the given Point, as a fraction of total 2d line length. You can use the returned location to extract a Point () or a substring (). This is useful for approximating numbers of addresses Availability: 1.1.0 Changed: 2.1.0. Up to 2.0.x this was called ST_Line_Locate_Point. --Rough approximation of finding the street number of a point along the street --Note the whole foo thing is just to generate dummy data that looks --like house centroids and street --We use ST_DWithin to exclude --houses too far away from the street to be considered on the street SELECT ST_AsText(house_loc) As as_text_house_loc, startstreet_num + CAST( (endstreet_num - startstreet_num) * ST_LineLocatePoint(street_line, house_loc) As integer) As street_num FROM (SELECT ST_GeomFromText('LINESTRING(1 2, 3 4)') As street_line, ST_MakePoint(x*1.01,y*1.03) As house_loc, 10 As startstreet_num, 20 As endstreet_num FROM generate_series(1,3) x CROSS JOIN generate_series(2,4) As y) As foo WHERE ST_DWithin(street_line, house_loc, 0.2); as_text_house_loc | street_num -------------------+------------ POINT(1.01 2.06) | 10 POINT(2.02 3.09) | 15 POINT(3.03 4.12) | 20 --find closest point on a line to a point or other geometry SELECT ST_AsText(ST_LineInterpolatePoint(foo.the_line, ST_LineLocatePoint(foo.the_line, ST_GeomFromText('POINT(4 3)')))) FROM (SELECT ST_GeomFromText('LINESTRING(1 2, 4 5, 6 7)') As the_line) As foo; st_astext ---------------- POINT(3 4) , , , ST_LineSubstring Return a linestring being a substring of the input one starting and ending at the given fractions of total 2d length. Second and third arguments are float8 values between 0 and 1. geometry ST_LineSubstring geometry a_linestring float8 startfraction float8 endfraction Return a linestring being a substring of the input one starting and ending at the given fractions of total 2d length. Second and third arguments are float8 values between 0 and 1. This only works with LINESTRINGs. To use with contiguous MULTILINESTRINGs use in conjunction with . If 'start' and 'end' have the same value this is equivalent to . See for computing the line location nearest to a Point. Since release 1.1.1 this function also interpolates M and Z values (when present), while prior releases set them to unspecified values. Availability: 1.1.0, Z and M supported added in 1.1.1 Changed: 2.1.0. Up to 2.0.x this was called ST_Line_Substring. &Z_support; A linestring seen with 1/3 midrange overlaid (0.333, 0.666) --Return the approximate 1/3 mid-range part of a linestring SELECT ST_AsText(ST_Line_SubString(ST_GeomFromText('LINESTRING(25 50, 100 125, 150 190)'), 0.333, 0.666)); st_astext ------------------------------------------------------------------------------------------------ LINESTRING(69.2846934853974 94.2846934853974,100 125,111.700356260683 140.210463138888) --The below example simulates a while loop in --SQL using PostgreSQL generate_series() to cut all --linestrings in a table to 100 unit segments -- of which no segment is longer than 100 units -- units are measured in the SRID units of measurement -- It also assumes all geometries are LINESTRING or contiguous MULTILINESTRING --and no geometry is longer than 100 units*10000 --for better performance you can reduce the 10000 --to match max number of segments you expect SELECT field1, field2, ST_LineSubstring(the_geom, 100.00*n/length, CASE WHEN 100.00*(n+1) < length THEN 100.00*(n+1)/length ELSE 1 END) As the_geom FROM (SELECT sometable.field1, sometable.field2, ST_LineMerge(sometable.the_geom) AS the_geom, ST_Length(sometable.the_geom) As length FROM sometable ) AS t CROSS JOIN generate_series(0,10000) AS n WHERE n*100.00/length < 1; , , ST_LocateAlong Return a derived geometry collection value with elements that match the specified measure. Polygonal elements are not supported. geometry ST_LocateAlong geometry ageom_with_measure float8 a_measure float8 offset Return a derived geometry collection value with elements that match the specified measure. Polygonal elements are not supported. If an offset is provided, the resultant will be offset to the left or right of the input line by the specified number of units. A positive offset will be to the left, and a negative one to the right. Semantic is specified by: ISO/IEC CD 13249-3:200x(E) - Text for Continuation CD Editing Meeting Availability: 1.1.0 by old name ST_Locate_Along_Measure. Changed: 2.0.0 in prior versions this used to be called ST_Locate_Along_Measure. The old name has been deprecated and will be removed in the future but is still available. Use this function only for geometries with an M component &M_support; SELECT ST_AsText(the_geom) FROM (SELECT ST_LocateAlong( ST_GeomFromText('MULTILINESTRINGM((1 2 3, 3 4 2, 9 4 3), (1 2 3, 5 4 5))'),3) As the_geom) As foo; st_asewkt ----------------------------------------------------------- MULTIPOINT M (1 2 3) --Geometry collections are difficult animals so dump them --to make them more digestable SELECT ST_AsText((ST_Dump(the_geom)).geom) FROM (SELECT ST_LocateAlong( ST_GeomFromText('MULTILINESTRINGM((1 2 3, 3 4 2, 9 4 3), (1 2 3, 5 4 5))'),3) As the_geom) As foo; st_asewkt --------------- POINTM(1 2 3) POINTM(9 4 3) POINTM(1 2 3) , ST_LocateBetween Return a derived geometry collection value with elements that match the specified range of measures inclusively. Polygonal elements are not supported. geometry ST_LocateBetween geometry geomA float8 measure_start float8 measure_end float8 offset Return a derived geometry collection value with elements that match the specified range of measures inclusively. Polygonal elements are not supported. Semantic is specified by: ISO/IEC CD 13249-3:200x(E) - Text for Continuation CD Editing Meeting Availability: 1.1.0 by old name ST_Locate_Between_Measures. Changed: 2.0.0 - in prior versions this used to be called ST_Locate_Between_Measures. The old name has been deprecated and will be removed in the future but is still available for backward compatibility. &M_support; SELECT ST_AsText(the_geom) FROM (SELECT ST_LocateBetween( ST_GeomFromText('MULTILINESTRING M ((1 2 3, 3 4 2, 9 4 3), (1 2 3, 5 4 5))'),1.5, 3) As the_geom) As foo; st_asewkt ------------------------------------------------------------------------ GEOMETRYCOLLECTION M (LINESTRING M (1 2 3,3 4 2,9 4 3),POINT M (1 2 3)) --Geometry collections are difficult animals so dump them --to make them more digestable SELECT ST_AsText((ST_Dump(the_geom)).geom) FROM (SELECT ST_LocateBetween( ST_GeomFromText('MULTILINESTRING M ((1 2 3, 3 4 2, 9 4 3), (1 2 3, 5 4 5))'),1.5, 3) As the_geom) As foo; st_asewkt -------------------------------- LINESTRING M (1 2 3,3 4 2,9 4 3) POINT M (1 2 3) , ST_LocateBetweenElevations Return a derived geometry (collection) value with elements that intersect the specified range of elevations inclusively. Only 3D, 4D LINESTRINGS and MULTILINESTRINGS are supported. geometry ST_LocateBetweenElevations geometry geom_mline float8 elevation_start float8 elevation_end Return a derived geometry (collection) value with elements that intersect the specified range of elevations inclusively. Only 3D, 3DM LINESTRINGS and MULTILINESTRINGS are supported. Availability: 1.4.0 &Z_support; SELECT ST_AsEWKT(ST_LocateBetweenElevations( ST_GeomFromEWKT('LINESTRING(1 2 3, 4 5 6)'),2,4)) As ewelev; ewelev ---------------------------------------------------------------- MULTILINESTRING((1 2 3,2 3 4)) SELECT ST_AsEWKT(ST_LocateBetweenElevations( ST_GeomFromEWKT('LINESTRING(1 2 6, 4 5 -1, 7 8 9)'),6,9)) As ewelev; ewelev ---------------------------------------------------------------- GEOMETRYCOLLECTION(POINT(1 2 6),LINESTRING(6.1 7.1 6,7 8 9)) --Geometry collections are difficult animals so dump them --to make them more digestable SELECT ST_AsEWKT((ST_Dump(the_geom)).geom) FROM (SELECT ST_LocateBetweenElevations( ST_GeomFromEWKT('LINESTRING(1 2 6, 4 5 -1, 7 8 9)'),6,9) As the_geom) As foo; st_asewkt -------------------------------- POINT(1 2 6) LINESTRING(6.1 7.1 6,7 8 9) ST_InterpolatePoint Return the value of the measure dimension of a geometry at the point closed to the provided point. float8 ST_InterpolatePoint geometry line geometry point Return the value of the measure dimension of a geometry at the point closed to the provided point. Availability: 2.0.0 &Z_support; SELECT ST_InterpolatePoint('LINESTRING M (0 0 0, 10 0 20)', 'POINT(5 5)'); st_interpolatepoint --------------------- 10 , , ST_AddMeasure Return a derived geometry with measure elements linearly interpolated between the start and end points. geometry ST_AddMeasure geometry geom_mline float8 measure_start float8 measure_end Return a derived geometry with measure elements linearly interpolated between the start and end points. If the geometry has no measure dimension, one is added. If the geometry has a measure dimension, it is over-written with new values. Only LINESTRINGS and MULTILINESTRINGS are supported. Availability: 1.5.0 &Z_support; SELECT ST_AsText(ST_AddMeasure( ST_GeomFromEWKT('LINESTRING(1 0, 2 0, 4 0)'),1,4)) As ewelev; ewelev -------------------------------- LINESTRINGM(1 0 1,2 0 2,4 0 4) SELECT ST_AsText(ST_AddMeasure( ST_GeomFromEWKT('LINESTRING(1 0 4, 2 0 4, 4 0 4)'),10,40)) As ewelev; ewelev ---------------------------------------- LINESTRING(1 0 4 10,2 0 4 20,4 0 4 40) SELECT ST_AsText(ST_AddMeasure( ST_GeomFromEWKT('LINESTRINGM(1 0 4, 2 0 4, 4 0 4)'),10,40)) As ewelev; ewelev ---------------------------------------- LINESTRINGM(1 0 10,2 0 20,4 0 40) SELECT ST_AsText(ST_AddMeasure( ST_GeomFromEWKT('MULTILINESTRINGM((1 0 4, 2 0 4, 4 0 4),(1 0 4, 2 0 4, 4 0 4))'),10,70)) As ewelev; ewelev ----------------------------------------------------------------- MULTILINESTRINGM((1 0 10,2 0 20,4 0 40),(1 0 40,2 0 50,4 0 70))