ST_LineSubstring

Signature

GEOMETRY ST_LineSubstring(Geometry geom, double start, double end)

Description

Extract a section of the input geom, starting and ending at the given fractions. The returned geometry is a (MULTI)LINESTRING.

Where:

geom is a LINESTRING or a MULTILINESTRING
start is the starting fraction (between 0 and 1). e.g start = 0.1 means that the first point will be placed at a distance equivalent to 10% of the total length of the line.
end is the ending fraction (between 0 and 1),
start < end.

Warning

Only LINESTRING or MULTILINESTRING are supported

Examples

With `LINESTRING`

SELECT ST_LineSubstring('LINESTRING(1 1, 5 5)', 0.1, 0.9);
-- Answer: LINESTRING (1.4 1.4, 4.6 4.6)

With `MULTILINESTRING`

SELECT ST_LineSubstring('MULTILINESTRING((1 1, 5 5, 1 7), 
                                         (6 1, 7 4, 6 6))', 0.1, 0.9);
-- Answer: MULTILINESTRING (
--         (1.716227766016838 1.716227766016838, 5 5, 1.9059644256269408 6.54701778718653), 
--         (6.170710678118655 1.5121320343559643, 7 4, 6.24142135623731 5.517157287525381))

Where `start` > `end`

SELECT ST_LineSubstring('LINESTRING(1 1, 5 5)', 0.9, 0.1);

Answer: SQL Error: Start fraction must be smaller than end fraction;

See also