1

I want to find the index from Line String to insert new vertex on it.

I am using ST_Add Point function but it requires specified index for inserting vertex.How to get those index based on given input points from line string.

My Input Line String: "LINE STRING Z (496328.772173402 4622876.01448448 208.4005,496327.883130287 4622814.67050952 208.4005,496494.578714408 4622814.67050952 208.4005,496497.898850613 4622875.89518039 208.4005)"

My Input Point: 'POINT Z(496458.12794668 4622814.67050952 208.4005)'

Expected Output: "LINE STRING Z (496328.772173402 4622876.01448448 208.4005,496327.883130287 4622814.67050952 208.4005,496458.12794668 4622814.67050952 208.4005,496494.578714408 4622814.67050952 208.4005,496497.898850613 4622875.89518039 208.4005)"

I need to insert on 3rd position on given line string. But i am not able to find the exact segment index for inserting new point.

I am using following query with manual index 2.But i need to get index automatically

update public.linetype
set geom=ST_AddPoint(geom,  ST_Make Point(496458.12794668 4622814.67050952 208.4005),2) where id=4
from public.linetype 

public.linetype is my table name and geom is linestring geometry column.

PostGIS Version 2.4.4 and PostgreSQL 10.4

1
  • 1
    if your point is always on the linestring, you can use this solution
    – JGH
    Aug 4 '20 at 11:01
3

Unfortunately there's no easy way to do this in PostGIS currently. See this answer for a possible solution.

UPDATE: You can use ST_Snap to do the point insertion in one step:

SELECT ST_AsText( ST_Snap( 
  'LINESTRING Z (496328.772173402 4622876.01448448 208.4005,496327.883130287 4622814.67050952 208.4005,496494.578714408 4622814.67050952 208.4005,496497.898850613 4622875.89518039 208.4005)',
  'POINT Z(496458.12794668 4622814.67050952 208.4005)',
  0.1
));

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.