PostGIS – How to Calculate the Azimuth of a Line of a MultiLineString in PostGIS

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I have two spatially enabled tables in PostgreSQL with a geometry in each:
First table is with POINT type, second is with MULTILINESTRING.

I need to calculate the azimuth of the LINESTRING part of a MULTILINESTRING, which is closest to the POINT.

So the question is: how do I extract the LINESTRING in question, and compute the azimuth?

Best Answer

Am I misunderstanding? Isn't this just:

SELECT
   ST_Asimuth(p.geom, ST_ClosestPoint(l.geom,p.geom)) AS azimuth
FROM line l, point p

If you have more than one item in the line and point tables, the question of what condition you join them on becomes important, but as you described it, it's just one item in each.

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[GIS] How to find nearest line from point using PostGIS

SELECT name,ref,type,ST_Distance(ST_Buffer(r.geom,20),ST_SetSRID(ST_MakePoint(lon, lat),4326)) 
FROM roads r 
ORDER BY 4 ASC 
LIMIT 1;

For point in lon/lat coordinates:

SELECT name,ST_Distance(r.geom,ST_SetSRID(ST_MakePoint(lon, lat),4326)) FROM roads r ORDER BY 2 ASC LIMIT 1;

[GIS] PostGIS: Get closest point between geometry and Multipoint

Take a look at ST_ShortestLine. http://postgis.net/docs/manual-2.1/ST_ShortestLine.html

ST_ClosestPoint is the first point in ST_ShortestLine.

Something like this should work.

SELECT DISTINCT ON (a.id) ST_ShortestLine(a.geom,b.geom) FROM table1 a,table2 b ORDER BY a.id,ST_Distance(a.geom,b.geom);

Best Answer

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[GIS] How to find nearest line from point using PostGIS

[GIS] PostGIS: Get closest point between geometry and Multipoint

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