# Find the area of points in PostGIS?

I have points that form a line. I would like to assign a radius to each point to give them volume, e.g. 50m and then find the area of the combined points. Does anyone know of a way to do this in PostGIS?

• You mean without counting the area that overlaps multiple times? Apr 8, 2015 at 13:09
• Please edit the extra info you provided in the comments. Apr 10, 2015 at 5:24

I guess you mean the area of the combined 50m buffers?

If so, then like this:

``````SELECT SUM(ST_Area(ST_Buffer(geom, 50))) FROM points;
``````

This assumes that the points are projected in a CRS with meters as units. And I'm not sure I understand what you mean by "points that form a line". Is the PostGIS table a point feature or line feature?

• The points are coordinates from a person walking across a field. So they are points but represent the path that the person walked. Apr 7, 2015 at 19:39
• Then the above should work, provided the coordinate reference system uses a meter units, NOT longitude/latitude Apr 7, 2015 at 19:41
• The area of buffer of every point will be the same so there's no need to call those functions for every point. Apr 8, 2015 at 13:08
• Unless some points are closer than 50 meters and the circles overlap... Apr 8, 2015 at 15:28
• @Micha In which case the result will be the same as the query doesn't aggregate the buffers. Apr 9, 2015 at 16:54

If the area of the buffers should be combined (as not to count the same area several times) then this query should be used:

``````SELECT ST_Area(ST_Union(ST_Buffer(geom, 50))) FROM points;
``````