How to make polygon from buffered point collection in postgis

Question

I'm trying to make polygon of an airport which must be given distance from start point and end point of runway given as latitude and longitude.

Query I've made looks like this:

INSERT INTO airport (name, polygon) 
VALUES(
      'some airport name', 
      ST_SetSRID(
        ST_Collect(
            ST_Buffer(ST_MakePoint(160.04518, -9.43196), 100), 
            ST_Buffer(ST_MakePoint(160.06376, -9.42452), 100)
        ), 4326
      )
);

unfortunately result polygon is very weird, it covers almost all earth. I've also tried to add srid to each point but it also didn't work. Any ideas?

score 0 · Answer 1 · answered Apr 11 '19 at 15:15

0

Thanks to https://stackoverflow.com/a/13872887/4270929 before adding buffer to point it must be cast to geography (in geometry is in different unit I guess?)

ST_Buffer(ST_MakePoint(160.04518, -9.43196)::geography, 100)::geometry, 
ST_Buffer(ST_MakePoint(160.06376, -9.42452)::geography, 100)::geometry

answered Apr 11 '19 at 15:15

Paweł Sosnowski

173
3
12

2

You specified coordinate system 4326, so the unit was in degrees – JGH Apr 11 '19 at 15:22

How to make polygon from buffered point collection in postgis

1 Answers1