How to find SRID for random polygon?

Question

I'm testing spatial database performance on a dataset. Spatial objects in this dataset (stored as WKT in a flat text file) are random valid polygons which have vertex coordinates (x,y) where 100,000> x >0 and same for y.

Currently I'm having problem with inserting these data into PostGIS which has a geometry constraint check and I got an error like "violates check constraint "enforce_srid_polygon ".

So, how can I find/create a srid for my dataset ?

BTW: the polygons are valid polygons which are extracted from images by segmenting objects.

Answer 1

You can query it with Find_SRID. So if your table looks something like:

CREATE TABLE ply
(
  id integer NOT NULL,
  geom geometry(Polygon,4326),
  CONSTRAINT ply_pkey PRIMARY KEY (id)
);

then use:

postgis=# SELECT Find_SRID('', 'ply', 'geom');
 find_srid
-----------
      4326
(1 row)

Answer 2

If I am not wrong, I think SRID is same as WKID in ESRI parlance.
You can get a list of WKIDs from the following URLs:
Projected Coordinate Systems WKID List
Geographic Coordinate Systems WKID List

Cheers
Ujjwal

Answer 3

The SRID if the polygon you are inserting has to match the SRID specified for that geometry column. So whatever you used in the srid argument of AddGeometryColumn is what you need for the INSERT.

Note that random vertices aren't necessarily going to give you valid polygons.