From 75c7ae98e4ff2f7d573fa8ae651e95ab1129484c Mon Sep 17 00:00:00 2001
From: Javier Goizueta <jgoizueta@gmail.com>
Date: Mon, 25 Apr 2016 14:02:26 +0200
Subject: [PATCH] Compute webmercator resolution with full accuracy

Fixes #241
---
 scripts-available/CDB_XYZ.sql | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/scripts-available/CDB_XYZ.sql b/scripts-available/CDB_XYZ.sql
index 58b1998..23c292f 100644
--- a/scripts-available/CDB_XYZ.sql
+++ b/scripts-available/CDB_XYZ.sql
@@ -6,7 +6,7 @@ CREATE OR REPLACE FUNCTION CDB_XYZ_Resolution(z INTEGER)
 RETURNS FLOAT8
 AS $$
   -- circumference divided by 256 is z0 resolution, then divide by 2^z
-  SELECT 40075017.0 / 256 / power(2, z);
+  SELECT 6378137.0*2.0*pi() / 256.0 / power(2.0, z);
 $$ LANGUAGE SQL IMMUTABLE STRICT;
 -- }