diff --git a/src/pg/sql/13_PIA.sql b/src/pg/sql/13_PIA.sql
index c395720..e59a3b8 100644
--- a/src/pg/sql/13_PIA.sql
+++ b/src/pg/sql/13_PIA.sql
@@ -40,12 +40,12 @@ BEGIN
 
     -- grid #0
     with c1 as(
-        SELECT CDB_RectangleGrid(polygon, h, h) as c
+        SELECT cdb_crankshaft.CDB_RectangleGrid(polygon, h, h) as c
     )
     SELECT array_agg(c) INTO cells FROM c1;
 
     -- 1st guess: centroid
-    best_d := _Signed_Dist(polygon, ST_Centroid(Polygon));
+    best_d := cdb_crankshaft._Signed_Dist(polygon, ST_Centroid(Polygon));
 
     -- looping the loop
     n := array_length(cells,1);
@@ -75,7 +75,7 @@ BEGIN
 
         -- resample the cell
         with c1 as(
-            SELECT CDB_RectangleGrid(cell, test_h/2, test_h/2) as c
+            SELECT cdb_crankshaft.CDB_RectangleGrid(cell, test_h/2, test_h/2) as c
         )
         SELECT array_agg(c) INTO test_cells FROM c1;
 
@@ -120,3 +120,100 @@ BEGIN
     RETURN dist;
 END;
 $$ language plpgsql IMMUTABLE;
+
+--
+-- Fill given extent with a rectangular coverage
+--
+-- @param ext Extent to fill. Only rectangles with center point falling
+--            inside the extent (or at the lower or leftmost edge) will
+--            be emitted. The returned hexagons will have the same SRID
+--            as this extent.
+--
+-- @param width With of each rectangle
+--
+-- @param height Height of each rectangle
+--
+-- @param origin Optional origin to allow for exact tiling.
+--               If omitted the origin will be 0,0.
+--               The parameter is checked for having the same SRID
+--               as the extent.
+--
+--
+CREATE OR REPLACE FUNCTION CDB_RectangleGrid(ext GEOMETRY, width FLOAT8, height FLOAT8, origin GEOMETRY DEFAULT NULL)
+RETURNS SETOF GEOMETRY
+AS $$
+DECLARE
+  h GEOMETRY; -- rectangle cell
+  hstep FLOAT8; -- horizontal step
+  vstep FLOAT8; -- vertical step
+  hw FLOAT8; -- half width
+  hh FLOAT8; -- half height
+  vstart FLOAT8;
+  hstart FLOAT8;
+  hend FLOAT8;
+  vend FLOAT8;
+  xoff FLOAT8;
+  yoff FLOAT8;
+  xgrd FLOAT8;
+  ygrd FLOAT8;
+  x FLOAT8;
+  y FLOAT8;
+  srid INTEGER;
+BEGIN
+
+  srid := ST_SRID(ext);
+
+  xoff := 0;
+  yoff := 0;
+
+  IF origin IS NOT NULL THEN
+    IF ST_SRID(origin) != srid THEN
+      RAISE EXCEPTION 'SRID mismatch between extent (%) and origin (%)', srid, ST_SRID(origin);
+    END IF;
+    xoff := ST_X(origin);
+    yoff := ST_Y(origin);
+  END IF;
+
+  --RAISE DEBUG 'X offset: %', xoff;
+  --RAISE DEBUG 'Y offset: %', yoff;
+
+  hw := width/2.0;
+  hh := height/2.0;
+
+  xgrd := hw;
+  ygrd := hh;
+  --RAISE DEBUG 'X grid size: %', xgrd;
+  --RAISE DEBUG 'Y grid size: %', ygrd;
+
+  hstep := width;
+  vstep := height;
+
+  -- Tweak horizontal start on hstep grid from origin
+  hstart := xoff + ceil((ST_XMin(ext)-xoff)/hstep)*hstep;
+  --RAISE DEBUG 'hstart: %', hstart;
+
+  -- Tweak vertical start on vstep grid from origin
+  vstart := yoff + ceil((ST_Ymin(ext)-yoff)/vstep)*vstep;
+  --RAISE DEBUG 'vstart: %', vstart;
+
+  hend := ST_XMax(ext);
+  vend := ST_YMax(ext);
+
+  --RAISE DEBUG 'hend: %', hend;
+  --RAISE DEBUG 'vend: %', vend;
+
+  x := hstart;
+  WHILE x < hend LOOP -- over X
+    y := vstart;
+    h := ST_MakeEnvelope(x-hw, y-hh, x+hw, y+hh, srid);
+    WHILE y < vend LOOP -- over Y
+      RETURN NEXT h;
+      h := ST_Translate(h, 0, vstep);
+      y := yoff + round(((y + vstep)-yoff)/ygrd)*ygrd; -- round to grid
+    END LOOP;
+    x := xoff + round(((x + hstep)-xoff)/xgrd)*xgrd; -- round to grid
+  END LOOP;
+
+  RETURN;
+END
+$$ LANGUAGE 'plpgsql' IMMUTABLE;