<!DOCTYPE html><html><head><meta http-equiv="Content-Type" content="text/html; charset=utf-8" /></head><body><div data-html-editor-font-wrapper="true" style="font-family: arial, sans-serif; font-size: 13px;">Hi<br><br>I have postgis table which includes a series of Linestrings, I am trying to create a single geometry that includes only the outside layer of line strings.<br><br>An example would be if the line strings described digital 8, formed from squares two boxes, I would want something looked like a rectangle, <br><br>I have tried things like <br><br> select st_convexhull( st_union(st_startpoint(the_geom),st_endpoint(the_geom))) from bar_table<br><br>I assumed that I would get a polygon with the middle bar removed, what I got was a collection of linestrings<br><br>Has anybody got any suggestions?<br><br>regards<br><br><br>Dave.</div></body></html>