Rebuilding all maps error ? why how

[jun1216]

Rebuilding all maps
NOTE: Because your Cacti poller process probably doesn't run as the same user as your webserver, it's possible this will fail with file permission problems even though the normal poller process runs fine. In some situations, it MAY have memory_limit problems, if your mod_php/ISAPI module uses a different php.ini to your command-line PHP.

06/27/2008 08:59:19 AM - WEATHERMAP
: Poller[0] Weathermap 0.95b starting - Normal logging mode. Turn on DEBUG in Cacti for more information
06/27/2008 08:59:19 AM - WEATHERMAP: Poller[0]

No image (gd) extension is loaded. This is required by weathermap. [WMWARN20]
06/27/2008 08:59:19 AM - WEATHERMAP: Poller[0]
run check.php to check PHP requirements.
06/27/2008 08:59:19 AM - WEATHERMAP: Poller[0] Required modules for PHP Weathermap 0.95b were not present. Not running. [WMPOLL08]