Hi--
Welcome to the Apple Discussions.
If your iPad is the WiFi only version, the location is calculated using data provided by Skyhook Wireless:
http://www.skyhookwireless.com/
My experience with the iPod touch, which uses the same data, has been that it's pretty accurate. But it may be because more of the U.S. Has been mapped.
They have a page where you can submit a wireless access point:
http://www.skyhookwireless.com/howitworks/submit_ap.php
That should help them be more accurate.
If your iPad is the 3G version with built-in GPS, then I'm not sure what to say: mine's amazingly accurate, within a few feet outdoors.
charlie