We've added a new Perl module that calculates the relative pixel location on the "Google World" for the Google Maps API. This module will return a pixel coordinate when passed a latitude, longitude and zoom factor that can be used to correctly locate objects in an image used as a GGroundOverlay object.
This module is based on Ian Dee's excellent work to calculate tile names for custom tile layers. There are some differences, mostly in how the calculation is performed and rounding, but essentially, it is the same calculation found in Google's Javascript API code. An example has been added to demonstrate this routine in action: goverlay.htm
USNaviguide_Google_RelPix.pm - A Perl Module