The IP City Cluster Plugin (IPCCP) generates a geographical cluster map based on where from people access you website.
Most likely you are not running PHP5, which is required for the GeoIP API to work. You need to upgrade before using IPCCP.
Actually what we are looking for is accuracy. IPCCP is (of course) 100% precise (having no stochastic parts at all). Accuracy is a different matter. The longitude / latitude values are often more of an estimate. But MaxMind promises monthly updates, so keep checking their website and grab the current databases (or use the links above). But to be honest, for this matter I think it's all good enough. It's all about the impression if you ask me.
You can go ahead and buy their commercial Databases which are currently $420 (base price) + $102 (per monthly update) for the set of City and Country database.
I'll add a legend as we go along. For now just this quick remark: you see four numbers at the bottom left. For the picture above they are: * 2881492 IP-entries numbers found * 2879499 IP-entries numbers found minus the Satellite Operators * 45787 unique IP numbers * 5696 unique places * 727 unique clusters drawn
Using the image maps will probably drastically increase the length of the HTML-code (especially if you have some million entries from all over the place). Just look at the source of this page... Some people might wish for the image only and don't care for the additional information. Hence the option.
IPCCP is generating three pictures. The native 2000*1000px
ipccp_out.jpg, the user specified large version
ipccp_out_big.jpg and the user specified small version
ipccp_out_smal.jpg. The scaling of the later two is done by the PHP GD library, which isn't near up to standards if you ask me. Just compare the scaled version with the scaling done by the browser (which on OSX is done by the far superior QT). Hence I recommend leaving the small GD version be and simply use the big version. Given that most people will look at the zoomed version anyway that actually saves the download of two images.
If you have rights to any maps and are willing to donate them for the project, that would be great. I'll add a feature where the user could choose his/her map from a given available set. The same holds if you have the rights to a more detailed database! Donate them and earn eternal gratitude from millions of WordPress Users.