As I explained in my replies on the Waterford OCC site thread, the problem is largely with the Irish ISPs. The ISPs generally don't break down the IP ranges in an easily detected geolocation manner. Google and most of the other major search engines use the RIPE/ARIN delegated IP ranges lists for part of their geolocation but those lists only have country level granularity and generally class C range resolution. To get more accurate data, it is necessary to process the IP whois data. This is a tricky thing to rely upon because some of it is out of date and wrong. There are ranges there that haven't been used for over ten years and are still included. The companies, such as Internet Eireann are gone. However Google may start using domain whois data to optimise things. In addition to tracking every domain in com/net/org/biz/info/ie/mobi/asia and about 2.5M .eu and 3.9M .co.uk, the databases here also have the IP ranges from the major IP registries. This provides more of a god's eye view of the problem that webdevs wouldn't necessarily have.

From what I remember, Google and the other SEs use a variety of sources to establish the location of the end user. Sometimes it works and sometimes it does not. Google and others have some interesting patents on geolocation that work well in theory. However Ireland is still a very fragmented market and it is a comparatively small one. Due to the screwed up IP mapping, even offering adverts by region is iffy. The only reliable one is to offer an Ireland one and use the site keywords and advertiser targeted keywords to narrow it down. It is an imperfect solution. But the reverse problem (mapping non .ie Irish sites on non-Irish IP ranges is even tougher. Google hasn't had much luck with solving that but the solution is really quite simple in cryptographic terms. It is just the dataset is very large.

Regards...jmcc