How accurate is geo-targeting?

Another newbie question

[farmboy]

AdWords offers me the option of showing my ads across the U.S. or just in a geographic area.

My ISP is located about 200 miles away and Google often thinks I am located in that city, 200 miles away, and shows me "local ads" when I visit a site that displays AdSense or when I do a search at Google.

So how accurate is the geographic targeting?

FarmBoy

[resham5]

In India too, I've seen ads which are targeted to Delhi in Mumbai which are very far from each other.
There are spill-overs in regional targeting, though not sure to what extent.

[Rehan]

I don't know what geo-targeting database Google uses, but if you go to MaxMind.com they have a product that matches IP addresses to cities and they list the accuracy for city-matching in various countries. In the US, their database correctly resolves 80% of the IPs to within 25 miles of the actual location. In the UK, the accuracy is only 46%. Other countries are somewhere in between.

I would expect Google's geo-targeting to be roughly as (in)accurate as that.

[skunker]

This is interesting. I never really paid much attention to accuracy. Now I am concerned.

Should I advertise in two major cities if they are not that far apart? My ISP shows me located in Austin, but I'm really located in San Antonio.

What should I do, choose both for geotargeting?

[Tapolyai]

Technically speaking, I think it is impossible to geotarget perfectly a consumer IP if they are on dynamic IP address.

I have noticed that larger ISPs, IP routes often do not respond to various querries - in essence masking their location and path.

This would explain why a nearby large city (the base of, or large POP of the ISP) would show up, instead of the end-point.

[skunker]

Am I better off just advertising for my entire state? Of course, then the bid increases big time....

[gregbo]

Geotargeting is not reliable. Expect discrepancies. Even if you happen to be using a service that touts 80% accuracy, this doesn't mean the actual traffic you get falls strictly within that 80%.

[LucidSW]

I don't trust geo targeting 100% myself.

There was a thread about two months ago about this subject here. Apparently, AOL users all show up as being in Virginia (I think) because AOL servers are located there. In Canada, half of Quebec users show up as being in Ontario because most use Bell as their provider and the servers are in Toronto. The distance between Montreal and Toronto is over 500 km, so that is a problem.