[elasticdog]

I prefer using the [United Nations Code for Trade and Transport Locations](http://www.unece.org/cefact/locode/service/location.html) (UN/LOCODE) value based on the address of the host's data center. It covers more specific locations than something like the IATA airport codes, and is still a well defined standard.

[walrus01]

Most ISPs will usually use the icann standard two letter ccTLD for the country where the pop is, which is usually similar to what you linked, but not always.