To get truly accurate results, you need to specify the Data Center (DC) for the area in question by IP Address or use a fully qualified URL (DC Name); or, use one of the available online services that will feed your query to selected DCs. One such tool is at
Google Data Center Multiple IP Address SEO Research Tool .
Royal Pingdom » Map of all Google data center locations shows a global map of Google's DCs.
Wayfaring Map - Google Datacenters has an interactive map that identifies each DC location.
To get a the name of a particular DC given an IP Address, you can use ping or traceroute. Examples of fully qualified URLs (DC Names) in the US are:
py-in-f104.google.com
rn-in-f104.google.com
nf-in-f104.google.com
wr-in-f104.google.com
jc-in-f104.google.com
hk-in-f104.google.com
lm-in-f104.google.com
kr-in-f104.google.com
kc-in-f99.google.com
kc-in-f104.google.com
qb-in-f104.google.com
eh-in-f104.google.com