Henning,
I have done something simelar in R:base, but it would be fairly easy to
convert the code to do it in Tango.
My problem was that I needed to find all of the providers in a given
approximate distance say 30 miles from a client. I did it by using square
approximations from zipcode centers.
I have a table with all 70,000 US zipcodes and the longitude and latitude of
the center of every zipcode.
Now you look up the long & lat for the client to get your starting zipcode.
Approximitaly 1 minute is equal to 1 knotical mile, or 1.15 miles, so I just
compute the corners of the square for the number of miles I want and get
long & lat for the corners. Now it is simple select to get all of the
zipcodes in my square which I then join back to the addresses of my
providers.
I am not sure how you could make this work crossing countries. I am very
ignorant when it comes to processing international address. I would venture
to guess each country must have something equivelent to US zipcode, and you
would need to find the GPS information for those points. Anyway this method
is very simple and very fast.
Troy Sosamon
Denver, Co.
-------- Original Message
Any suggestions on how I can implement a database search which returns rows
for not only the requested State and/or country but also rows for
geographically surrounding and nearby states or countries?
I guess I could create a manually populated table of nearby states or
countries (lets call them regions to be more general) for each region.
Are there any services out there which provide this kind of info? Is there
a site that can offer this raw data initially? If I can get or pull this
from somewhere, it would be preferred over doing things manually.
Thanks much,
Henning Sittler
www.inscriber.com
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