The Census ZCTA polygon database has been updated only a couple of times. I believe there is a 1990, 2000 and "current" version which is really 2002. In order to "fill in the blanks" as you put it, you'll need some historical zip code data from the USPS, I personally think you're going to have a difficult time finding it. That data is fairly perishable and most companies who use zip code data only care about the most current, not what it was a year ago.
I suppose if you had a list of addresses from the period you're interested in with their existing zip codes, geocoded them without the zip code and then used a convex hull algorithm to convert the data into a polygon you'd have something close, the problem would be figuring out the borders where one zip code lies next to another. If you're only concerned with a couple of zip codes, you could easily do it by hand, using the best spatial tool ever created, your brain. Doing so automatically with a program would be quite a bit more complex. It could be that ESRI has a historical zip code polygon archive, you might contact them to see what they have and what it will cost. -John Coryat http://maps.huge.info http://www.usnaviguide.com --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Google Maps API" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/Google-Maps-API?hl=en -~----------~----~----~----~------~----~------~--~---
