On Thu, Aug 6, 2009 at 10:27 PM, Jim Brunette<ca...@brownhare.com> wrote: > Is there a lat/lon database that contains the timezone boundaries? > > With a lat/long TZ DB, users could input their city or zip (or heck, if > they know it, their lat/lon), then the app would associate the user's > lat/lon with the TZ lat/lon and output the TZ (if the user's lat/lon was > not found, the app would just fall back to the continent/city names). > > To take it one step further, mobile apps with GPS have real-time > lat/lon, so getting the TZ should be easy... How useful such an mobile > app would be is another question. > > Jim > Hey Jim,
I have seen a suite of mobile apps using GPS data. In fact, one of the earliest commercial apps I developed involved using GPS to produce mapping info for farms (do a search on precision agriculture to get a sense of the kind of app that was - but it is certain it is no longer on the market as it was designed to crawl on DOS ;-) Find a task where time of day is as important as location, and you have the potential for such a mobile app. Theoretically, you're right, as long as there is a lat/lon DB containing TZ boundaries. But in practical terms, it is another question. Determining whether or not a given point is within the bounds of a given polygon in 2D is not trivial. It can be done, and there are well established algorithms to support it, but it carries a cost; and you can multiply that cost by the average number of polygons you have to check before you get the right one. Is there enough hardware supporting the app for the peak number of users? And the list of complications and constraints goes on. Cheers, Ted
