Thanks Jonathan. It seems to work pretty well. Larry ----- Original Message ----- From: "Jonathan Stott" <jonathan@jstott.me.uk> To: <tz@lecserver.nci.nih.gov> Sent: Thursday, February 03, 2011 6:16 PM Subject: Re: lat/lon to time offset database
On 03/02/2011 18:33, Larry Ober wrote:
I'm a nubie at understanding the ins and outs of timezones so please forgive me for my potentially dumb questions.
I am looking at building a small embedded system (No OS) that will require determining the local time from the lat/lon of a location. So basically I need lat/lon to time offset from "GMT".
I had a go at doing this a few years ago when I was creating the earthtools.org website. I thought like you that it would be fairly straightforward, but no, it's really not! The result is accessed by webservice through earthtools.org, but the data is a few years old now and it's not really that accurate.
I basically generated a map of the zones as accurately as I could (limited by not having accurate administrative area boundaries) and did some processing to reduce the complexity of lookups. I blogged about it 5 years ago: http://blog.jstott.me.uk/2005/12/01/mapping-time-zones/ and http://blog.jstott.me.uk/2005/12/08/time-zone-map-completed/
If anyone has any ideas for how to improve the accuracy or, more importantly, map daylight savings time rules (which are even more complicated), I'd love to know!
Jonathan