View Full Version : GPS Time setting.

4th June 2008, 07:46 AM

I'm pretty new to this technology and don't own a receiver of any kind. I am however trying to design a device which has a gps component to it and have a question. Can any of the gps chips or receivers set their own local time? The car based ones I've looked at in the shops all have an initial setup process where you have to tell it which time zone it's in. This is baffling as it knows which street it's in so why doesn't it know which time zone it's in? If in fact this is possible then what about daylight savings?

Any advise on this would be greatly appreciated.


4th June 2008, 11:15 AM
The GPS can use the satellites clock which is atomic clock acurate. I have a function on my gps equiped pda that syncronises the pda's time with the satellites time.
Therefore, yes ,the gps has the hardware to know the time where it is. It just needs the appropriate software to display it.

4th June 2008, 11:32 AM

I wonder why all the vehicle based ones don't do it.. Does your's update according to daylight savings time too or do you have to adjust that manually?

4th June 2008, 07:25 PM
I know my Garmin 60CSx can also adjust for Daylight savings (yes|no|auto).
I think you would need to program the device with the time zones (and their offsets) and then use the gps position data to locate itself within a time zone and apply that to the UTC time. You would probably need to code the daylight saving periods and account for Northern/Southern hemisphere differences within the same time zones? I don't think the satelite data includes any offsets at all - probably all done in the unit itself?


29th May 2009, 07:40 AM
I have a feeling the Oregon might be able to do it, but don't quote me,
and it's a handheld.

Yes, the software has to have a time zone map, and calculate the offset before displaying the time,
and would need current worldwide daylight savings information to be entirely accurate.

It would be easy if you could just divide the Earth's 360 degrees of longitude by 24, but since time zone borders are so irregular, there's no way to generate the map in a dynamic way.

I wrote a clock program that supports this (except daylight savings) a while back:
it displays the feature visually to a Human.

29th May 2009, 02:44 PM
The last Silicon Chip magazine has a project to make a clock that derives its accuracy from a GPS chip, it might be worth having a read.

31st May 2009, 07:07 PM
I have some GPS floating around that I could sell at really cheap prices, not new necessarily.