Time Stamps

Former Member over 12 years ago

Back in the dark ages when I was working with my Garmin V, then later with the Quest, all my track time stamps used my home location as the reference. It didn't matteri if I was one or two time zones away in the U.S. or nine away in Europe, the timestamp was referenced to Arizona. That wasn't especially helpful, since I use these tracks for reference to determine what time I arrived at or left a supplier. Either way, I figured it had to to with my "home" icon and its time zone. In a reasonable world, the time stamp would be in zulu or GMT.

Okay, now let's move into the Nuvi/BaseCamp world, where it's not necessary to tell the device what time zone you're in -- it figures it out. Plus which, there's no "home" icon in the system. Why does it or BC or whatever still use my AZ time zone as the timestamp? This gets really strange when I'm trying to figure out when I was where, given that AZ doesn't observe DST and the rest of the world does, but at different dates -- the U.S and Europe are offset by several weeks each Spring and Fall.

Why doesn't the sytem put time stamps in either the local time where the device is, or zulu?

0 Former Member over 12 years ago

Track/Trip Log timestamps have been in UTC (not GMT) for as long as I remember. Device and PC/Mac software convert them to the timezone set (what most people care about). Thus times change with DST (as does your device/PC/Mac clock) or if you change the timezone.

BTW Windows uses UTC internally for (file etc) timestamps. They thus change twice a year in regions that have daylight saving. My guess is that Mac's do the same.

0 kganshirt over 12 years ago

If you export one of your tracks to a GPX file and take a look at it with your favorite text editor you should see that the timestamps are Zulu.

...ken...

0 FrensicPic over 12 years ago

I'm with E020443 on this. I use a GPSMAP 62s and yes, the tracklog timestamps are in GMT which is fine. I was recently in Texas and while I was there, the GPS correctly displays the local time (Central). I have the GPS set to "Automatic" for time zone. When I come back to California and look at the tracks in Basecamp, they are two hours off. I first discovered this when trying to geotag photos. The camera is correctly set for the time zone I am in but, when I return home the tracklog (as Basecamp displays it) is off. If I take a picture at 10AM in Texas, I don't care that it is 8AM in California!

It appears that Basecamp is converting the time based on the location of the home computer, NOT where the GPS was at that time. Since the GPS itself is time zone aware, why can't that info be imbedded into the tracklog so the correct local time may be displayed in Basecamp?

John

0 Former Member over 12 years ago

If I take a picture at 10AM in Texas, I don't care that it is 8AM in California!

And that is the core issue. Maybe you want to see 10am but someone else wants to see 8am. Which is correct? Both are. Both represent the same time but in different timezones.

0 Former Member over 12 years ago

And that is the core issue. Maybe you want to see 10am but someone else wants to see 8am. Which is correct? Both are. Both represent the same time but in different timezones.

I'll have to take your word for that. Personally, I see no point in BC or MS displaying anything but the time where the device was when the record was made, or for the older units, the time zone that was manually set for the device. Second choice would be zulu time. Absolutely last choice is the home base for the traveler, yet that's what I've gotten over a period of 10+ years using three different devices with vastly different capabilities with both MS and BC. I suppose when (if?) I achieve the necessary level of computer savvy I can get into the raw datafile and learn what the zulu time was, but that won't happen anytime soon.

0 Former Member over 12 years ago

Personally, I see no point in BC or MS displaying anything but the time where the device was when the record was made...

That is a reasonable position but doing that can result in the loss of information (i.e. converting all timestamps to local time upon import).

Timezones can change (with DST or otherwise) over time as countries change laws. Local time 10 years ago might not be the same as local time today. The USA changed its DST rules in 2007 so a timestamp before then may be an hour off today.

My point is that dealing with time is not as simple as you may think. I've written software that deals with it.

Here's a question. Does 2am exist on the Sun in spring when clocks go forward from 1am to 3am? If an alarm, or similar, is set for 2am every Sun what do you do on that day? Doing something at 3am may not be valid.

Here's another issue. Suppose you're traveling in timezone #1 and cross a border (state/country/etc) where local time goes forward an hour. Do you want BC to show that time shift in a recorded track/trip log. Will you be surprised to see a 1hr jump (and resulting spurious speed calculation) in that log? Suppose you go the other way and lose an hour. Now you have duplicated timestamps.

You may wish to ignore these issues. A professional programmer should not.

0 FrensicPic over 12 years ago

Maybe a feature in BC where you could set the GMT offset (time zone), including none, or GMT, that you would like for a particular purpose (recognizing STUARTMW's comments regarding time changes). The GMT in the track log would always be unaltered so, there would be no actual alteration ot the timestamps in the tracklog.

0 Former Member over 12 years ago

Timezones can change (with DST or otherwise) over time as countries change laws. Local time 10 years ago might not be the same as local time today. The USA changed its DST rules in 2007 so a timestamp before then may be an hour off today.

My point is that dealing with time is not as simple as you may think.

In my world, I care about what time it was at the place where I was using my GPS device at the time I was using it. What time it might have been if it were five years later is of absolutely no interest. If that makes me simpleminded, so be it.

In fact, where I live (AZ) takes great pride in not observing DST, and the rest of the U.S. elected to break away from the rest of the world in terms of when DST starts and ends. That makes figuring out what time I left the hotel on August 30 when I was touring England 8 years ago a real treat when all that's conveniently displayed is what time (& day) it was back in AZ.

Worrying about whether an alarm I might have set on a device in 2006 will go off at the right time this year isn't part of my problem statement.

0 Former Member over 12 years ago

In my world, I care about what time it was at the place where I was using my GPS device at the time I was using it.
There is no automatic solution to time problems caused by moving between time zones.
The best solution when out of your home timezone would be to start a "timetrack" and then immediately set a waypoint and then edit the wp description by entering the local time in that timezone when you made that waypoint. After a few seconds you can stop and save the track. That will make a gps track record that you know the correct local time for. When you know the correct local time for a particular track (timetrack) you can adjust the timezone on your computer to make that particular track (and also all the other gps data you recorded in that timezone) show the correct local time at the time and date you were using your GPS device.

0 Former Member over 12 years ago

I'm with E020443 on this. I use a GPSMAP 62s and yes, the tracklog timestamps are in GMT which is fine. I was recently in Texas and while I was there, the GPS correctly displays the local time (Central). I have the GPS set to "Automatic" for time zone. When I come back to California and look at the tracks in Basecamp, they are two hours off. I first discovered this when trying to geotag photos. The camera is correctly set for the time zone I am in but, when I return home the tracklog (as Basecamp displays it) is off. If I take a picture at 10AM in Texas, I don't care that it is 8AM in California!

It appears that Basecamp is converting the time based on the location of the home computer, NOT where the GPS was at that time. Since the GPS itself is time zone aware, why can't that info be imbedded into the tracklog so the correct local time may be displayed in Basecamp?

John

Camera times and geocoding photos can be confusing. What has worked best for me is to take a picture of the gps screen with the gps time showing when I start the track. The camera puts the camera time in that particular photo's metadata giving me a digital record of the 2 times. I subtract the 2 times and get the exact time offset between the camera time and the gps time. The coding software will have a place for me to enter that offset and all my photos will be coded correctly. Make sure the offset has the correct sign (+/-) to make the camera time match the gps time.

You will also have to set your computer to the same timezone as where you used your gps. When you open the track on your computer make sure the time at the start of the track is the same as the time showing in the photo you took of the gps screen.