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End of Daylight Time in US: Have you changed your camera clocks?
Gary Edstrom wrote:
For those of you who like to have correct time stamps on your pictures, remember to set the clock in your still and/or video camera to the correct time. Other clocks to consider: Kitchen Stove - Answering Machine - Still Camera - Video Camera VCR - Car - Cell Phone - PDA - Microwave - Watch - FAX Machine Central Air Conditioning - GPS GPS units are fundamentally about knowing the precise time. They get UTC from the satellites, calculate position by triangulation, and therefore can calculate local time. I have to believe that the GPS system knows all about the latest "savings time" rules all over the planet. Now, if I could just rig everything so that my GPS would use bluetooth to update the microwave, the answering machine, the stove, the camera, the VCR, etc. What's all this technology for anyway, if it can't take care of this sort of thing for me? :-) Paul Allen |
#2
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End of Daylight Time in US: Have you changed your camera clocks?
Paul Allen wrote:
Gary Edstrom wrote: For those of you who like to have correct time stamps on your pictures, remember to set the clock in your still and/or video camera to the correct time. Other clocks to consider: Kitchen Stove - Answering Machine - Still Camera - Video Camera VCR - Car - Cell Phone - PDA - Microwave - Watch - FAX Machine Central Air Conditioning - GPS GPS units are fundamentally about knowing the precise time. They get UTC from the satellites, calculate position by triangulation, and therefore can calculate local time. I have to believe that the GPS system knows all about the latest "savings time" rules all over the planet. Now, if I could just rig everything so that my GPS would use bluetooth to update the microwave, the answering machine, the stove, the camera, the VCR, etc. What's all this technology for anyway, if it can't take care of this sort of thing for me? :-) Paul Allen Some do, some don't. Mine is several years old and the local time has to be set. Gotta get one of the shiny new ones someday.... -- Ron Hunter |
#3
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End of Daylight Time in US: Have you changed your camera clocks?
"paul dot l dot allen at comcast dot net" writes:
GPS units are fundamentally about knowing the precise time. They get UTC from the satellites, calculate position by triangulation, and therefore can calculate local time. I have to believe that the GPS system knows all about the latest "savings time" rules all over the planet. The GPS *system* operates in GPS time. It marches forward at exactly the same rate as UTC, but GPS time doesn't have leap seconds, so there are always exactly the same number of seconds in a year, and so GPS time and UTC differ by an integer number of seconds. GPS receivers get GPS time from the satellites, plus a data field giving the current offset between GPS time and UTC, plus a flag indicating that a leap second is coming. So they have all the information needed to provide UTC, exactly, if they want to. But GPS receivers generally don't know what time zone you are in, because they don't include detailed maps of time zone boundaries. Once *you* tell the receiver what your local time zone is, and whether it observes daylight savings time, some receivers will handle the ST/DST switch automatically - if you're in one of the countries it's been programmed for. If any of this works, it's because of software in the receiver - the GPS system knows nothing about local time. Now, if I could just rig everything so that my GPS would use bluetooth to update the microwave, the answering machine, the stove, the camera, the VCR, etc. What's all this technology for anyway, if it can't take care of this sort of thing for me? :-) Yeah, and when the USA changes the dates that DST starts, all this technology will make the change automatically on the wrong date... Dave |
#4
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End of Daylight Time in US: Have you changed your camera clocks?
Paul Allen wrote:
Gary Edstrom wrote: For those of you who like to have correct time stamps on your pictures, remember to set the clock in your still and/or video camera to the correct time. Other clocks to consider: Kitchen Stove - Answering Machine - Still Camera - Video Camera VCR - Car - Cell Phone - PDA - Microwave - Watch - FAX Machine Central Air Conditioning - GPS GPS units are fundamentally about knowing the precise time. They get UTC from the satellites, calculate position by triangulation, and therefore can calculate local time. I have to believe that the GPS system knows all about the latest "savings time" rules all over the planet. The GPS system doesn't need to know about time zones. It is sychronized to CUT (UTC). The GPS receiver adds the offset to displayed time to reflect the local time where it is located. Now, if I could just rig everything so that my GPS would use bluetooth to update the microwave, the answering machine, the stove, the camera, the VCR, etc. What's all this technology for anyway, if it can't take care of this sort of thing for me? :-) Paul Allen |
#5
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End of Daylight Time in US: Have you changed your camera clocks?
In article , Paul Allen "paul dot l
dot allen at comcast dot writes GPS units are fundamentally about knowing the precise time. They get UTC from the satellites, calculate position by triangulation, and therefore can calculate local time. I have to believe that the GPS system knows all about the latest "savings time" rules all over the planet. Not quite true, GPS transmits GPS time with the offset to UTC (I think 16 seconds so far), this is because GPS has never implemented leap-seconds (imagine the effect of moving the position of the satellites by one second). The GPS receivers usually can usually have an offset for local time entered, maybe some will take account local time zone and DST from defined rules. -- Ian G8ILZ |
#6
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End of Daylight Time in US: Have you changed your camera clocks?
In article , George
writes The GPS system doesn't need to know about time zones. It is sychronized to CUT (UTC). Not quite, it is synchronised to GPS time. The GPS receiver adds the offset to displayed time to reflect the local time where it is located. Not quite, it adds the offset to display UTC, you have to tell it what additional offset to added so that it can display the time you require (which need not be your local mean or summer time). -- Ian G8ILZ |
#7
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End of Daylight Time in US: Have you changed your camera clocks?
Ron Hunter wrote:
Paul Allen wrote: Gary Edstrom wrote: For those of you who like to have correct time stamps on your pictures, remember to set the clock in your still and/or video camera to the correct time. Other clocks to consider: Kitchen Stove - Answering Machine - Still Camera - Video Camera VCR - Car - Cell Phone - PDA - Microwave - Watch - FAX Machine Central Air Conditioning - GPS GPS units are fundamentally about knowing the precise time. They get UTC from the satellites, calculate position by triangulation, and therefore can calculate local time. I have to believe that the GPS system knows all about the latest "savings time" rules all over the planet. Now, if I could just rig everything so that my GPS would use bluetooth to update the microwave, the answering machine, the stove, the camera, the VCR, etc. What's all this technology for anyway, if it can't take care of this sort of thing for me? :-) Paul Allen Some do, some don't. Mine is several years old and the local time has to be set. Gotta get one of the shiny new ones someday.... Yup. I discovered this morning that my old Eagle Explorer didn't have the right local time even after acquiring a location fix. Oddly, it has the ability to set the local time to whatever you want, but a cold restart caused the thing to figure out my time zone and set the local time to UTC minus 8 hours (Pacific Standard Time). My finance director's got me on a budget, so if I buy a shiny new GPS I have to forego the shiny new camera I'm hankerin' for. :-) Dang! I haven't reset my camera's time yet! I wonder what else I've forgotten? Paul Allen |
#8
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End of Daylight Time in US: Have you changed your camera clocks?
Dave Martindale wrote:
"paul dot l dot allen at comcast dot net" writes: GPS units are fundamentally about knowing the precise time. They get UTC from the satellites, calculate position by triangulation, and therefore can calculate local time. I have to believe that the GPS system knows all about the latest "savings time" rules all over the planet. The GPS *system* operates in GPS time. It marches forward at exactly the same rate as UTC, but GPS time doesn't have leap seconds, so there are always exactly the same number of seconds in a year, and so GPS time and UTC differ by an integer number of seconds. GPS receivers get GPS time from the satellites, plus a data field giving the current offset between GPS time and UTC, plus a flag indicating that a leap second is coming. So they have all the information needed to provide UTC, exactly, if they want to. But GPS receivers generally don't know what time zone you are in, because they don't include detailed maps of time zone boundaries. Once *you* tell the receiver what your local time zone is, and whether it observes daylight savings time, some receivers will handle the ST/DST switch automatically - if you're in one of the countries it's been programmed for. If any of this works, it's because of software in the receiver - the GPS system knows nothing about local time. Of course the system knows nothing about local time. And I'm pretty sure my 1997-vintage GPS receiver doesn't know anything about time zone boundaries. It also has no way for me to tell it the local offset from UTC. But, I took it out in the front yard this morning and told it to do a cold start. It thought for a while and then announced that it knew my location, the current UTC time, and the correct local time (8 hours behind UTC). How did it do that if the system didn't know how to tell it my time zone offset? Now, if I could just rig everything so that my GPS would use bluetooth to update the microwave, the answering machine, the stove, the camera, the VCR, etc. What's all this technology for anyway, if it can't take care of this sort of thing for me? :-) Yeah, and when the USA changes the dates that DST starts, all this technology will make the change automatically on the wrong date... That's why it's a mistake to embed knowledge of DST transition dates in software or firmware. Just let NTP or the GPS system take care of it. Paul Allen |
#9
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End of Daylight Time in US: Have you changed your camera clocks?
Paul Allen wrote:
Dave Martindale wrote: "paul dot l dot allen at comcast dot net" writes: GPS units are fundamentally about knowing the precise time. They get UTC from the satellites, calculate position by triangulation, and therefore can calculate local time. I have to believe that the GPS system knows all about the latest "savings time" rules all over the planet. The GPS *system* operates in GPS time. It marches forward at exactly the same rate as UTC, but GPS time doesn't have leap seconds, so there are always exactly the same number of seconds in a year, and so GPS time and UTC differ by an integer number of seconds. GPS receivers get GPS time from the satellites, plus a data field giving the current offset between GPS time and UTC, plus a flag indicating that a leap second is coming. So they have all the information needed to provide UTC, exactly, if they want to. But GPS receivers generally don't know what time zone you are in, because they don't include detailed maps of time zone boundaries. Once *you* tell the receiver what your local time zone is, and whether it observes daylight savings time, some receivers will handle the ST/DST switch automatically - if you're in one of the countries it's been programmed for. If any of this works, it's because of software in the receiver - the GPS system knows nothing about local time. Of course the system knows nothing about local time. And I'm pretty sure my 1997-vintage GPS receiver doesn't know anything about time zone boundaries. It also has no way for me to tell it the local offset from UTC. But, I took it out in the front yard this morning and told it to do a cold start. It thought for a while and then announced that it knew my location, the current UTC time, and the correct local time (8 hours behind UTC). How did it do that if the system didn't know how to tell it my time zone offset? Now, if I could just rig everything so that my GPS would use bluetooth to update the microwave, the answering machine, the stove, the camera, the VCR, etc. What's all this technology for anyway, if it can't take care of this sort of thing for me? :-) Yeah, and when the USA changes the dates that DST starts, all this technology will make the change automatically on the wrong date... That's why it's a mistake to embed knowledge of DST transition dates in software or firmware. Just let NTP or the GPS system take care of it. Paul Allen Ok for software, not so ok for firmware, and BAD for ROM... -- Ron Hunter |
#10
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End of Daylight Time in US: Have you changed your camera clocks?
"paul dot l dot allen at comcast dot net" writes:
Of course the system knows nothing about local time. And I'm pretty sure my 1997-vintage GPS receiver doesn't know anything about time zone boundaries. It also has no way for me to tell it the local offset from UTC. But, I took it out in the front yard this morning and told it to do a cold start. It thought for a while and then announced that it knew my location, the current UTC time, and the correct local time (8 hours behind UTC). How did it do that if the system didn't know how to tell it my time zone offset? Some questions: 1) What is your receiver? I'll bet it does have a way to tell it the local offset from UTC. 2) What did the receiver think the local time zone was before you did the cold start? Normally, though a cold start reloads all of the satellite-provided data, it does not reset user-provided data like the local timezone offset. 3) What do you mean by a cold start anyway? Different receivers mean different things by this. That's why it's a mistake to embed knowledge of DST transition dates in software or firmware. Just let NTP or the GPS system take care of it. But the GPS system, by design, knows nothing of local timezone boundaries, or the dates DST starts and stops. Dave |
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