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

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

"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

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

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

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

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

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

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

"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