Did something roll over on about Aug 19th ?

Hi Everyone,

My Sony GPS-CS1 has been misbehaving since Aug 19th. Since then it
has been recording dates in April 2030. It looks as if it is adding
0x1c00 days to the dates that it is recording.

Is anyone aware of some sort of roll-over in the GPS date format that
could have triggered this?

Is there anyone else with this device (or another device - I bet that
a lot of the code is shared) who has seen the same problem?


Many thanks, Phil.

On Aug 29, 8:27=A0am, "spam_from_goo...@chezphil.org"

The problem is in your equipment, not with the GPS system.

From ICD-GPS-200E (1.5 MB file available at http://www.gps.gov/technical/i=
cwg/IS-GPS-200E.pdf
):

"6.2.4 GPS Week Number. The GPS week numbering system is established
with week number zero (0) being
defined as that week which started with the X1 epoch occurring at
midnight UTC(USNO) on the night of January 5,
1980/ morning of January 6, 1980. The GPS week number continuously
increments by one (1) at each end/start of
week epoch without ever resetting to zero. Users must recognize that
the week number information contained in the
Nav Message may not necessarily reflect the current full GPS week
number (see paragraphs 20.3.3.3.1.1,
20.3.3.5.1.5, 20.3.3.5.2.4, and 30.3.3.1.1.1).

20.3.3.3.1.1 Transmission Week Number. The ten MSBs of word three
shall contain the ten LSBs of the Week
Number as defined in 3.3.4. These ten bits shall be a modulo 1024
binary representation of the current GPS week
number at the start of the data set transmission interval (see
paragraph 3.3.4(b)). The GPS week number increments
at each end/start of week epoch."

The GPS broadcast signal represents Week Number with only 10 bits, so
it's ambiguous modulo 1024.

Today (August 29, 2010) is Day 1 of Week 1599. The broadcast data is
575 (1599 mod 1024).

14 April 2030 is Day 1 of Week 2623 (which mod 1024 is also 575).

28 November 2049 is Day 1 of Week 3647, and could also be inferred.

The day of the week is implicit in the GPS time, which is time of
week, not time of day.

You should contact Sony.

http://esupport.sony.com/US/perl/model-home.pl?mdl=3DGPSCS1

http://esupport.sony.com/US/perl/contact-land.pl?mdl=3DGPSCS1

http://esupport.sony.com/US/perl/support-contacts.pl?mdl=3DGPSCS1

Thanks for the info Ed.

Luckily for me I'm using my own code to process the logs that I get
from the device, so it's easy to adjust having worked out what's going
on.

This device has been superseded by a device that is less useful for
me; the GPS-CS1 uses an AA battery so I can take it with my up a
mountain with one battery per day and not have to worry about
charging. Sony's replacement device, and most other loggers, either
have a less useful battery or save data in a less-useful format. I
will complain to Sony about this, but the most generous solution I can
imagine is an offer of the new (and to me less useful) device as a
replacement.

Cheers, Phil.

Thanks for the info Ed.

Luckily for me I'm using my own code to process the logs that I get
from the device, so it's easy to adjust having worked out what's going
on.

This device has been superseded by a device that is less useful for
me; the GPS-CS1 uses an AA battery so I can take it with my up a
mountain with one battery per day and not have to worry about
charging. Sony's replacement device, and most other loggers, either
have a less useful battery or save data in a less-useful format. I
will complain to Sony about this, but the most generous solution I can
imagine is an offer of the new (and to me less useful) device as a
replacement.

Cheers, Phil.

On Aug 30, 11:11 pm, "spam_from_goo...@chezphil.org"

Huh. Well, I got as far as typing in my enquiry in their web form,
but when I press "continue..." it does nothing at all. Is it just me,
or has the Web just fallen apart in the last year or so? I now seem
to have only about a 50% success rate with online shops, etc.; it's
worse now than at the height of the "optimised for Internet Explorer
era".