Drudge Retort: The Other Side of the News
Friday, April 05, 2019

Satellites will reset their onboard week counters to zero this Saturday, and that could leave some older GPS receivers unprepared for the change and potentially out of sync with other systems. The 24 satellites operated by the U.S. Air Force that make up the GPS system provide longitude, latitude and altitude measurements to users on Earth.

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I have an old GPS handheld device from 1993 or so. I may just fire it up and see how it deals with the change.

#1 | Posted by LampLighter at 2019-04-05 02:08 PM | Reply

I found an old gps we had for our sailboat and tried using it about a year ago for making tree stand waypoints. It was an early to mid 90's model.
It couldn't find any satellites.

I've since thrown it out but I googled everything trying to find a way to update it but no dice.
Good luck with yours, and don't forget to update us.

#2 | Posted by 101Chairborne at 2019-04-05 02:14 PM | Reply | Newsworthy 1

I have an old GPS handheld device from 1993 or so. I may just fire it up and see how it deals with the change.
#1 | Posted by LampLighter

Ooh, and the maps have never been updated? That should be extra fun if you try to use it for a bit of navigation. I wonder how it accurate it is considering that 1993 GPS was ~100yds in error, and in 1999/2000 the error shrank to around ~10yds or less.

#3 | Posted by GOnoles92 at 2019-04-05 02:14 PM | Reply


@#3 ... the maps have never been updated? ...

Maps? What maps?

It gave me time, lat, lon and if it could find a fourth satellite, altitude, on a text display.

Icom GP-22

Image is here:
retro-gps.info

#4 | Posted by LampLighter at 2019-04-05 02:50 PM | Reply


After 5 minutes of looking, it found 3 satellites.

The time it is displaying is correct to the second (probably better than a second, but that is all I can check it to using WWV on my shortwave receiver).

I'm going to let it run for a while more to see if it picks up more satellites.

fwiw, the Duracell alkaline batteries in the box had a use-by year of 2010, so I guess It's been a while since I used it. ;)

#5 | Posted by LampLighter at 2019-04-05 03:05 PM | Reply


While it got the time correct, it thinks the current date is August 20, 1999.

#6 | Posted by LampLighter at 2019-04-05 03:27 PM | Reply

I intentionally don't use directions on my phone because I hate being dependent on it. I look at the map, figure out to get where I'm going and do it the old fashioned way. If I get lost I consider that a learning experience to help me remember next time I go there.

I do realize, of course, that if the satellites have an issue me finding a restaurant I want to go to will be the least concerning outcome.

#7 | Posted by jpw at 2019-04-05 04:54 PM | Reply

"I intentionally don't use directions on my phone because I hate being dependent on it."

I think that is a guy thing. Guys don't like to ask directions from people and apparently even from computers. WE feel stupid or then they will knw e are not from around here...maybe we don't want our computers to know how stupid we REALLY are?

I don't know... I just know that if you find me wandering it doesn't mean I am lost. Yet. I just haven't figured out where I am going!

And lately...I have noticed...it doesn't really matter. As long as you are Going Somewhere and not going Nowhere!

#8 | Posted by donnerboy at 2019-04-05 05:05 PM | Reply

August 20, 1999

That is the date it "reverts" to Zero...

#9 | Posted by AndreaMackris at 2019-04-05 10:26 PM | Reply

Its like Epoch Time, but GPS only has 10bits to encode Week, so every 1024 weeks it needs to "roll over" ..

But I am trying to understand why it would triangulate.

Pre-1993 GPS software may have a an issue.

#10 | Posted by AndreaMackris at 2019-04-05 10:31 PM | Reply

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Today the GPS was showing the correct time once again, but the date is Aug 21, 1999.

The 10-bit counter is being expanded to 13-bits, allowing for 8192 weeks (about 157 years) between rollovers.

#11 | Posted by LampLighter at 2019-04-06 02:34 PM | Reply | Newsworthy 2

Interesting ... about the 13 bits ...

But I am trying to understand why it would triangulate.

That should be "wouldn't"..

#12 | Posted by AndreaMackris at 2019-04-06 02:43 PM | Reply

#11 | POSTED BY LAMPLIGHTER

So it seems its been in new message types, so I am not sure why a firmware update, not just the maps, would read these.

Also I read some receiver manufactures use the compile time for Epoch start date/week.

So some GPS units won't display the EoW reset until 20yrs or so out from manufacture, that's pretty clever.

#13 | Posted by AndreaMackris at 2019-04-06 02:51 PM | Reply

wouldn't read these new message types.

#14 | Posted by AndreaMackris at 2019-04-06 02:51 PM | Reply


My unit triangulates fine, once it finds enough satellites.

It just seems to be the date that is off.

btw, to give you a sense of 1993 technology...

Once it finds enough satellites, there is a 2 minute delay before it finishes calculating the lat/lon and displays the info.

If I haven't used it in a while, that 2 minute wait increases to 10 minutes because it first needs to obtain an "almanac" before it can do the calculations.

I suspect the current GPS units have a bit faster CPU running inside of them...

#15 | Posted by LampLighter at 2019-04-06 02:58 PM | Reply

#15 | POSTED BY LAMPLIGHTER

If I haven't used it in a while, that 2 minute wait increases to 10 minutes because it first needs to obtain an "almanac" before it can do the calculations.

That is just the nature of the tech, from what I recall.

I suspect the current GPS units have a bit faster CPU running inside of them...

They can give you a position quickly, but the precision is low, but its good enough for phones.

The stuff I worked on was with error predictions and correction, especially tunnels. Sats have a strength value as well for the receivers location, and using that and a custom DOP calculation as input, my design would predict the GPS precision/error in the future, which was fed into a Kalman filter along with 3d accelerometer, and barometer to produce an alternative location and altitude. This was back in 2007-8.

#16 | Posted by AndreaMackris at 2019-04-06 03:13 PM | Reply

@#16 ... That is just the nature of the tech, from what I recall. ...

It wouldn't surprise me if the "almanac" concept is part of the protocol.

For the two-minutes thing, maybe my unit just waits until it obtains the full degrees/minutes/seconds resolution before it displays anything.

Newer units I've seen display the info much more quickly, though I've not done a side-by-side comparison to see how the relative accuracy/resolution/precision holds up.


#17 | Posted by LampLighter at 2019-04-06 03:27 PM | Reply

My question is, why did they use an odd-ball like a 10-bit integer for their 'clock'? If they had used a 16-bit integer, this would have never been an issue. I hear though that the latest satellites are using 13-bits, which still seems to be a bit of an odd-number, both literally and figuratively ;-)

OCU

#18 | Posted by OCUser at 2019-04-06 09:05 PM | Reply

13-bit definitely seemed like an unusual choice to me. Anyone know if it's used for anything else?

#19 | Posted by GOnoles92 at 2019-04-07 02:20 AM | Reply


#18 ... My question is, why did they use an odd-ball like a 10-bit integer for their 'clock'? ...

Oh that's an easy one.

Those who create the amazing technology often underestimate the earth-shattering extent of their creation.

For example, the Internet.

Originally conceived with 32-bit addresses. That is, only 2 billion or so entities on the internet.

Wow, who would have thought in the 1970's that people would be on a global network? Bring yourself back to the 1970's and try to envision global computer networking. Those guys who envisioned the Internet were amazing.

But even they did not imagine the scope of their invention.

Who wudda thunk that more than 2 billion "things" would want to connect to this new Internet network?

That's a summary, a very very short summary.


#20 | Posted by LampLighter at 2019-04-07 02:41 AM | Reply


In 1969 NASA put people on the moon, and returned them safely back to Earth, with less computing capability,much less, than is in the phone you have in your pocket.

Think about that.

That is what Scientists and Engineers do.

#21 | Posted by LampLighter at 2019-04-07 02:46 AM | Reply


@#19 ... Anyone know if it's used for anything else? ...

My opinion: that was an appropriate solution to the problem that needed to be solved.

Do you disagree with 13 bits, if so, why? That's the engineering approach.

(and an aside, this is the second time I had to type this response due to a duly-reported {and apparently ignored} bug on this site that deletes comments. This site bug is getting tiresome.)

#22 | Posted by LampLighter at 2019-04-07 02:55 AM | Reply

That's a summary, a very very short summary. #20 | POSTED BY LAMPLIGHTER

Then the engineers came up with IPv6, and someday we'll all be using that for networking :). Enough addresses for every atom on earth, with some leftover!
No real problem with 13bit for GPS, but it seems like an abnormality whereas 10/1024, or 32 are all commonly used formats for digital communications and hardware.

#23 | Posted by GOnoles92 at 2019-04-07 01:23 PM | Reply

and an aside, this is the second time I had to type this response due to a duly-reported 22 | POSTED BY LAMPLIGHTER

I have encountered that one too, but I appreciate the responses.

#24 | Posted by GOnoles92 at 2019-04-07 01:24 PM | Reply

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