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Author Topic:   GPS Devices Might Stop Working This Weekend -- Week Number Rollover
PaulK
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Posts: 17822
Joined: 01-10-2003
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Message 13 of 22 (850614)
04-11-2019 8:48 AM
Reply to: Message 12 by Percy
04-11-2019 8:32 AM


Re: A Failure in New York City
The obvious change would be adding 3 more bits to the counter. So it lasts 8192 weeks before rollover instead of 1024.

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PaulK
Member
Posts: 17822
Joined: 01-10-2003
Member Rating: 2.2


Message 18 of 22 (850630)
04-11-2019 11:33 AM
Reply to: Message 16 by Percy
04-11-2019 10:57 AM


Re: A Failure in New York City
GPS was designed for the capabilities of embedded systems more than 40 years ago. So it is not entirely surprising that they tried to squeeze memory. Available memory would be measured in kilobytes at best - certainly not the gigabytes of a modern smartphone.
I can’t say whether they had 3 unused bits in the (16 bit?) word or whether they repurposed one or more of them. But it seems likely to me that they stopped with 13 bits because they couldn’t add any more.

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