Reply to post: RTFM

Fun fact: GPS uses 10 bits to store the week. That means it runs out... oh heck – April 6, 2019

Rich Webb


Too much FUD being spread here. Read the fine manual, specifically IS-GPS-200. The GPS ephemeris message (Message Type 10) has a 13-bit field for the GPS week: " Transmission Week Number. Bits 39 through 51 of Message Type 10 shall contain 13 bits which are a modulo-8192 binary representation of the current GPS week number at the start of the CEI data set transmission interval (see paragraph 6.2.4)." And no, that field wasn't added just last year. One might additionally speculate that there may be additional fields with a longer span outside the domain of IS-GPS-200 but even a rollover after some 150 years is probably adequate for practical purposes.

Yes, it's entirely possible that some poor coder relied on the 10-bit week number (there are also fields which represent the week number in 8 bits i.e., modulo 256! Panic!!!) but there's no excuse for having done so.

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