Welcome to the NavList Message Boards.


A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding

Compose Your Message

Add Images & Files
    Re: Possible GPS Date Rollover problems week of April 6, 2019
    From: Paul Hirose
    Date: 2019 Mar 30, 14:41 -0700

    The origin of the GPS time scale is 1980 January 6 00:00:00 UTC =
    00:00:19 TAI = Julian date 2 444 244.5 + 19s TAI.
    A week number rollover occurs every 1024 weeks, and this will be the
    second rollover in GPS history, so add 2 * 7 * 1024 days to obtain JD 2
    458 580.5 + 19s TAI = 2019 April 7 00:00:19 TAI.
    Until the next leap second, UTC is 37s behind TAI. Therefore, April 7
    00:00:19 TAI - 37s = April 6 23:59:42 UTC. That's when the rollover occurs.
    Today I tested a 1994 Magellan Trailblazer, one of the first affordable
    GPS receivers. It was unable to produce a position, even after more that
    30 minutes. The date it displays is in August 1999, but its UTC time of
    day is only a few seconds off.
    1999-08-14 20:56:08 = displayed UTC
    0 = cycle number
    1022 = GPS week
    593781.00 seconds
    2019-03-30 20:56:00 = correct UTC
    1 = cycle number
    1022 = GPS week
    593778.00 seconds
    "Cycle number" is the number of whole 1024-week cycles of GPS time that
    have elapsed. The week numbers are identical and the seconds since the
    beginning of the GPS week differ by only 3.

    Browse Files

    Drop Files


    What is NavList?

    Join NavList

    (please, no nicknames or handles)
    Do you want to receive all group messages by email?
    Yes No

    You can also join by posting. Your first on-topic post automatically makes you a member.

    Posting Code

    Enter the email address associated with your NavList messages. Your posting code will be emailed to you immediately.

    Email Settings

    Posting Code:

    Custom Index

    Start date: (yyyymm dd)
    End date: (yyyymm dd)

    Visit this site
    Visit this site
    Visit this site
    Visit this site
    Visit this site
    Visit this site