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Spirent KB Article
Doc ID: FAQ10337
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Positioning Application: Loading a GPS almanac has set the wrong satellite orbital reference time
On Sunday August 22nd 1999 the GPS week number in the navigation message rolled over from 1023 to 0.
The WEEK values in YUMA format almanac files also rolled-over. Thus if a user downloads a YUMA almanac file the week number alone cannot determine the intended reference time of the orbital data.
PosApp will assume the current rollover value of 1, by default, but this may not necessarily be the required setting.
You can manually edit the week rollover value when loading an almanac file via the GPS constellation file 'Load orbits from file' control.
You can also adjust the week rollover value to affect the scenario start time, using the "Start time" control panel.
Product : SimREPLAYplus,SimGEN,PosApp