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Glitches in units and bad sat data


EraSeek
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On occasion I have heard of GPS units glitching up, freezing, or having a blank screen with a line runing through it, and people wondering what happened to their unit. I have heard an explaination of this being a result of bad data, a glitch with the satellite signal. Well this stuff does happen (as this article points out) as it did several times in Oct 2007. What I could understand of it I found interesting and could explain some of these occurences:

 

"The presence of invalid navigation message data affected different manufacturers’ GPS receiving equipment differently. Some GPS receiving equipment continued to track the anomalous signals and generate normal pseudorange measurements while “coasting” on previously collected navigation message data. Some GPS receiving equipment stopped tracking the anomalous signals altogether. Still other GPS receiving equipment fell between these two extremes. Although the signal tracking responses varied greatly, the signal acquisition responses were nearly identical. Virtually no GPS receiving equipment would be expected to be able to fully acquire the signals after anomaly onset, due to the inability to perform subframe synch and hence to resolve the 1-millisecond ambiguity of the C/A-code. However, GPS receiving equipment and associated user system logic for reacting to these effects necessarily varied on a case-by-case basis. GPS receiving equipment that had already been tracking the C/A-code signal prior to the anomaly onset, and which continued to track C/A code despite the presence of invalid navigation message data and/or default navigation message data, could have been impacted."

 

Half-way down this page: http://sidt.gpsworld.com/gpssidt/The+Syste...ategoryId=40125

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On occasion I have heard of GPS units glitching up, freezing, or having a blank screen with a line runing through it, and people wondering what happened to their unit. I have heard an explaination of this being a result of bad data, a glitch with the satellite signal. Well this stuff does happen (as this article points out) as it did several times in Oct 2007.

 

Garmin yesterday released new firmware for the three older units that had the "vertical line of death" problem and the release notes said they "updated WAAS" so maybe this is the long-promised correction to that problem.

 

Vista: http://www8.garmin.com/support/agree.jsp?id=95

Legend: http://www8.garmin.com/support/agree.jsp?id=25

Venture: http://www8.garmin.com/support/agree.jsp?id=99

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On occasion I have heard of GPS units glitching up, freezing, or having a blank screen with a line runing through it, and people wondering what happened to their unit. I have heard an explaination of this being a result of bad data, a glitch with the satellite signal. Well this stuff does happen (as this article points out) as it did several times in Oct 2007.

 

Garmin yesterday released new firmware for the three older units that had the "vertical line of death" problem and the release notes said they "updated WAAS" so maybe this is the long-promised correction to that problem.

 

Vista: http://www8.garmin.com/support/agree.jsp?id=95

Legend: http://www8.garmin.com/support/agree.jsp?id=25

Venture: http://www8.garmin.com/support/agree.jsp?id=99

 

Thanks for the heads-up. I'll have to pull out Old Blue, my semi-retired Legend, and install the firmware update.

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