60km off position

skyeye over 2 years ago

very rare situation I got on one of our trackers yesterday.

tracking in 10min interval, one point suddenly was 60km of the approximate location the device

The next trackpoint after other 10min was again near estimated position.

I know it is not so abnormal, just want to mention this in case someone would experience similar situation.

0 twolpert over 2 years ago

Conditions at the off-position location? Bad sky view?

0 Jordan249 over 2 years ago

Probably jammed by U.S. military during their testing if near Yuma Arizona or other listed locations below.

www.navcen.uscg.gov/.../GPS_Interference.pdf

www.gps.gov/.../

www.navcen.uscg.gov/gps-service-interruptions

0 skyeye over 2 years ago in reply to Jordan249

no, sky view OK

I have experience with some time 'jumps' from my work with tracking of rail cars and containers. We had experienced few time jumps, having hundreds of mobile receivers and many thousands of data each year. OK it is nw some years ago, but still I know all did behave similar, our database got confused and when we looked into our receivers, clearly we could see sudden time jump there.

Jordan249 might be this time closer to solution I think, but why need this be in Arizona or other places in US, why in America? ;-)

There are today other boys who feel the need for playing....

0 twolpert over 2 years ago in reply to skyeye

Jordan249 is referring to US military GPS testing, which is designed to interfere with civilian GPS reception over limited areas and limited timeframes. It is not global (not a rollback to the bad old days of selective availability). It doesn't apply to Switzerland :-)

What do you mean by time jump?

0 skyeye over 2 years ago in reply to twolpert

yes, I understood all. Meaning was that boys trying to play with GPS exist also in other areas of the world, in recent times they play more often ;-)

As far as time jump concerned, I have not access to any device log any more, but when we had lot of devices, we had simply wrong time/date at same time. This did happen sometimes and even lead sometimes to crash and confusion of our database which was the base for our server similar to explore website. The server presented then similar jumps like this one. Analysis of internal storage of few of our reference receivers did show wrong time calculation between two correct calculations.

0 twolpert over 2 years ago in reply to skyeye

If you look at the out of position point on the Explore web site, is it (roughly) on the expected 10 minute mark?

Otherwise, what you describe would be typical of errors introduced by multi-path. But with a good sky view, that's not it.

0 skyeye over 2 years ago in reply to twolpert

actually I tried now to estimate, it i some 80km far away. The time fits about the 10min sequence roughly.

And yes, multipath is common, but probably not in such amount, I did so far experienced jumps of few kilometers. Big jumps I have seen only when devices had in their logs time jumps, calculated time and date completely out of any possible value, quite over whole Europe. As I have disposed off last devices I could access some internal logs, I can not tell exactly, but remember such disturbances occasionally.

What I wanted say otherwise, jamming is not alone play field for Arizona. World is big and others in other parts of the world want play too. I tend follow therefore rather the Jordan249 version, but not Arizona

Can not tell you more here