Yesterday I was on a walk by the Thames I uploaded the trace(to 0sm) but the bit near MI6 building was way off,My Garmin Vista Hcx is usually good as gold in the country.But is it the tall buildings? I suppose the south bank is shadowed by them, considering most satellites are further south or it someting to do with MI6. anyone else found this? any ideas?

asked 20 Mar '11, 13:05

andy%20mackey's gravatar image

andy mackey
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edited 08 Apr '15, 15:32

aseerel4c26's gravatar image

aseerel4c26 ♦
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sorry vauxhall bridge not westminister

(21 Mar '11, 20:00) andy mackey

(as I'm sure you're aware, but other people may not be) the Vista Hcx does report a "location +- X m" figure on the "Satellites" screen. I turn to try the "IT Crowd fix" (turn it off and on again) if that +- figure is more than I'd normally expect.

Re the "South" bit GPS satellites aren't geostationary (see obligatory wiki link) so a tall building (or hill) on any side could impair reception.

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answered 21 Mar '11, 13:16

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SomeoneElse ♦
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Thanks both of you, I hadn't actually registered the plus/ minus on the walk, I did notice on the installed OSM map I was in the water but thought it was a mapping error but later found map was good, and the trace was at fault,it was just 50 meters NE of vauxhall bridge and trace was uploaded at 21-08 hours on 19th for any body who want to have a look.

(21 Mar '11, 19:58) andy mackey

Yes, I guess you got problems because of reflections. Tall buildings can reflect the gps signals which then take longer to reach your receiver (and will result in wrong positions). Maybe you wanted to hear that MI6 scrambles gps frequencies for defence reasons?

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answered 20 Mar '11, 20:27

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dieterdreist
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edited 20 Mar '11, 20:31

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question asked: 20 Mar '11, 13:05

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last updated: 08 Apr '15, 15:32

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