[OZAPRS] RE: ozaprs Digest, Vol 5, Issue 11

Darryl Smith Darryl at radio-active.net.au
Tue Jun 24 12:34:17 EST 2003

Robert Commented
>>case the GPS set the position EXACTLY 5 degrees west of where it should
>>be... In the other case it was EXACTLY 36 degrees north.
>Perhaps multipath error on the GPSR is to blame?  This often 
>accounts for unusual top speeds or positions.

I do not suspect that multi-path or antenna problems are the cause in this
case. What normally happens in multi-path is that the Kalaman filter will
tend to pull the position off, at some angle. Thanks to the filter, it is
extremely unlikely that multi-path will only affect one axis.

The other thing is that only the degrees were incorrect, not seconds and
minutes. If there was an issue with the multi-path, the entire number
have been off. That said, in most cases I think that Multi-Path does cause
lot of the problems... I just have this image in my head of placing a
antenna on a vehicle you are attempting to track, with a Choke Ring of 12"
diameter and 2" deapth to reduce the multipath...

By the way, cool book... Great work.


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