On Tue, 27 Jan 2004 12:34:35 +0100, "Meindert Sprang"
wrote:

"Larry W4CSC" wrote in message
...
GPS receivers only provide 3 pieces of information. Latitude,
Longitude and Altitude....the 3 dimensions in space. All other
information (speed, heading, COG, VMG, etc.) are all derived by the
computer monitoring the changes in these 3 dimensions over
time.....many seconds. That's why it takes so long for it to change
heading or speed or VMG or other derived outputs when you make that
turn or come about.

I have heard otherwise: A GPS derives it's speed from the doppler shift on
the received carriers. A very slow averaging filter smoothes the output,
which causes the delay in indicated speed. The filter is there to prevent
erroneous speed indication due to atmospheric disurbances and multi-path
signals.

Meindert


This might be true on some $70K sophisticated survey instrument or
other, but, here at least, our discussion is about GPS operation on a
cheaply-made piece of crap sold to the boating consumer at amazing
markups, not sophisticated electronics. What you're talking about
costs serious money. You won't find that at Waste Marine where price
isn't related to quality.....(c;




Larry W4CSC

Is it just me or did the US and UK just capture 1/3
of the world's sweetest oil supply? What idiot wants to
GIVE IT BACK?!!