Wind information

Throughout this season I've flown with several friends that use
different instruments that calculate wind information while in flight.

I use a GPS driving a PDA running LK8000 (I don't use the new true
wind function). Ron uses an SN-10, Dan uses a PDA running Seeyou and
getting wind information via GPS and the Tasman FP module, Brian uses
an iPAQ 310 running Seeyou and using only GPS wind (internal GPS
chip).

My observations are that generally we are all within 2 to 7 knots and
5 to 15 degrees of speed and direction off when we report to each
other what we are seeing at that moment. The guys using GPS only have
the widest spread and the guys using pitot/static/GPS seem to be
closer and I feel more accurate. However even with my GPS driven wind
I still feel fairly confident that it is giving me very useful
information. I.E. coming back off the flats in Eastern WA heading into
a strong headwind it was nice to know the ridge up ahead was going to
give me ridge lift when I got to it.

I also think that since when we report the wind info to each other, we
are spread out across a large area of sky and the winds could very
well be different, so maybe there isn't that large of a difference due
to calculation methods after all. In the foothills/mountains there can
be large local airmass difference due to orographic, local flow,
valley flow, etc..............

Anyone have any thoughts on this foggy morning rambling?

Brad