Thanks for all the replys.  I got about 20 yesterday.  Here are some responses.

The reason I am making 2 measurements is to eliminate the speed of sound
from the equation, as many have suggested.

Got many good responses about the temperature idea which made it much easier
than I was planning.

The article I saw on this had a different configuration of the ultrasonic
tips.  They used 3 prongs arranged in a equalateral triangle so three paths
will be used to get the wind vector.  They did this because the four prong
configuration creates turbulance along one of the paths if the wind
direction is parallel to this path.  This turbulance causes errors.  I am
not looking for a super precise answer, so I am settling with four prongs
for easier math.  I just want to know if I can go boating or not.

I got a few replys about having the electronics in the cottage and using
variable frequency pulses for display of wind magnitude, and am rethinking
that.  I don't want to have to deal with echos on the line, plus frequency
displays are pretty expensive.

I am looking for some ideas on how to do this.  What about PWM?  I having
had much experience with transmitting data over distances, so I don't know
the best way to do this.  I need to display the wind magnitude and the
direction.

Thanks for all the help!

P.S.  The article is in "Sensors:The Journal of Applied Sensing Technology",
May 1996, Vol. 13 No. 5

   Donald Frederick Wright Jr.

   School info: Lawrence Technological University
   E-mail: DW79208@LTU.EDU

   Work Info: AVL North America
   E-mail: DNWRIGHT@AVLNA.COM