Slightly off this thread topic, but what formula do you use to calc the XTE?

I've used a variation of Ed Williams' formula "XTD
=asin(sin(dist_AD)*sin(crs_AD-crs_AB))" but if I run my calcs in parallel
with a GPS they are consistently different with the GPS numbers varying
considerably more than mine.

"John Bell" wrote in message
...
I got interested in the effects of homing on a waypoint as opposed to
tracking. I have seen the illustrations and have understood the concept
for
some time, but I have never seen any numbers. If you are interested here
is
the results of my playing around with Excel:

http://www.cockpitgps.com/other_arti...rack_error.htm

John Bell
www.cockpitgps.com
www.smallboatgps.com