On Mon, 15 Mar 2004 19:49:16 -0800, "BTIZ"
wrote:

GPS only computes heading from "last known position" to "current position",
if you are not walking.. the "last known and current" are the same.. there
is no heading to compute.. granted with minor errors of cheap handheld GPS
units.. the "movement" could be minor inches or parts of an inch as the GPS
computes it's position.. and that will cause a heading change..

It is actually quite a bit more than inches. Single carrier civilian
GPS without SA (which has been shut off for several years now) is
accurate to about 10-20 meters. With WAAS corrections, it is about 3
meters.

The delta between any two position estimates is several inches to
several feet. Most GPS software will mask this motion and force the
velocity display to 0.0, and the heading display to be fixed, however,
if the delta between two position estimates is large enough, it can
generate a false movement.

-Nathan