Actually, the velocity vector and hence vehicle direction is the residual of the satelllite signal doppler solution. The doppler component for each satellite signal can be calculated knowing the satellite location at the time the signal was transmitted (calculated from the ephemiris for each satellite) and the user equipment's current position. What is left over is attributable to the users velocity. This is far more accurate and less noisy that differentiating position, as was done with previous radio navigation systems such as Loran or Omega.

One place that would help in gpsapp would be to retain the last heading from the GPS as it is slowing down, as the heading becomes quite noisy at rest. Typically if you lock the direction pointer as you drop below 1-2 km/hr and restore as you speed up again it provides a cleaner display for the user.

The active copmponent of the microstrip antenna (sometimes called a patch antenna) supplied with the SV6 from BG Micro is the plating on the exposed surface of the square piece of ceramic. Mine is under a piece of foam tape. The other side is actually a preamp in a shielded enclosure with about 25-30 db of gain, powered by 5 vdc on the feedline. If you are getting anything with the antenna upside down then it is just good fortune and reflections. The "T" section of extruded black plastic is just for mounting.

Lynn