Time to acquire a lock was a major concern for my VSS project. However one of the things I like about this manufacture, they seem to have some pretty smart engineers. The custom Harley crowd swears by their digital gauge clusters and speedometers. The engineers used two theories to overcome the normal acquisition delay and signal loss problems.
First, it attempts to never lose the GPS position lock. While part of the circuit sleeps when key is off, but the GPS chip is always kept active, so it has zero lag time on start up. A small red LED flashes every 30 seconds or so to show it's working.
Second, they added an accelerometer chip to the circuitry, and some pretty darn good logic to boot. If does lose the GPS signal, it switches over to the accelerometer for calculating speed data until GPS lock is recovered. Kinda like having a G-Tech unit built in.. Most modern factory automotive in-dash Nav units also employ this technique to deal with tunnels and such now. It knows you were last moving at XX mph, and if your speeding up or slowing down.
I had forgotten about it having the ignition switch connection in my post above. But also that it has cruise control capabilities built in. The manual for this thing is actually a "good read"
I mounted it under the dash where is has partial view of the sky. Next to my OBDII plug. The dash covering it is 3/4 plywood laminated with fiberglass and gelcoat. I'm amazed it works so well without a remote mounted antenna, or good line of sight.
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