On 02/02/12 00:17, Chris Albertson wrote:
If you do not limit yourself to NMEA you can get L1/L2 C/A and P-code and
both code and carrier phase in rates higher than 1 Hz. I have such
receivers, and you can get them as modules.
NMEA was designed for boat navagation and works well for that. I
don't need NMEA for timing. What can I look for that is in the About
$100 range and can receive L2.
Achieveable but a bit rare.
From one second to the other, you usually do not change speed or direction
that much. Your typical receiver will produce both position and velocity
vector, so Kalman filtering on that isn't too hard.
In a car you can be out of GPS coverage for a long time. Tunnels and
parking structures are obvious but also tall buildings on both sides
of a street and even trees. You could be out of GPS for many minutes
at a time so odometers, compass and gyros are helpful. On my
sailboat autopilot the GPS was supplemented by a compass, water speed
sensor and gyro because GPS knows only position and not orientation.
That's why my car-GPS uses accelerometers as additional aid. I also use
a GPS antenna on top of the car for best possible reception when I can
see birds.
Cheers,
Magnus
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