[time-nuts] Building a GPSDO & trouble using Jupiter-T

Chris Albertson albertson.chris at gmail.com
Wed Feb 1 23:17:58 UTC 2012

> 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.

> 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.

Chris Albertson
Redondo Beach, California

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