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

Magnus Danielson magnus at rubidium.dyndns.org
Wed Feb 1 23:32:05 UTC 2012

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.


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