[time-nuts] Low cost GPS module for < 100ns timestamping error

[Mark Sims]

The Neo-6M based module (Crius CN-06) is available from HobbyKing for $20 (sometimes on sale for $16).  You do have to add the wire to access the 1PPS signal.
In my testing,  I prefer it over the Adafruit Ultimate GPS.   The Neo-6M seemed to a a little more sensitive (could get reliable lock and tracking sitting on the floor of a 2 story stucco house (stucco over wire mesh) away from any windows and did not have issues with reporting fixes of a rather stationary antenna - the Adafruit module would fake a fixed position if it was not moving).  I did a little testing of the 1PPS output and it seemed to be quite good.
My application was mainly driven by the desire to calculate the range and bearing between two units spaced 100 feet to a couple of miles (using an Xbee radio link).  I could move a unit in a circle a couple of feet radius around another one and get good range/bearing info...  not too shabby for a $20 hockey puck.