Development blog

2016-07-11 CGGTTS v1 versus v2E

Support for CGGTTS v1 output is now fully implemented. CGGTTS v1 specifies use of the full data set whereas CGGTTS v2E samples the data set with a 30 s period. In practice, the difference is small. The RMS residual difference between the two solutions in the data set below (Javad receiver) is 0.33 ns.
CGGTTS output

2016-06-30 3D model of the prototype

front view of enclosure
rear view of enclosure
Front (top) and rear (bottom) views of the prototype. The unit will have a 4x20 status display and keypad for basic control. An external DC power supply will be used.

2016-06-24 Sawtooth corrections

The effectiveness of the 1 pps sawtooth correction varies between GNSS receiver models. The sawtooth is typically designed to have a short period so that it can be quickly averaged out. In particular, at the averaging time of 780 s stipulated for a CGGTTS track, the smoothing afforded by the sawtooth correction is no longer distinguishable.

In the measurements below, the receiver's 1 pps has been measured against a caesium beam standard, for which TDEV is less than 0.5 ns for τ less than 10 000 s, and then sawtooth-corrected using the correction given by the receiver. The receivers are a Javad HE_GD, Trimble Resolution T and NVS NV08C. The Javad receiver has the most effective sawtooth correction.

Javad sawtooth
Javad sawtooth
Javad sawtooth

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