Performance and Progress Report - John Doe FIX: put in the authors ...

accuracy is likely to be on the order of a few hundred microseconds, depending on
computer speed and loading. The uncertainty in developing a timestamp from software,
even using hardware oscillators, can be significantly higher than the hardware
uncertainty. The estimate of this uncertainty is on the order of 10-20 microseconds
depending on computer speed and loading.
Experiments were also done (with Andy McLeod) that demonstrated that an
implementation of this approach over commercial wireless is limited in accuracy due to
variable latency in the wireless switches, on the order of 1-5ms rms, with some spikes to
10ms. In support of this approach, Calder has developed code, termed the Software
Grandmaster (SWGM) Algorithm, to synchronize, syntonize and absolute reference PTP
time to a UTC master, in particular the 1PPS and ZDA messages from a GPS or IMU.
The short-term accuracy of this system is typically 100-110ns rms from master to slave
(slightly better on the master), and the long-term stability is essentially that of the GPS or
IMU system itself. That is, SWGM-derived hardware times track UTC time absolutely
within 100-110ns rms as long as the system remains in operation. The SWGM algorithm
is robust to network packet loss up to ~60% and the a priori uncertainty estimated for
timestamps by the SWGM algorithm match the true errors observed in the test
environment. The self-timing of software latency is possible using processor register
timing and careful control of process priority, but that process priority can significantly
affect likely uncertainty in timestamping (by an order of magnitude or more).
This approach was tested in the field using launches from the NOAA Ship THOMAS
JEFFERSON and the Klein 5410 phase measuring multibeam sonar in collaboration with
work being carried out by de Moustier, Glynn, and Huff. The success of this approach
has led to discussions with Industrial Consortium partners (SAIC, Reson and Applanix)
on the potential for test implementations of the PTP and SWGM algorithms in their
survey systems. An agreement has been reached with NOAA (Brennan), Applanix
(Canter) and Reson (Malzone) to test this as a US Hydro 2007 paper, using POS/MV 320
V4, Reson 7125/7-P and the NOAA Ship BAY HYDROGRAPHERS.
NEW APPROACHES TO MULTIBEAM AND SIDESCAN
SONAR DATA PROCESSING
IMPROVED BATHYMETRIC PROCESSING:
CUBE and Improved Uncertainty Management:
One of the major efforts of the Center has been to develop improved data processing
methods that can provide hydrographers with the ability to very rapidly and accurately
process the massive amounts of data collected with modern multibeam systems. This
data processing step is one of the most serious bottlenecks in the hydrographic “data
processing pipeline” at NOAA, NAVO, and hydrographic agencies and survey
companies worldwide. We have explored a number of different approaches for
automated data processing (see earlier progress reports for descriptions of these
approaches) and, over the past three years focused our effort on a technique developed by
JHC Performance Report 26 30 January 2007