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P/N 95P-6001-00 (October 2020) Wayfinder DVL Guide
Page 14
EAR-Controlled Technology Subject to Restrictions Contained on the Cover Page.
Ping Timing
It is usually desirable to minimize the time it takes a Wayfinder to complete a ping cycle because this ena-
bles faster data update rates. When the maximum operating altitude is known, the
Max Range
setting on
the
System tab
can be used to limit the maximum ping time in Bottom Track mode, since time to receive
data from the bottom is proportional to the distance to the bottom.
For example, if you know the maximum depth in the deployment area is 40 meters, set the value slightly
larger than 40 m, say 45 m, instead of default 60 meters. Now if the Wayfinder loses track of the bottom,
it will stop searching for the bottom at 45 m rather than spend time searching down to 60 m.
Table 4 shows the approximate Bottom Track ping times for a Wayfinder DVL as a function of altitude
above the bottom.
Table 4. Approximate Bottom Track Ping Times (in milliseconds)
Altitude in meters Ping Time in ms
5 55
The following equation provides an estimate for the time between pings for ranges greater than 3.8m for
the Wayfinder:
Ping time (seconds) = RTB(m)*.42e-3+ 30e-3
Where RTB is the Range to Bottom in meters.
System Synchronization
Typically, data from the Wayfinder is fed into a larger user supplied acquisition and control system, which
collects data from other sources as well. In such situations, it is important to have all the data accurately
referenced to a common time base.
The Wayfinder data ensembles contain a time stamp with a 10 ms resolution from a reading of the real-
time clock before the ping, but the resolution in setting the time is limited to 1 second. If higher accuracy
is required, it is recommended to send the time set command using binary command or the python driver
at or near the full second.
Software Integration
The Wayfinder Tools software provides a graphical user interface for use with a Wayfinder DVL. It is a Py-
thon-based application, so it runs on a variety of operating systems including Windows and Linux and can
be executed directly on the platform.
To facilitate vehicle integration, there is an interface driver also in Python. This driver integrates directly
with many vehicles or top-side computer systems and provides the tools to configure and extract data
from the Wayfinder DVL.
Integration Steps
:
1. Ensure remote access to host computer and internet access.
2. Install Python 3.6 (or later) on the host computer.
3. Install pyserial and numpy via pip for Python 3 on the host computer.
4. Use the WayFinder Python API to access the streamed data or send commands.
Notes:
•
Confidence value for Wayfinder data is not available from the Python API
•
Data timestamp can be up to 1 second off (see
Setting the Wayfinder’s Real-Time Clock
)