Gemini 720is Imaging Sonar
Document: 0703-SOM-00002, Issue: 7
8
© Tritech International Ltd.
1. Introduction
1.1. General Overview
The Gemini 720is is a 2D imaging sonar. It is a multibeam sonar, offering a 120° field of view
with update rates of up to 30Hz giving rapid feedback to the user (hardware is capable of
30Hz, Seanet Pro is limited to 15Hz).
The system consists of the Gemini sonar head(s) and either Gemini or Seanet Pro control
and display software. The software communicates with the sonar over Ethernet (100Mbit·s
-1
),
or Very high speed Digital Subscriber Line (VDSL) via a VDSL to Ethernet converter.
The software is Windows® based and will run best on a display of resolution 1280x1024 or
greater with 32-bit colour resolution.
1.2. Communications
There are two connection options, 100Mbit·s
-1
Ethernet and VDSL. The sonar will
automatically detect which connection is available and switch to that connection.
The VDSL option allows a single twisted pair to be used for communication to/from the sonar
at high speeds dependent on the length and quality of the cable (see Chapter 2,
Tritech International Ltd
supplied VDSL Adapter Unit takes the
two wire VDSL input and bridges it to Ethernet for simple connection to a PC.
VDSL maximises the data rate by testing the quality of the connection at start up and adapting
the speed accordingly. With VDSL there is a trade off between link speed and noise immunity.
There is a setting in the software that allows optimisation to cope with the level of noise
introduced by other parts of the system.
Note
The red LED on the VDSL adapter box may light up to indicate that the link is
experiencing higher levels of electrical noise. The sonar can cope with some
electrical noise on the link but it may reduce the ping rate.
When using an Ethernet connection it should be noted that the Gemini Sonar can fully utilise
a 100Mbit·s
-1
link while returning the sonar data. If the Gemini Sonar is to share an Ethernet
link with other high bandwidth devices, such as video cameras, it is recommended that the
100Mbit·s
-1
devices share a gigabit (or faster) link to the surface to reduce possible network
congestion.
1.3. Electrical Connection
Depending on the electrical connector fitted to the Gemini not all communication modes may
be available for use. Please refer to Section 3.3, “Sonar Head Pin-Out Diagrams” for details
on the range of connectors available and the appropriate communication modes support.
