Background
C-MAX Ltd was founded in 1992 and in 1994, we introduced the innovative CM800 sidescan sonar system.
The current CM2 system was introduced in 2002, superseding the CM800. The CM2 built on the success of the CM800 but improved on it in many respects.
The CM2’s tow cable telemetry means that both coax "soft" cables or very long twisted-pair cables can be used. A key point to note is that the CM2 is a true digital system, with the images being digitized in the towfish. There is no loss of image quality in the tow cable, unlike sonars that rely on analog towfish and analog telemetry.
Soon after the introduction of the CM2 its top end electronics changed to the compact Sonar Transceiver Unit (STR). The STR links to a laptop via a USB cable. For a period an all-in-one clamshell unit (the C-Case) option was offered, replaced now by the optional C-Shell waterproof housing for the STR.
In the towfish, the basic configuration was carried over from the CM800 but improved in nearly every respect. The angled shields that protect the transducers from impact were extended to project out further from the towfish, and to wrap around the front, lower profile of the transducers. As well as providing protection these shields serve two other functions. They have a hydrodynamic role in maintaining the pitch stability of the towfish. They also act as acoustic reflectors, primarily for the high frequency beams, cutting down the signal in the upper sidelobes by an average of 20dB. This significantly reduces any interference by surface echoes when working in shallow water.
The CM2 towfish transducers retained our unique configuration that includes an additional pair of depressed short arrays that ensure good coverage directly below the towfish, and also act as an echo sounder to allow the towfish to measure its altitude automatically.
The CM2 towfish also kept the stainless steel construction and the double O-ring sealing design that has ensured that no CM2 or CM800 towfish has ever leaked. The CM2 towfish also keeps the breakaway mechanism that, if an obstruction is hit, causes the towfish to flip and tow from the rear via a safety lanyard. This mechanism has proved so effective that very few towfish have been lost. A handle was added to the CM2 towfish to make one-man launch and retrieve even easier.
Our experience of the CM2’s reliability and our confidence in its design led us to increase the warranty period for most items from 12 months to 36 months.
Development has not stopped. In 2006 a new design of remote-control portable winch was introduced, replacing the SK172 type. This winch features an automatic overload clutch, “soft start” and a temperature alarm amongst other improvements.
A more recent development is the towfish wing depressor, taking advantage of the unique design of the CM2 towfish to put a high-aspect-ratio, efficient wing directly below the tow point. This wing depressor is very effective in reducing the length of tow cable required to get to a particular depth, yet is light enough not to impede launch and recovery.
The range of compatible accessories has been extended to include large and small counting pulleys, a fixture for mounting the towfish on an overside pole, and an attachment for a USBL transponder.
On the software side, a new survey package MaxView was introduced in 2003. Since then MaxView has acquired a number of additional features, some of which are the direct result of customer feedback. It is notable that MaxView is available free-of-charge to any user of the survey data; the only function that requires the purchase of a software license is for the original acquisition of survey data.
The CM2 system is also directly compatible with most leading third-party survey packages.