Set up the PC computer

PC Hardware

Windows Operating System

PC Hardware

Bathyswath operates with a Windows compatible PC. The PC provides the operator interface and controls. See here for the recommended PC specification and information on installing the software. Laptop computers can be used.

Data archiving

A large hard disk can contain many days’ survey data. However, any disk fills eventually, and so the data needs to be stored for archive. External USB disks, sold for backing-up computer data, can be very useful for this purpose.

Serial interface

This is a standard RS232 interface. It is used to communicate with auxiliary sub-systems such as the attitude sensor, compass and positioning system. Most modern PCs areno longer fitted with serial interfaces, so a way of connecting serial ports to the PC is needed. Ethernet-to-serial converter units have been used successfully for this, for example those made by ‘Moxa’. Some serial interface devices can cause large and un-defined time delays to the input data stream; these should be avoided. One useful tip is to disable any internal data buffering in the device.

There are two connector types commonly used for RS232. These are 9-pin D-type and 25-pin D-type. The 9-pin types are far more common for interconnection between marine systems, and so these are the preferred type. If the sonar system is to be used on a range of installations and vessels, it is a good idea to obtain a stock of serial converter connectors and cables. These provide ‘null-modem’ swaps (swapping over transmit and receive), gender swaps (from pins to sockets and vice-versa), and pin-number swaps (9 to 25).

The pin use on the PC 9-way D-type connectors is as follows. This same arrangement is used on most peripheral devices. In order to connect between these ports, a ‘null modem’ cable is required. This connects pin 2 on one connector to 3 on the other, and vice-versa. Pin 5 is carried straight through.




Receive (into the device)


Transmit (out of the device)




Some auxiliary systems, such as attitude sensors and positioning systems, only output data, and do not require an input. Therefore, only pins 2 and 5 are used. However, some such systems are configured by a program that is run on the PC, so the output line is also used.

The connectors on the PC and auxiliary devices are usually male, that is they have pins rather than sockets.

If more than one system requires data from an auxiliary system, the output can be spliced to both units, but only on the transmit line from the auxiliary system. Do not splice to inputs into the auxiliary device, otherwise the equipment could be damaged.

The use of opto-isolated inputs, either as a feature of the interface card, or as an in-line module, is recommended in order to minimise noise and damage from over-voltage conditions.

Attitude system Ethernet interface

Some attitude and position systems provide data over an Ethernet interface. See here for details of configuring this interface.

Recommended PC Computer Specification




Operating System

Windows XP, Windows Vista,

Windows 7

Bathyswath is compatible with Windows 7 64bit, though generic  ‘USB Serial Converter’ signed device drivers must be used.


Processor P4 3GHz or better

We recommend at least this processor power. The system operates more slowly on lower-powered PCs.


3D accelerated graphics card, at least 256Mb memory

Must support OpenGL functionality


17” or larger

It is possible to open several display windows simultaneously, so a large screen is advisable.


2Gb or more

The more the better, particularly for post-processing. Windows Vista needs at least 1Gb memory.

Hard Drive

100Gb or more

The system uses about 0.5Gb per hour, so plenty of disk space is required for storage and processing. An external USB disk drive is a practical alternative to a large internal disk drive.

DVD/CD drive

Read and write DVD and CD format disks.

Used for archiving data and for installing software. Again, an external USB disk drive can perform this function.

Network card

Standard RJ45 Ethernet

For interfacing to other systems. Some attitude systems provide data on Ethernet.

Serial ports

6-off RS232 ports or more

For input of auxiliary data. Caution is required with plug-in units, e.g. USB; these can sometimes have an unacceptable delay between a message arriving and it being presented to software.

USB ports

4-off USB ports required; at least 6 are recommended

2 for TEMs, 2 free.

More needed if the system uses them itself, e.g. for mouse or DVD drive. External USB disk drives and USB ‘memory sticks’ require more ports.


Wheel mouse

A mouse with a wheel is essential for some of the swath controls, such as zooming and scrolling.


Windows compatible


Windows Operating System

This page provides tips for configuring Windows PCs to get the best performance from Bathyswath. PC computers and operating system versions and configurations vary enormously, so not all of these tips will be appropriate for every situation.

Many of the comments below have been found useful on older computers. Modern PCs, even laptops, usually work well with the Bathyswath software with no modification.

Windows Versions

Bathyswath software is currently tested to run on Windows 7. It should work with Vista and XP. It has not yet been tested with Windows 8.

Windows security settings

Microsoft Windows is ever more security conscious. This is important for preventing viruses and other ‘malware’ from infecting computer systems, but it can prevent Bathyswath from working well and interacting with other computer systems.

The ‘User Access Control’ setting can prevent some actions, for example, the option of setting the PC time from GPS messages in the Swath program. It may therefore be necessary to disable this option in Windows.

For networking, e.g. connecting to Ethernet attitude systems, check the Windows Firewall settings.

Even for stand-alone survey laptops, the use of a good-quality virus checker and firewall is highly recommended.

Windows performance settings

Windows performance can be maximised by selecting ‘Settings > Control Panel > System > Advanced > Settings > Adjust for best performance’.


On PC systems that provide the ‘Hyperthreading’ feature, it is recommended that it is disabled. Use ‘Drivers > Computer’. Set the computer driver to ACPI (it defaults to ACPI multiprocessor).

The Swath processor is a highly threaded application (a thread is a semi-autonomous ‘sub-program’ running inside the main application). The relative operating priorities of the threads are carefully selected and balanced in Swath; Hyperthreading appears to disable this prioritisation.

Multi-core processors

Some users have found that Swath seems to run slowly on dual processor machines. Better performance can sometimes be obtained by setting the processor affinity to just one core. Either:

  • In swathprocconfig.txt, set ‘PCHardware   setSingleProcAffinity     2’. (If zero, Swath uses all cores. If 1, it uses core 1. 2 > use core 2.
  • Find Swath in the Task Manager, right-click, select ‘Set Affinity’ and un-click one of the cores,
  • Or use a tool that sets this automatically when a program runs. Such tools are available as freeware downloads from the Web.

Windows Time Service

The Windows Time Service helps to keep the PC time synchronised across a network. However, it can sometimes make system timing considerably worse, particularly on stand-alone systems. It is therefore recommended that this service is disabled on survey computers, unless it is specifically required. It can be accessed using ‘Start > Settings > Control Panel > Administrative Tools > Services’, and then scrolling down to ‘Windows Time’.

Screen savers and power-off modes

For survey use, disable screen savers and power-off modes.

Display resolution

A high screen resolution is recommended: at least 1280x1024.

USB hubs

Bathyswath TIUs are fitted with an internal USB hub to connect its TEMs to the computer, so a single USB port is provided,

When working with older SWATHplus TIUs, USB TEMs can be connected to the PC using a USB hub. For some systems, better performance can be obtained by connecting the two (or more) TEMs to the PC using a good-quality USB 2.0 hub, (usually with an external power supply). This performance can be assessed by opening Swath, setting the Ping Range to a short range (say 5m), and checking the ping rate in the bottom right-hand corner of the Swath window.