Break out the silica gel and tie down your laptop. This week evolution is all at sea with the latest in software for the computer-friendly boat owner.

Computers are capable of handling almost all navigational functions aboard a small boat and the choice of suitable software is growing larger with successive boat shows.

Electronic charts are growing in popularity against the paper version because they can be updated in seconds via the internet.

GPS (Global Positioning System) allows pinpoint accuracy even when you can't see a fathom in front of your nose.

Laptop design is also far more rugged than ever before. Some recent models are even guaranteed to be water and shock-proof.

PC Maritime of Plymouth has developed its excellent Navmaster 4.2 package (at around £399).

This really is the ultimate computerised navigation product and allows a user to link a GPS receiver to their computer and plot their course using electronic charts.

ARCS (Admiralty Raster Charts Service) electronic charts are available on CD-ROM.

They are supplied by the United Kingdom Hydrographic Office in Taunton, which has released its Skipper Folios covering the whole UK coastline and popular sailing areas around the world.

Almost 3,000 charts are currently available as ARCS files and look just like on-screen versions of the more common paper charts.

Anyone who has not used electronic charts before may be concerned they will not get the same quality image as that found on a paper-based chart but those doubts would be unfounded.

Raster charts are simply scanned images of the original Admiralty product and carry the same guarantee of reliability.

Having installed the basic navigation software package and ARCS charts, the new user needs to link a GPS (a suitable unit costs around £200) directly to the serial port of their computer.

Within a few minutes it is possible to get an accurate position on the chart transferred directly from satellite to computer.

Prospective users will be delighted to know the GPS service is absolutely free and uses transmissions from satellites buzzing round the earth to gather their positioning data.

Finding your geographical position is very important but the trouble with being out at sea is there are very few signposts to tell you where to go next.

Nowadays, electronic navigators use virtual signposts called waypoints to find their way around the oceans.

Essentially a waypoint is a geographical position, entered as latitude and longitude, which serves as a target point.

The GPS is able to plot with incredible accuracy the boat's true position and will tell the navigator the direction to steer in order to reach a chosen target.

Unfortunately, the GPS doesn't take into consideration the tides and currents that can push the boat off course and it certainly doesn't spot hazards such as rocks and wrecks that may be on the chosen route.

This is where the navigation software comes into play.

Using electronic charts to find the 'nasties', the digital navigator can create a virtual electronic course that avoids all the hazards.

Although electronic navigation systems should only ever be used as a back-up to more conventional paper-based chart-work, they can help any navigator to hone their skills and speed up operations.

If the power fails or the notebook computer malfunctions, then always be prepared to switch back to traditional navigation techniques.

Computer-based navigation packages are definitely not a substitute for knowledge and experience.