Yet a new breed of system based on the personal computer has evolved in the last decade that is flexible, feature rich and often far cheaper than the boxes set in the dashboard. A standard laptop fitted with navigation software and a database of charts can replicate features found only on the most expensive in-dash units, and it can make navigation far easier. It may not replace your chart plotter, but it can be a powerful augmentation.

The obvious advantage of a laptop-based system is you can, quite literally, take it anywhere. You have the ultimate in portability, bringing your charts with you from helm to saloon to home. We even bring our laptop from boat to boat for delivery work or trading waypoints with fellow captains and cruisers.

Another primary advantage is that a computer-based system can make planning far easier. You can locate marinas, set waypoints, pre-build navigation routes and annotate your charts in a comfortable environment. Most computer screens are larger and have better resolution and color than their in-dash cousins. Most navigation software has the familiar click-through environment we are used to on the Internet. And you have the added benefit of a familiar keyboard and mouse. The result is that you are apt to spend more time navigating, and therefore be better prepared on departure day.

It is also easier to maintain navigation information because data entry can be easier. Laptop charting lets you visually select waypoint locations using your cursor instead of typing latitude and longitude numbers, an error-ridden process even for the most meticulous typist.

Many laptop-based systems have features that cannot be found on hard-wired installations, such as a ship's log, fuel calculator, maintenance schedule and vessel inventory. Add an Internet connection and real-time reports on weather and tides become available. Tie the computer into your boat's instrumentation and you can see the depth in your current location and track your true course. Medium-priced navigation software gives you the ability to call up aerial or satellite pictures and more expensive packages offer bathymetric charts, which show the topography of the sea floor.

Perhaps the most appealing aspect of a computer-based system is that it is flexible, with a wide range of options for boaters with different skills and budgets. Using a laptop you already have, a free software application and a set of free charts, you can setup a basic system at virtually no cost. You can also spend thousands of dollars on a dedicated machine, spend another thousand on software and rig a network to replace your boat's primary navigation system.

And there is much in between.

BUILDING A SYSTEM

All computer-based navigation systems have four main components: a personal computer (laptop or desktop), external sensors such as a GPS, a database of charts and navigation software to read them.

Many boaters agonize over the laptop, but this is probably unnecessary. If you have a fairly recent machine, it may do just fine. If you plan to buy one, the attributes you look for in a good family computer, speed and storage, will apply here as well. There are companies that sell "hardened" or "marinized" computers, but they are generally not necessary. A machine purchased from any number of brand-name vendors will work just fine.

Any computer, PC or Macintosh, that can run graphic-intensive games or handle large photos can display and manipulate large charts. Just remember that the screens are not easily viewed in daylight, and the machines are not waterproof. A reasonable setup would include at least one gigabyte of RAM (two gigabytes is better), an 80 gigabyte hard drive, a high-end graphics card, a screen that is 15 inches or larger and a DVD-drive. Because chart compilations are extremely large, more vendors are producing single DVDs rather than CD-sets and a DVD drive is highly recommended.

Also in the hardware department are external sensors, which link data from your boat to your laptop. There is all kinds of "Star Wars" potential here, including external sensors for sonar, radar and even video cameras to monitor your engine from the helm. But the most common application is a GPS sensor that costs about $100, connects to your laptop through its USB port and can display your boat's position as an icon moving over a chart.