The world's waterways arre being revolutionized by GPS. Navigating oceans, bays, rivers, streams and lakes is more precise than ever.From hardworking fishing boats to recreational boaters,  everyone is taking advantage of GPS technology.

The selection and variation of GPS units continues to grow. Handhelds, fixed-mounts, chartplotters, and combination GPS unts with fishfinders add to the selelction. Coupled with other technologies - computers, route planning software, digital charts on CD-ROM and cartridges - there seems to be no end to the conveniences GPS brings to boating.

What is GPS?

The global positioning system (GPS) is a satellite-based navigation system consisting of a network of 24 orbiting satellites that are 11,000 nautical miles in space and in six different orbital paths. The satellites are constantly moving, making two complete orbits around the earth in just under 24 hours.

Selective Availability

One of the biggest benefits over previous land-based navigation systems is that GPS works in all weather conditions. Selective Availability (SA) used to degrade the accuracy of GPS - an intentionally imposed degradation in the accuracy of civilian GPS by the U.S. Department of Defense - but as of May 1, 2007 it was turned off, dramatically increasing the accuracy of even the smallest of units. Be advised that SA is subject to being turned on in the event of defense security situations.

Differential GPS

A typical civilian GPS receiver's accuracy can be improved to 15' or better through DGPS. DGPS employs a second receiver to compute corrections to the GPS satellite measurements. The USCG and U.S. Army Corps of Engineers transmit DGPS corrections through marine beacon stations. These beacons operate in the 283.5-325.0 kHz frequency range, and are free of charge. Your only cost to use this service is the purchase of a DGPS beacon receiver.

Wide Area Augmentation System (WAAS)

Like DGPS, WAAS corrects inaccuracies in readings and substantially improves GPS performance. By replacing the land-based 300kHz transmitting stations with two geo-stationary satellites, wider coverage is possible. These satellites transmit at a higher frequency, eliminating much of the interference caused by weather and stray electrical fields. And since the signals can be transmitted over the same wavelength as standard GPS, a separate differential receiver is not needed. A WAAS GPS receiver is similarly priced as standard GPS units making them quite affordable.

GPS Styles Available

There are many variations on the standard GPS as mentioned before. Models are either handheld or fixed-mount, some have plotting and/or mapping capabilities, and some are combined with depth sounders, fishfinders, and even fuel flow gauges!

Basic Handheld GPS

These units are small, lightweight, and portable, so you can take them virtually anywhere. They operate either on Alkaline or NiCad batteries with an average battery life of 12-24 hours of constant use. Most have 12-parallel channel receivers which lock onto satellites quickly and stay locked on in dense cover. Simple keystroke commands ease use and many are just as sophisticated as their fixed-mount counterparts. The built-in displays are usually LCD, for low power consumption, and can be either alphanumeric or graphical. Backlighting makes the displays easy to read both in bright- and low-light conditions. Some units accept an external antenna for better satellite reception.

Handheld GPS with Programmable Memory

In addition to the location and plotting function of the basic handheld GPS, many units are available on the market that can provide significantly more data for the user. Advanced units today use programmable internal memory that can accept information downloaded from your computer to a CD. In addition to detailed marine cartography, street level mapping, topographic maps, hot fishing spots, and general use points of interest information such as restaurants, addresses, phone numbers, etc. are available. The amount if information  (the size of the chart area as an example) is dictated by the amount of memory storage capacity the unit contains. Not surprisingly, the more memory the unit has, the more the unit costs. Some handhelds on the drawing board will be designed to use external memory chips that can be programmed by the factory with information or the end user can purchase the equipment required to program these memory chips using their computer. This option is currently available for many of the fixed-mount chartplotters on the market.

Fixed-Mount GPS

These bring the convenience of the handheld to a unit that you can permanently mount anywhere on your boat. The fixed-mount units generally offer larger, more visible screens, more options, and better position fixing than the handheld units. Most units are water-resistant and can withstand a certain amount of water sprayed on them without damage. Some offer internal antennas for easier mounting options and others offer external antennas for clearer antenna line of sight to the satellites.

Chartplotters

Many chartplotters accept digital cartography in the form of pre-programmed memory cartridges. Complimenting the included basemap by significantly increasing detail. Navionics, C-MAP, and Garmin BlueCHarts, provide limited worldwide coverage and detailed local maps. With databases of navigation  markers, depth contours, and more. Other units with internal memories use the same information downloaded from a CD-ROM.

Land-Based Units

We also carry several hand-held GPS which are great on, and especially off the water. These units contain specialized databases of North and South American roadways and general landmarks. Many basemaps include state and country boundaries, lakes, rivers, streams, airports, cities, towns, coastlines, and U.S. state, and interstate highways. All units also accept more detailed road and landmark information from specialized digital cartridges. CDs are also compatible with personal computers.

Garmin Land-Based GPS

Garmin carries a line of data cards and CDs called MapSource™ which are compatible with all of their land-based units. They provide street level mapping detail-even giving you access to business listings and points of interest.

Magellan Land-Based GPS

Magellan's DataSend™ CDs are compatible with all their land-based units, and they contain detailed land and nautical points of interest.

Electronic Charts

Electronic charts are digital replicas of paper charts. They are very convenient because they contain a large number of paper charts, sometimes 50 or more, on one cartridge. You can easily scan through the chart using your GPS or personal computer. Electronic charts are, however, only an aid to navigation. They are designed to facilitate the use of authorized government charts, not to replace them. So please keep your paper charts on board! Only official government charts and Notices to Mariners contain all the information needed for safe navigation. Electronic charts can be helpful when used in combination with official charts. Many GPS units accept electronic chart cartridges which are packed full of navigational information, yet physically smaller than a credit card.

Micro-Charts

Micro-charts are even smaller versions with the same amount or more information available. Not all units are equipped to handle the micro-charts, however. There are three basic types of electronic charts, G-Charts, C-MAP, and Navionics.

Garmin G-Charts

There are two types of G-Charts offered by Garmin for use with their products, Inland and Offshore. Inland G-Charts cover lakes and reservoirs within the United States, and include icons indicating boat ramps, marinas, dams, and other items of interest. Offshore G-Charts, utilizing Navionics cartography, can include six different types of charts: Coastal, Detailed, Fishing, General, Extra-Detailed, and Port Services. They provide coverage of offshore waters, bays, and the Intracoastal Waterway. Coverage includes the Pacific Northwest and Alaska, the Pacific Southwest, the Great Lakes region, the Northeast/Mid-Atlantic, and the Southeast/ Caribbean, as well as Central and South America, Australia/New Zealand, Northern Europe/United Kingdom, Western Europe, the Mediterranean, the Far East, and Southeast Asia.

C-MAP Electronic Charts

C-MAP offers several versions of electronic charts, including C-MAP NT, a professional database now available in the marine market. It is derived from CM-93®, C-MAP's SOLAS class database designed according to the principles of the International Hydrographic Organization standards on electronic charts. The cartridges offer more chart information and smoother, faster panning and zooming. You can choose the amount of detail you want through zoom and you can customize your own charts.

C-Map NT with Tide Info™ and Port Info™ displays real time tidal predictions, past, present, and future as well as complete and up to date information on port services anywhere. You can search for the nearest sites or see what facilities are available at any given port quickly and easily.

Navionics Electronic Charts

Navionics designs, manufactures, and markets marine electronics charts for commercial, recreational, and government markets around the world. Navionics, winner of the 1996, 1997, and 1998 NMEA Award for Best Electronics Charts, owns a large marine electronic chart database consisting of over 15,000 nautical charts. They are available in hundreds of Navionics chart cartridges, with up to 200 nautical charts and port plans in one 32MB cartridge. Navionics charts are available in credit-card size memory cards called Microcharts™ and the postage-stamp size Nav-Chart™.

How to Pick Charts

Most charting system manufacturers offer a "from/to" base map where you can simply identify the areas where you will be boating. For more detailed information you will then need to find the corresponding G-Chart, Navionics, or C-MAP chart number for your area. The type of chart you choose depends on the type of unit you have. You can then call BoatUS or visit one of our Marine Centers to purchase your chart.

Electronic Charting Software on CD-ROM

These software packages help you to quickly, easily, and accurately plan and map out your trips on your home PC. The information can then be downloaded into your GPS. Route planning software packages work with digital charts made from paper charts like the ones discussed previously, but these charts can be modified for your own personal use. You can label waypoints, rotate and overlay charts, calculate distance and bearing to targets, save all your fishing spots, measure distances between land formations, and more. These systems give you an instant visual image of your location and allow you to scroll through a moving map. We carry several of these software programs and their compatible digital charts.

Inside GPS-Basic Features vs. Key Upgrades

In the Annual Equipment Catalog, we have outlined the basic features and key upgrades of all types of GPS. This information is intended to help you choose the GPS that's right for you. The basic features we list are those you'd expect to find and that are necessary for application in the marine environment. The key upgrades are features that personalize the unit. For example, we list color screens and Tide charts as key upgrades. A color screen may be nice for viewing across the cockpit, but not necessary for everybody. Tide charts would also be helpful in some applications, but not all.

Basic Features

The basic features that most GPS share are water resistance, backlit displays, 12-channel receivers, differential readiness, and external antenna capability.

Water Resistance: Absolutely necessary for GPS use on the water. Sprays entering the boat as you're cruising, or an accidental dunk are no problem for most of the GPS units we carry. See individual write-ups for clarification.

Backlit Displays: Make it much easier to read all the information yon the screen. From low-light to bright-light, you'll appreciate this feature.

12-Channel Receivers: Constantly search the sky for 12 satellites and are capable of locking onto all 12, contributing to excellent "viewing" even in dense cover.

Differential Ready: Important if you would like to purchase a differential beacon receiver later on to improve your GPS accuracy to 15' or better.

External Antennas: Contribute to better "viewing" of satellites for improved accuracy and lock-on tracking.

Key Upgrades

The key upgrades we list are differential built-in, upload/download capability, extra-large screen, color screen, built-in database of landmarks, tide chart capable, remote antenna included, accepts software cartridges or CD downloads.

Differential Built-In: Is an excellent feature if you are concerned about improving your GPS accuracy over the error caused by Selective Availability.

Upload/Download Capability: Good for those who like to plan routes at home on a personal computer and download them into the GPS. You can then make modifications on the information in the GPS, marking new fishing spots etc., and upload that back to your computer.

Extra-Large Screen: Good for larger boats where viewing information across the cockpit is necessary. Also helpful if the GPS is interfaced with several other instruments, and all the information is detailed in smaller windows on one screen.

Built-In Database of Landmarks: Helpful on land-based units by adding greater detail to the built-in basemap.

Tide Chart Capable: Helpful when you need information on the tides quickly and at your fingertips.

Remote Antenna Included: Important for improved accuracy and "viewing" of satellites. Accepts Cartridges/CD Downloads: Necessary for detailed chart information and planning and plotting routes.

Current Loran Status

The federally operated Loran navigation system has been saved from a premature shutdown and may be operated by the federal government until 2008. The decision follows a high level meeting of the Department of Transportation, the Federal Aviation Administration, and U.S. Coast Guard officials.

Operated by the USCG since the 1970s, Loran was targeted in 1994 for a shutdown as early as 2007 due to budget concerns, rather than remain operational until 2015 as planned. With over a million civilian users, most of them mariners, the prospect of Loran's early demise created a furor among navigators who had hundreds of million of dollars of Loran equipment invested in their boats. BoatU.S. immediately launched a grassroots campaign to save Loran and has worked with members of Congress to secure funding for Loran.

Loran and GPS are not competitors, but are systems with different strengths and weaknesses, as well as different failure modes, so that they complement each other well. The deliberate signal degradation through Selective Availability (slated to be eliminated by 2006 or earlier) is a pitfall of GPS receivers. Selective Availability does not affect Loran. Loran coverage by U.S. ground stations extends from Russia to the Caribbean and includes much of Canada. The system is worth keeping as a complement and back-up to GPS receivers.