Small electronics allow for compact nav package

From Ocean Navigator #138
May/June 2004
I have always wanted to have a complete navigation package for use on small voyaging boats and for temporary use on other boats. Putting one together has been a problem due to the weight and bulk of instruments and reference books. However, with the development of small pocket computers and small GPS/plotter receivers, it is now possible to carry a very powerful, multifunction navigation package in one small, light box: a sextant case.

In a search for the most complete and smallest practical navigation package, I have put together two items that fit into a sextant case and provide a combination of both celestial and GPS modes of navigation suitable for either primary or backup navigation. In addition, the computer can be used for many other standard functions of a PC, such as recordkeeping, writing, calculation and communication.

Image Credit: Albert Rentschler photos

The Magellan Nav 6000 is a hand-held mapping GPS using the popular C-Map charting cartridges. Its size is handy in that it can be kept at the helm for constant reference underway, but still has a screen large enough to allow easy viewing on both power and sailing vessels, even in bright sunlight. It can also function as a chronometer for the setting of the navigation watch used for timing celestial sights. A data cable is used to feed NEMA 0183 data from the GPS to the pocket computer; a second cable connects the GPS with a small, remote antenna that amplifies the signal and permits operation belowdecks.

The pocket PC I selected is a Psion Series 5 with a marine navigation software program from Dolphin Maritime Software Ltd. This computer provides all of the normal functions of word processing, spread sheets, address file, calendar, calculator (including scientific functions), alarm and world time information, among others. The major advantage in addition to its small size, is the touch screen with complete keyboard, making data entry much easier and faster than with only the touch screen of most pocket computers. A simple communications program allows for fax and email, using an optional modem or directly by infrared connection to some cell phones. It also contains a voice recorder and separate memory storage on standard compact flash cards. For operation on deck, a waterproof case provides protection from the elements.

The Marine Navigator 5 program is unique in that it allows for keeping a continuous log of positions from DR, GPS and celestial sight fixes, an almanac for sun, moon, Venus, Mars, Jupiter, Saturn and 58 stars, storage of GPS waypoints and routes, an AstroPlan star-finder function for all bodies available at your position for any time (with azimuth and altitude to 0.1 degrees), sight reduction and storage, plotting running fix from sights, times of civil and nautical twilight and sun meridian passage, great circle course and distance from and to any point with selected plane or Mercator sailing.

Image Credit: Albert Rentschler photos

The author’s compact nav package includes a Psion 5 pocket PC, a Magellan Nav 6000 hand-held GPS, a Nautical Almanac, H.O. 211 sight reduction tables, and, of course, a sextant.

The marine navigation program also provides for the logging of position data at specified intervals and automatically stores GPS and celestial fixes. Manual DR entries can be added at any time, and the log can be printed. Data can be stored on the removable compact flash card or downloaded into a PC.

These pocket computers are somewhat fragile and not really intended for operation in a marine environment, so a sextant case is a good place to store them. Also inside the sextant case there is just enough room left for a current almanac and a copy of Ageton’s H.O. 211.

Albert C. Rentschler lives in Lake Geneva, Wis., and sails the Great Lakes on a 64-year-old sloop.

By Ocean Navigator