Raymarine manual Raynav 300 GPS Plotter Owner’s Handbook, Safety Notices, Prelim Pages

Prelim Pages iii

Raynav 300 GPS Plotter Owner’s Handbook

SAFETY NOTICES

WARNING: NAVIGATION AID

This device is intended to be used as an aid to navigation. Its accuracy can be affected by many factors, including equipment failure or defects, environmental conditions and incorrect handling or use. It is the user’s responsibility to exercise common prudence and navigational judgement. This device should not be relied upon as a substitute for such prudence and judgement.

CAUTION:

Do not connect/disconnect the GPS Antenna from the display unit whilst power is applied. Such action could cause irreparable damage.

WAAS Satellite Differential GPS

WAAS provides differential augmentation to GPS. It was designed to enhance the basic GPS service to satisfy the aviation industry’s navigation requirement for instrument flight rule navigation and landing, IFR and approach landings. WAAS has been in near continuous broadcast since December 1999 and is also available for other GPS applications such as marine navigation, surveying, agriculture and automotive systems.

WAAS consists of a network of ground reference stations across the United States that monitor GPS satellite data. The master stations collect data from the reference stations and create a GPS correction message, taking into account selective availability (SA), GPS satellite orbit and clock drift, and signal delays caused by the atmosphere and ionosphere. The ‘corrected’ differential messages are then broadcast through two Geostationary Earth Orbit (GEO) satellites on the same frequency as the GPS signal. The Raymarine Raynav 300 and 301GPS receiver utilizes one of its 12 channels to ‘listen’ and decode the corrected WAAS messages. The result is a DGPS system that provides improved accuracy (<3 meters) in comparison with standard GPS (100 meters with SA, 15 m without SA) and land based DGPS (10 meters) systems.

The WAAS system is shown diagrammatically in Figure i.