User manual RAYMARINE RAYSTAR 112 GPS

[. . . ] Distributed by Any reference to Raytheon or RTN in this manual should be interpreted as Raymarine. The names Raytheon and RTN are owned by the Raytheon Company. GPS SENSOR OPERATION MANUAL RAYSTAR 112 Installation and Operation Handbook RAYSTAR 112 GPS SENSOR Owner/Installation Manual PURPOSE This manual contains very important information on the installation, operation, and maintenance of your new equipment. In order to get the best results in operation and performance, please take the time to read this manual thoroughly. IMPORTANT NOTICE This device is only an aid to navigation. Its accuracy can be affected by many factors, including equipment failure or defects, environmental conditions and improper handling or use. [. . . ] The updated information is transmitted to each satellite via the ground antennas, which also transmit and receive satellite control and monitoring signals. The User Segment consists of the receivers, processors, and antennas that allow land, sea, or airborne operators to receive the GPS satellite broadcasts and compute their precise position, velocity and time. The satellites continuously broadcast their navigation messages at a frequency of 1575. 42 Mhz (for civilian use). Superimposed on the navigation message is a high rate coarse acquisition (C/A) code used for precise positioning measurements and positive satellite identification. The C/A ID code permits the user to identify particular satellites and, in some cases, to determine and select the "best satellites" to use in position calculations. If it were possible to measure true satellite ranges directly, it would only be necessary to track data from any two satellites to obtain a vessel's latitude/longitude. In actual practice, for marine navigation, the receiver must lock onto and track a minimum of three satellites in order to resolve timing errors, including the receiver's own internal clock timing bias error which must be factored into the various range calculations. Chapter 1: Introduction 3 Normally the Raystar 112 tracks up to 12 satellites (if visible) and uses all tracked satellites for calculating position fixes. By using these satellites, the processor can determine the amount of clock errors in each range calculation. The receiver subtracts the error bias equally from each range solution until the lines of position (LOP's) intersect. Theoretically, this process can produce highly accurate latitutde/ longitude (L/L) position fixes for navigation within +/- 15m (rms). Continuous tracking of each satellite allows the receiver to perform this timing adjustment process and to calculate accurate measurements to the satellites. This sensor design method provides fast efficient acquisition and accurate position updating, even when satellites are obstructed from view. The US Department of Defense, for security reasons, has included a special mode in the GPS satellite system design which introduces variable timing errors into the satellite signals. This mode is known as "Selective Availability" (SA), and when it is enabled, is designed to provide less accurate fixes for all users (except military users). Accuracy in the order of +/- 100 Meters (rms) 95% of the time is obtained when SA is ON. This means that 95% of the time the actual ship's GPS Lat/ Long position will be within a radius of 100 meters (+/- one football field) and 5% of the time the actual position will be out of this 100 meter circle. Selective Availability has been enabled almost continuously since early 1991. The use of Differential GPS technology can remove most of these intentionally induced errors in the GPS satellite signals due to the "Selective Availiblity" mode including errors that can result due to environmental conditions as the satellite signals travel to earth. When you attach Raytheon's Differential Beacon Receiver to the Raystar 112 GPS sensor, the GPS differential corrections can improve the L/L 4 RAYSTAR 112 Installation and Operation Handbook position output accuracy of the Raystar 112 from +/- 100 meters down to 5 to 8 meters in most cases. The Raystar 112 provides NMEA 0183 formatted data at its output as follows: RMC GLL VTG GGA GSA GSV Combines position, course, and speed Vessel's Latitude/Longitude position Course over the ground, Speed over ground Ships L/L position & satellite status information Active satellites and DOP Satellites in view This data can be supplied to plotters, fishfinders, radars, integrated systems, etc. , which are set up to use these sentences from the NMEA 0183 format. The base of the sensor has a slot cut into it so that the prewired cable can be fed externally of the mount or extension mast if so desired. If the connector is removed, the cable can be fed down through the extension mast or mount, exiting through the mount assembly. The aluminium base of your Raystar 112 Sensor has received a chromation treatment which adds toughness, resistance to wear and tear, and resistance to corrosion of the assembly. Prior to attaching the GPS sensor to the mount, we do recommend that a light coating of the silicon grease be applied th the surface of the threads of the sensor and mount. Screw the antenna onto the mount fully by hand while paying attention to avoid curling, tight loops, and kinking of the cable. When the unit is fully threaded on the mount use a proper sized spanner wrench and protective cloth to grip the base and snug the sensor to the mount. If the cable is fed internally through an extension mast, it is recommended that the cable slot in the sensor base assembly be sealed with RTV silicon sealant as protection from the environment. [. . . ] This will occur as long as the ship remains within approximately 100 NMof the L/L position where the unit was turned OFF. If the vessel has been moved a substantial distance from the last saved position and the GPS sensor is then powered up, the unit may again go through the Cold Start routine. The time to acquire the satellites and get your position can be reduced by re-entering your new L/L position, date, and time information. 3. 2 Geodetic Datum The normal Geodetic datum used by the Raystar 112 sensor is WGS-84. Mariners can/may find considerable errors (up to 200 m) in plotting own ship's position if their charts were created using one type of geodetic 12 RAYSTAR 112 Installation and Operation Handbook data system while the GPS sensor is busy calculating positions using another data system. [. . . ]