User manual GARMIN GPS GUIDE FOR BEGINNERS

[. . . ] GPS GUIDE for beginners © 2000 GARMIN Corporation GARMIN International, Inc. Unit 5, The Quadrangle, Abbey Park Industrial Estate, Romsey, SO51 9AQ, U. K. Except as expressly provided herein, no part of this guide may be reproduced, copied, transmitted, disseminated, downloaded or stored in any storage medium, for any purpose without prior written consent of GARMIN Corporation. GARMIN Corporation hereby grants permission to download a single copy of this guide onto a hard drive or other electronic storage medium to be viewed for personal use, provided that such electronic or printed copy of this guide contains the complete text of this copyright notice and provided further that any unauthorized commercial distribution of this guide is strictly prohibited. [. . . ] · Signal multi-path -- Occurs when the GPS signal is reflected off objects such as tall buildings or large rock surfaces before it reaches the receiver. · Receiver clock errors -- Since it is not practical to have an atomic clock in your GPS receiver, the built-in clock can have very slight timing errors. · Orbital errors -- Also known as "ephemeris errors", these are inaccuracies of the satellite's reported location. · Number of satellites visible -- The more satellites the receiver can "see", the better the accuracy. Buildings, terrain, electronic interference, or sometimes even dense foliage can block signal reception, causing position errors or possibly no position reading at all. GPS units will not work indoors (typically), underwater, or underground. Multipath Error Blocked Signal 9 · Satellite geometry/shading -- This refers to the relative position of the satellites at any given time. Ideal satellite geometry exists when the satellites are located at wide angles relative to each other. Poor geometry results when the satellites are located in a line or in a tight grouping. military's intentional degradation of the signal is known as "Selective Availability" (SA) and is intended to prevent military adversaries from using the highly accurate GPS signals. This means you can expect typical GPS accuracies in the range of 6-12 meters (about 20-40 feet). However, accuracy can be improved by combining the GPS receiver with a Differential GPS (or DGPS) receiver, which can operate from several possible sources to help reduce some of the sources of errors described above. The next section explains DGPS and how it works. DGPS-How Does it Work? Differential GPS works by placing a GPS receiver (called a reference station) at a known location. Since the reference station knows its exact location, it can determine the errors in the satellite signals. It does this by measuring the ranges to each satellite using the signals received and comparing these measured ranges to the actual ranges calculated from its known position. The difference between the measured and calculated range G PS SI GN AL GPS NAL SIG C GPS RECEIVER STATION AND DGPS TRANSMITTER O R R DA EC TA TI DGPS O N (CORR ECTIO N ) SIGN AL SHIPBOARD GPS AND DGPS RECEIVERS 10 for each satellite in view becomes a "differential correction". The differential corrections for each tracked satellite are formatted into a correction message and transmitted to DGPS receivers. These differential corrections are then applied to the GPS receiver's calculations, removing many of the common errors and improving accuracy. The level of accuracy obtained is a function of the GPS receiver and the similarity of its "environment" to that of the reference station, especially its proximity to the station. The reference station receiver determines the error components and provides corrections to the GPS receiver in real time. Corrections can be transmitted over FM radio frequencies, by satellite, or by beacon transmitters maintained by the U. S. Typical DGPS accuracy is 1-5 meters (about 3-16 feet). WAAS When we fly, there is one thing we all desire: SAFETY (and more legroom!) Exceptional positioning information is the key to flight safety. In deteriorating weather conditions, when visual navigation is difficult or not possible, we need the best position accuracy possible. [. . . ] An external antenna will allow you to use your GPS in an area where a clear view of the sky may not always be possible. External Power Source -- Even with the long battery life you get on most GARMIN products, it's always nice to save on batteries by using a cigarette lighter adapter or AC power source!Mounts -- When you need your hands free, a mount for your GPS can be useful. Many units come with a mount, and several additional mounts are available for other products in our line. [. . . ]