Garmin GPSMap 498 Owner's Manual - Page 80
Using Sonar, Understanding Sonar, Using Dual Frequency, Using Dual Beam - mount
UPC - 753759052171
View all Garmin GPSMap 498 manuals
Add to My Manuals
Save this manual to your list of manuals |
Page 80 highlights
USING SONAR > SONAR PAGE USING SONAR This section covers the additional sonar options for the GPSMAP 398/498 when used with a transducer and the GPSMAP 392/492 when used with a GSD 22, GSD 21, GSD 20 and tranducer. Read the Installation Instructions to properly install the GSD 22, GSD 21, or GSD 20 and transducer. NOTE: You MUST have a transducer installed and connected to your GPSMAP 398/498 to use the sonar features. NOTE: You MUST have a GSD 22, GSD 21, or GSD 20 and a transducer installed and connected to your GPSMAP 392/492 to use the sonar features. Ultrascroll is not available with the GSD 20. Understanding Sonar The transducer mounted on your vessel sends sound waves down into the water in a cone shape, similar to a flashlight beam (covering a smaller circular area at the top and angling out to a larger circular area at the bottom). These sound waves reflect off of any object that they hit, and then the waves travel back up to the transducer. These objects could be fish, branches, the bottom, or any other object that has a density that is different from the water. The transducer receives the sound wave information and then sends the information to the GSD 22, GSD 21, GSD 20 sounder module 72 and then to the GPSMAP 392/398/492/498. The GPSMAP 392/398/492/498 displays the information on the screen for you to see and interpret. The type of transducer and the settings that you choose determine how the information is displayed on the screen. Using Dual Frequency Dual frequency works best for deep water (off-shore) applications. The 200 kHz frequency allows you access to great detail about what is underneath your boat. The 50 kHz frequency provides less detailed information, but penetrates to greater depths with the same power. You can choose either or both frequencies to get the information that you want. If you choose dual frequency, the transducer alternates between the 50 kHz and 200 kHz signals. This capability allows you to see the best picture available at any depth. Using Dual Beam Dual beam works best for shallow water (for example, inland) applications. A dual beam transducer can transmit a narrow or a wide beam. The water area covered by the transmitted sound waves is determined by the beam width of the transducer and the water depth. The narrow beam provides crisp detail of what is under your boat, and is very helpful if you are fishing in deeper water where the beam covers more area (for example, at a 30-foot depth, the narrow beam covers the area of about a 7-foot circle). GPSMAP 392/398/492/498 Owner's Manual