Garmin Fishfinder 100 Owner's Manual

Also see for Fishfinder 100: Specifications Owner's manual

Garmin Fishfinder 100 Owner's Manual Manual pdf 36 page image

28Unit Operation112233On the WaterUnderstanding SonarIf you are familiar with sonar, and can determine what is on the chart,this section may not be for you. This section is intended to help the noviceuser gain some understanding of how the Fishfinder 100 operates and howit can help improve their fishing productivity.To understand what the unit is displaying, it is important to have ageneral knowledge of how the unit works and how it determines what todisplay. Briefly described, the unit operates by transmitting sound wavestoward the bottom of a lake, stream or seabed in a cone shaped pattern.When a transmitted soundwave strikes an underwater object such as thebottom, a piece of structure, or a fish, sound is reflected back to thetransducer. The transducer collects the reflected sound waves and sends thedata to the unit to be processed and displayed on the chart. The underwa-ter data is displayed on the chart in the order that it is returned: firstreturned—first on the chart. The diagram in the sidebar demonstrates thisshowing an underwater scene as it would be displayed on the chart.Generally speaking, if the only thing between the transducer and thebottom is water, the first strong return will come from the bottom directlybelow the transducer. The first strong return sets the bottom level. Weakersecondary returns provide the detailed data. Stronger returns will displayin darker colors, black being the strongest return. In Example 2 (page 30)you can see that the branches and the fish were the strongest secondaryreturns and are indicated in black on the display.That is brief description of how your Fishfinder operates. Let’s take alook at how this data can help you to improve your fishing.Unit Operation and the ChartThis fish is currently in a Dead Zone and is not detectedby the sonar. The fish is in the coverage area of thetransducer, but remember the first strong return sets thebottom level. The fish will eventually be detected whenthe first strong return sets the bottom level below thefish.