Garmin GPSMAP 178C Owner's Manual

Also see for GPSMAP 178C: Specifications Flush Mount Template Manual Owner's manual

Contents

Garmin GPSMAP 178C Owner's Manual Manual pdf 122 page image

112Appendix GTransducer CoverageTransducer CoverageThe area covered by the transmitted sound waves is determined by the cone angle of the trans-ducer and the water depth. Cone angles may vary between different types of transducers. For example,a 50kHz frequency may provide a “wide” 40° cone angle, with a coverage width that is approximately2/3 of the water depth. As shown in the sidebar, the 40° cone angle (50kHz frequency) approximatelycovers the area of a 20 foot diameter circle at a 30 foot depth. A 200kHz frequency may provide a“narrow” 10° cone angle, with a coverage width that is approximately 2/10 of the water depth. Asshown, the 10° cone angle (200kHz frequency) approximately covers the area of a 6 foot diametercircle at a 30 foot depth.When using the GPSMAP 178C in ‘Dual’ frequency mode, the unit transmits both 50kHz and200kHz signals at the same time. The ‘Dual’ frequency capability of the GPSMAP 178C allows youto have a large coverage area and still retain good bottom resolution. When in ‘Dual’ frequency modethe unit uses the narrow cone angle (200kHz) to display detailed bottom information, keeping “DeadZones” to a minimum, and the wide cone angle (50kHz) for the large coverage area.Fish returns from the wide and narrow beams appears differently on the display. The wide beamtends to show longer fish returns than the narrow beam.Wide Cone Angle Narrow Cone Angle200kHz - 10˚ Cone Angle72" coverage at 30'50kHz - 40˚ Cone Angle20' coverage at 30'