Garmin Depth Finder - Image Location - How far?

[Bassn7]

Just got a Garmin 73 CV. Since all images are showing what has already been passed over, at 3mph how far behind the boat is the item I see? I want to use my new unit with precision for deep brush piles and objects. Thoughts and help anyone...

 

[GA_Boater]

Zero feet. You're seeing what's in the cone, the return is virtually instantaneous and the target is the last thing painted on the screen.

How far back the target is depends on how fast you stop the boat.

 

[Old Ironmaker]

The new units are pretty well instantaneous as GA stated. In the older units you are seeing the history. What you see is dependent on depth of water, cone setting and what KHZ you select to name only a few. A few Bait and Tackle and electronic retailers have classes on the brands of units they sell. The best think I can advise new Golfers to do is take a lessons, that goes for Sonar as well. I drive 90 minutes when they have Garmin and Humminbird seminars on. There are a few You Tube videos worth watching. It's a steep learning curve. When I see something on the screen I like I push the Waypoint selection, then go back to find it, that's the easiest way to find the spot.

 

[dingbat]

GPS “precision” is plus or minus 10 feet with WAAS support. Without, you're looking at plus or minus almost 30 feet.

To this, you add the offset between the GPS receiver and the transducer. You then have to account for the offset from the center of the transducer to the actual target which varies by transducer (cone angle) and depth.

Keep in mind that you have no idea if the target is off to the left or right of center. With experience, you could run split screen and monitor dual frequencies 50/200 kHz (two different cone angles) to try and narrow down the offset.

Hitting Screen history is pretty useless except to get you back to a general area. Depending on your picture advance setting, boat speed, cone angle of the transducer, etc. what is displayed on the screen could be anywhere from 10-200+ feet behind you.

You could use A-Scope mode to home in on the target but you still have to contend with the unknowns listed above.

GPS precision will also be a problem but I don't know how Quickdraw deals with the offset from transducer to GPS receiver thou. Something to try...

Realistically, the best you could hope for is to get within a boat length of your target.