I'm taking it your talking about off your transom mounted transducer, if so when you first see what you want to mark.
I'm sure this has been discussed numerous times but I cant seem to locate a thread that does. My question is. When idling around at 2-3 mph or so and you see fishable structure, when should you toss a marker? When you first see the image enter the screen, middle of the screen etc. I have been trying to mark structure this way due to the slowness of this unit's location update. For example, I tried to go to a saved Waypoint last night and I got close but could never get on it. I just kept going in circles so I gave up and found another spot close by and tossed a marker when I saw structure. I caught fish but no idea how close I actually was to it. Atleast I never got snagged on it.
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BigDawgg LIKED above post
I'm taking it your talking about off your transom mounted transducer, if so when you first see what you want to mark.
It's on the transom. I was just confused, I was reading about cone angles and how it was affected by depth. I just diddnt know if at 30 feet water depth for example, when an image first appears on the screen if was actually in front of you due to the angle or even out to the left or right.
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On a DI unit .... it would be hard to tell if the cover is actually right, left, or dead center. Maybe a little less so, with the 800kHz setting than the 455kHz setting ... just because of the wider angle of the 455kHz. But, with the fan shaped 3deg thickness of the ping, the cover is going to start showing up on the screen a split second before the transducer gets to it.
Depth matters, as does the kHz setting you're using, because at your 30ft depth scenario ... a 800kHz setting beam is @ 45deg, so your bottom width of the ping is ~28ft wide (14ft to either side of the transducer) & a 455kHz setting beam is 75deg, so the bottom width of the ping is ~45ft wide (22.5ft to either side of the transducer) ... and that cover item that starts showing up on your screen could be anywhere within the 75deg or 45deg width of the sonar beam. And if you're idling along at 2-3mph, you're going to be on or past it by the time it starts showing on your screen.
This is the ping chart I use for my calculations : (And the one I used back when I had my Elite 5DSI unit)
Criss cross over the brush slowly after it has been marked to get the best GPS markings in 2d. When you go over it on the third time and it shows up directly under you then mark it and this will be your best location.
Slabprowler LIKED above post
Here's a good video that may help you with marking spots;
How to Hit Offshore Structure First Cast Every Time! | Offshore Bass Fishing Tips - YouTube