TVG setting and side imaging?

[puhlw]

I have never been very happy with the side imaging on my garmin. I have tried setting the range to say 30-50ft to increase the image quality but the picture just always looked way to blown out. I turned the gain down to almost nothing but then it seemed like I couldnt see anything. Yesterday I move the TVG from medium to High, and presto things look awesome.

Bottom of the screen shows medium TVG and top shows High TVG. (not the best image but you get the idea)

My question is on high TVG are there things (details) that I am missing?

[Larry3215]

Next time see if you can capture the screen and save it to the sd card. I cant tell anything from that pic - too much mess from the cell phone image :)

I havent played with TVG much at all. The little I have, I didnt see much improvement, if any, over the default or Auto settings.

[puhlw]

Is there a way to upload larger image files onto BBC? The original was 6.4mb and looks much better but wont upload.

[Riccochet]

Mine is the same way, 7608 w/ GT52. The water column is blown out unless TVG is set to high. But, I feel, I don't get the soft fish returns that I should be getting. No matter the settings. I've played with it so much, just can't see fish like I did on my old HB. 2D sonar is fine, but I like to side scan points for suspended fish that were easily visible via the return and shadow on the HB, not so much on my Garmin.

[puhlw]

This image is a bit better, you can see a clear line where it goes from super bright to more of what you would expect.

[puhlw]

I should probably mention this is a gt30 running through a black box to my 1040xs

[MROBIT294]

I have a Garmin 7SV. I fish shallow waters and also find that for best image quality, I have to have TVG set to HIGH. I read on another thread that TVG is mainly for deeper water, so I am guessing I may be missing fish returns.....

[puhlw]

yeah that is kind of what I was thinking also, though there is a lot thats hidden in the overpowered center section also. Are all those white dots in the upper right portion fish you think? There are some rock piles out that way also I know.

[Larry3215]

TVG = Time Varying Gain. It adjust the Gain to its higher at further distances and lower close in. I can see where it might or might not help much with sideview, but your also going to have to play with contrast and brightness. It could take a lot of playing around to dial it in if the conditions are bad.



tvg.JPG

[Larry3215]

This image is a bit better, you can see a clear line where it goes from super bright to more of what you would expect.

Part of your problem here is you have the range set too far for the depth. If you are looking for fish in the water column, set the range much shorter. Try 2 or 3 to maybe 4 times the depth at most. That will make the water column section much larger and targets will be a lot easier to see. AS you have it, you need the gain way up to see those distant targets, which washes out the close in stuff. TVG might help some, but different basic setting will help more.

[puhlw]

This may have been covered, but how do you mark a waypoint on structure out to the side on side imaging? This is on a 1040xs. I assumed you would just move the keypad/cursor over to the spot and hit mark but that doesnt seem to do anything on mine.

[puhlw]

and I know the gps points will not be exact due to how side imaging works but at 10ft deep and 100ft out they should be reasonably close.

[Larry3215]

You need to look at your manual for the exact details on your mfd, but if you just hit Mark, it always marks the boat position - not the point out to the side. You need to create a New Waypoint.

For my 7610, this is how you do it.



waypoint.JPG

[puhlw]

Well garmins manual is pretty useless but I figured it out from what Larry described.. Go to menu then hit pause, then you can move the cursor over to a spot to mark it.

[TeeDee]

Back to the original point of TVG--from another forum I followed a rec to turn OFF the TVG (didn't even know I had it) for clarity and better display of soft targets on sv. A couple of resources that whose opinions I value suggested that TVG has no real value in most freshwater apps. Mine was set to MED, I turned it OFF and could see nothing but 'snow' in the sv water column and over most of the screen. Tried several basic adjustments and went back to MED. My range was set to 40' and I was in 8-15 fow. Perhaps just for grins I will try Auto range, or even setting it to 3x the depth. Didn't work as suggested for me without TVG.

[puhlw]

Yeah mine is basically just snow out to 50ft unless I go to high TVG or turn the gain down to like 10% manually, but then I get no returns from further out. I guess I will run HIGH TVG until something better comes along.

[Todd Driscoll]

Well garmins manual is pretty useless but I figured it out from what Larry described.. Go to menu then hit pause, then you can move the cursor over to a spot to mark it.

You can just use the arrow pad to pause the sonar, then create a waypoint using the Create Waypoint soft key.

[puhlw]

The arrow pad on my 1040 doesn't seem to pause. Do you need to hold it in or something? That's the way I expected it to work. Like hummingbird does

[Larry3215]

Yeah mine is basically just snow out to 50ft unless I go to high TVG or turn the gain down to like 10% manually, but then I get no returns from further out. I guess I will run HIGH TVG until something better comes along.

You shouldnt be getting all that snow at low brightness (not Gain) settings unless your water is really dirty/weedy, etc. Maybe you have an interference problem or some other setting needs tweeking. Can you post some screen captures - with the SD card - so fine details show up? Maybe we an help dial it in a bit better.

By the way, I often say "Gain" generically, when I shouldnt. You dont adjust Gain on sideview and downview with Garmin. You adjust the Brightness. Gain only applies to traditional 2D sonar. Maybe thats your issue?



gain.JPG

[puhlw]

I think I tried that but not positive. I'll take a look next time I am out.