There have always been reports of the 700 series being a little lacking in processing power ...so it is possible that the mapping on your Zero Line card could be slowing some other processes down ...
Do you notice a difference without the Zero Line Card in the unit ... ??
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Now fish arches ... Unfortunately the Chart speed is global ...meaning the Chart speed is the same for 2d/DI and SI ...
This is an unfortunate conundrum ...because imaging needs a Chart speed to match boat speed ...conversely 2d needs a much faster Chart speed ...
And not to mention that fish arches are elusive anyway ...
Here is fish arch info ...
https://www.google.com/url?q=http://www.humminbird.com/Category/Support/FAQ/FishArches/&sa=U&ved=0ahUKEwjm0N-cruDNAhUDdh4KHURSDEsQFggEMAA&client=internal-uds-cse&usg=AFQjCNE_PXOhZ5qQRIyQ2NUGZH81LcH9pw
Rickie
I am hoping it's a read/write being the roadblock here and not the processing power of the unit. If that's the case then Autochart is of little value to me if I have to shut it off to actually get use out of my fish finder. Brutal.
I got my 798 early 2014 and got the Autochart card mid 2014 and have just noticed the lack of quality of finding fish or with side scan. Going back over my recordings I could see they were really quite good before I began using Autochart and it almost seems to be progressively getting worse, to the point now I only see slivers of strong returns...which is what got me thinking about chart speed being too low. Matching chart speed to boat speed is just making sure you're not overly stretching or compressing what's being scanned. However I'd fall asleep if I had it on 2 when I was trolling at 2mph...although when I crank it up I honestly didn't notice much of a difference. I watch tons of youtube videos of Autochart tutorials and watch them crank up the chart speed and it's noticeable faster, mine isn't like that at all.
It also makes sense with my side scanning as it just looks like featureless garbage now, because if you'r running at a very low chart speed and moving quickly that's what it'd look like. I think Autochart and/or recording is bringing my 798 to it's knees....
I have a feeling my chart speed is running at 1 or 0.5 (even if I crank it up to 10) and if I shut off the maps the chart speed will pick up and then I can start to get good side scanning and 2D sonar. That really sucks if that's the case!