Carbon 12 depth reading

I just purchased a Carbon 12 and am using C-Map Discover Chart chip. I was wondering if there is a way to adjust the Chart's depth contour lines to match the actual depth I'm reading while on the water. For example if I look at the chart and I'm sitting on the 20 foot contour line, but the sonar actually reads 15 feet, can I adjust an "offset" to have the chart now show a 15 foot contour line instead?

Thanks....Richard

At this time there is no way to accomplish that on CMap. The only Maps that can do that is Lakemaster and those are brand H only these days as there is a patent for that technology. We would all like to have what you are talking about. Someday.

I don't think there is a "water level offset" feature on the C-Map chips.

I use a Navionics with my Elite TI2s and adjust my shallow water setting based on current lake ( 5ft + however many feet below full) then set fishing depth range min and max to whatever depth I want to fish + water depth below full pool ( it’s never above full on any of the south TX lakes).
Is that an option with C-Maps?

Yes you can do that with Depth Shading on all CMaps either Map Cards or Built in Lowrance Units like the HDS Live and FS Elite. This is not the same thing the OP is asking about but it is a good work around.

Thanks Larry for the feedback.