Could Nick chip in on what the chart presentation depends on? I assume the panning and zooming relies on the GPU of the computer and not the CPU, correct?

C-Map MAX is all done in the CPU. 4D is done on the GPU, although there is some over-head in getting it from OpenGL to DirectX. RNCs and ENCs are all rendered in the GPU, although there is obviously a lot more work involved in rendering an ENC.

The C-Map data is always on levels, that span a fixed range of display scales. We can select by evel or scale. This will have been for simplicity of the user interface, esp on plotters.

The MAX has an ability to under-zoom at each display level, but I am not sure how useful that really is. Exp has that on the settings page. It might have been useful for Vestus where the data was missing at some levels (also on Navionics and Garmin I believe).

So, it probably would be possible for the slider idea for MAX, but ...

With ENCs, each object has an attribute to specify at which scale it is displayed. This is why some objects will disappear as you scale out. The important ones will remain. Obviously this is mostly for cluttering considerations. I am reluctant to over-ride that as the intention is to stay as close as possible to the IHO standards.

On the earlier question I am currently working on a mode to be able to pan and change charts at about the same scale.