Drawing areas of of different scales

[mimon]

This question is not directly related to nautograf, but something related to ENC software in general. I'm writing my own ENC viewer and I found nautograf as a great source of inspiration. Thank you for sharing the code by the way (!). I haven't found a place/community on the internet for ENC software makers so I thought I'd take a chance and post my question here.

Like nautograf, my ENC loads .oesu files (purchased from o-charts.org). Let's say I have file A and B where B is covering a smaller part of A but at a higher scale. If I render A and then render B (on top of A), and only rendering land areas and depth contours it looks cluttered. The lines from A is kind of overlapped by the lines from B, but slighyly off, due to the higher scale in B(i think?).

I wonder how you've solved it in Nautograf? How does one render sub sections of higher scale on top of a lower scale areas? Unfortunatly, I'm not on a windows machine so I can't run nautograf and see how nautograf has solved the problem visually at least.

[mimon]

I ended up not blending two charts with different scales. I think I have misunderstood how charts work, I was under the impression that charts could add more detail in layers on top of others. Mainly because I was observering that some of my rendered charts had "holes" with no geometry. Turns out those were objects of type which I didn't render.

Sorry to bother here :)

[hornang]

Thanks for sharing your problem! Looks like you found out what to do by now, but I can share my thoughts.

My experience is that you shouldn't need to blend graphical elements across charts. If you have a higher resolution chart, you should render that on top of lower resolution charts. The chart files have a coverage polygon (M_COVR) that you can use to wipe out the graphics from the lower resolution chart below. The coverage polygons should also show what the actual chart file covers which is very often less than the lat/lon rectangle of the chart file.

[mimon]

Awesome, I didn't know about the coverage polygon. I have been looking for/wondering about exactly that. Thank you!