How do I draw appropriate sea charts?

[Nyasupan]

I'm planning drawing a sea chart for a world of my creation for a D&D game. I would like to draw those lines and grids in the sea that, for what I understandm, are a tool for keeping a naval route while at sea. I want to try and replicate something like this map I found online but I don't quite understant how to appropriately draw those lines.

DeVries-_-DeVries-antieke-prenten-lres-024_grande.jpg

Could someone who has a much better understanding of how these type of maps work help me with this project? What mesurements and points I have to track to appropriately draw those lines?

Thank you in advance for your time.

[Falconius]

It's just the four points of the compass divided then either divided again and again, or split into thirds. All the points line up along lines emanating from other roses and it's fairly easy to get them to all intersect since they all share common angles. So once you make one you can just copy and paste it along the lines and it will line up nicely.

windrosenetworkreduce.png

Which is all made from one of these:
Rhumb Linesreduce.png

I used inkscape to do mine. Here is the SVG file, although I've never uploaded one before so have no idea if it'll work correctly. I think if you just delete the circle objects it'll just show the lines underneath.
WindroseNetwork.svg

[Nyasupan]

Oh... and so i thought there was some science behind it. Thank you very much!

[Falconius]

Well there is, but it's more to do with the map projection being used. The lines show a constant compass bearing from those roses that ships can follow to get to the next one and so forth. But for the purposes of fantasy maps the projection really doesn't matter too much until you start getting into mapping an entire globe. And even then you can fudge things around to work.