Reply With Quote
I think you're talking about rhumb lines. Take a look at this thread. Someone asked the same question a while back.
What are the lines in the backgrounds for?
I've seen them used in some maps, what are they for? I'm talking about those Radial lines that intersect in one or two points on the map. Sometimes they're around a compass.
I think you're talking about rhumb lines. Take a look at this thread. Someone asked the same question a while back.
"We are the music makers, and we are the dreamers of dreams"
Do I still need them if my map is grid based instead of a projection?Originally Posted by ChickPea
It's entirely up to you. They're meant as navigational aids, so if that's not the focus of your map, then they're not necessary. Having said that, I suspect most people around here use them more for decorative purposes, rather than any serious attempt at a navigational map, so whatever works.
"We are the music makers, and we are the dreamers of dreams"
You need them if you are a sailor using the map to navigate...
And what you mean by grid-based is probably a form of projection, since all maps have some projection. Not all navigational maps had rhumb lines to start with and, for some time, they were actually misleading when the maps weren't local (like, restricted to the mediterranean sea, for example). It was only during the Age of Discoveries that maths was applied successfuly to world mapping and that the Mercator projection was developed. Rhumb lines are only actual rhumb lines in a Mercator projection. Any other projection and they couldn't be straight while maintaining a "rhumb" (a bearing). Still, in some other maps they are drawn for decorative purposes, since they give them a more classical - age of discoveries look
Depends:
- are you making a map with the ultimate purpose of looking cool to your eyes? in that case, either way, it's up to you.
- is the map you're making supposed to be used for navigation in "your world"? in that case, yes, if the world is set in any age from high-medieval to modern, but mostly if you aim for a nautical feel
- is your map "drawn" in an age any earlier than say 15th century? then they wouldn't have the working knowledge to think about or use rhumb lines
Rhumb lines are functionally equivalent to a compass rose. They indicate that the map preserves compass bearings, how those bearings relate to the map, and provide a built in reference for measuring bearings on the map (Instead of trying to align a separate protractor with the map). Not all maps are bearing preserving, and any maps that aren't should not have compass roses or rhumb lines because it's equivalent to writing "This map is bearing preserving" on them.
Any map of a world that is not flat is projected. The projection may be an inconsistent, ad hoc mess, but it's still a projection. "Do I still need them if my map is grid based instead of a projection? " therefore doesn't really make sense. Could you explain what you are up to more clearly so that we can give you a better answer?
To clarify an assumption in all of the explanations: if your world is spherical and you draw it on a flat surface, then there will be a projection involved that introduces some sort of distortion. If your world is flat (we'll leave out toroidal or any of a number of other geometries), then rhumb lines would only be meaningful if it sports something like fixed magnetic poles and a device for pointing at them like a compass. A directional field would be even better because you wouldn't need to show the rhumb lines as curved.
The ideal navigation device for a flat world that doesn't work long range on a globe is a resettable point compass (always points toward a specific point or object on the surface). A few point compasses locked to widely-spaced points around the world would allow perfect location at any time, especially if distance estimates are also available. It doesn't work as well on a globe because it starts to point down as you go over the horizon.
Thank you guys. I have decided not to use them since I do not fully grasp the concept behind it, my map is more of a Equirectangular type of map and is not made for navigation. Thank you for answering
I was wrong when I said that everyone made a bad assumption. As Hai-Etlik pointed out, "Any map of a world that is not flat is projected."
Posting Permissions
