Fresh start with continental map

[bartmoss]

I was afraid someone would call me out on that, I just hoped it would not be within 30ish minutes. Yeah, I am terrible at the math involved, so I try to wing it. I did throw a Canada map in as my reference layer, though, for that very reason. This is the grid they used:



Looks similar to what you use, at least to my very untrained eye.

As an aside, is there an easy way to convert that sort of thing back to Equirectangular?

[Hai-Etlik]

I was afraid someone would call me out on that, I just hoped it would not be within 30ish minutes. Yeah, I am terrible at the math involved, so I try to wing it. I did throw a Canada map in as my reference layer, though, for that very reason. This is the grid they used:



Looks similar to what you use, at least to my very untrained eye.

I wasn't trying to "call you out", I was just pointing out that this was something that could bite you if you weren't wary. For instance, you can't put a compass rose on this map. I wasn't saying that you need to include a graticule for instance just that if you do, it needs to be a fairly specific one.

They are both Conic projections, which is fairly typical of maps of this extent and position and is why they look similar. I'd need to look at how the graticule distorts as you move away from the standard parallels to make a guess as to which particular conic projection it is.

As an aside, is there an easy way to convert that sort of thing back to Equirectangular?

If you're working in a GIS from the start, yes, but then you probably wouldn't be asking. With plain graphics tools, no, not really as it requires georeferencing the image, which is tricky unless you stick to normal aspect cylindrical projections (which this is not).

That's why easy tools like G.Projector can't do inverse transformations. Also, some projections don't have closed form inverses which means you have to use complex, slow, and inaccurate numerical methods to reverse them even if the image is georeferenced. The commonly used conic protections do have closed form inverses though.

PS: Here it is in Plate Carree/Equirectangular The georeferencing isn't the greatest and it lost a lot of resolution in the process

[bartmoss]

And I figure I should probably add the "latest" WIP - it's been a while since I touched this map.