What is this thing?

[daan]

Obviously an azimuthal, probably equidistant, with the southern hemisphere sliced into lobes, but I don’t think I’ve seen this arrangement. Anyone have a name for it?

Cheers,
— daan

shm-bar (1).jpg (153.12 KiB) Viewed 10600 times

[mapnerd2022]

Isn't that a 4 lobe variant of the Berghaus projection?

[daan]

Isn't that a 4 lobe variant of the Berghaus projection?

Well… I wish the image were better so that I could understand the geometry better. But it looks to me like the lobe edges are curved, which would not fit a Berghaus-like star. It also looks like it’s unfolded into two parts, not four, because (I think) the gap between the two upper lobes is much narrower (or nonexistent) than the gabs between the upper and lower lobes on the side. Maybe the curved lobe edges and the gap inconsistency is simply because the map is not actually the whole world, but instead has been trimmed.

— daan

[Milo]

I don't know. It doesn't appear to be any of the seven projections listed with "pole-centered fusion" on this page.

But it looks to me like the lobe edges are curved, which would not fit a Berghaus-like star.

There are certainly known star projections with curved lobes, such as William-Olsson (interestingly not named after two discoverers who were William and Olsson, but rather after a single person whose name was William-Olsson).

However, the real problem here is the angle that the lobes are split at, which is much shallower than I would expect from a lobed projection. It must mean that the meridians are kinked.

It also looks like it’s unfolded into two parts, not four, because (I think) the gap between the two upper lobes is much narrower (or nonexistent) than the gaps between the upper and lower lobes on the side. Maybe the curved lobe edges and the gap inconsistency is simply because the map is not actually the whole world, but instead has been trimmed.

That could just be an artifact of the non-square aspect ratio. I did a quick pixel measurement in a graphics program, and it seems like the distance from the center to the inner corners of the left/right gaps is about the same as the center from the center to the top of the map, which means that even if there is a lobe split there, only a few pixels at most should be visible.

It's also hard to imagine what the (hidden) top/bottom edges should look like if the map does have only two lobes. The lobes are curved, but the curvature is fairly slight, so unless it drastically increases off-screen, it would take white a long while for them to manage to loop back in on themselves.

[Atarimaster]

There are certainly known star projections with curved lobes, such as William-Olsson

Yes, William-Olsson was my first idea – but then I saw that the shapes of the continents did not seem to match. And even more apparent (but I realized that a bit later), the lobe split starts at 20°N on the William-Olsson, while here it’s at the equator.

It also looks like it’s unfolded into two parts, not four (…)

That could just be an artifact of the non-square aspect ratio. I did a quick pixel measurement in a graphics program, and it seems like the distance from the center to the inner corners of the left/right gaps is about the same as the center from the center to the top of the map, which means that even if there is a lobe split there, only a few pixels at most should be visible.

I agree, the lobe splits at the top and bottom are “off-screen”.
In this image, I’ve emphasized the equator:

shm-bar-mod.jpg (36.17 KiB) Viewed 10586 times

I agree that the map center looks equidistant (as far as one can tell from the image) rather than equal-area like in William-Olsson.
Maybe a four-lobe variant of the Hexafoliate Equidistant, i.e. a “Tetrafoliate Equidistant”?
I don’t know who developed the Hexafoliate Equidistant so I can’t check if it’s maybe just one instance of an “x-lobed projection with the azimuthal equidistant projection at the center”.

But I also agree that the angle that the lobes are split at look wrong…

[mapnerd2022]

I don't know. It doesn't appear to be any of the seven projections listed with "pole-centered fusion" on this page.

But it looks to me like the lobe edges are curved, which would not fit a Berghaus-like star.

There are certainly known star projections with curved lobes, such as William-Olsson (interestingly not named after two discoverers who were William and Olsson, but rather after a single person whose name was William-Olsson).

However, the real problem here is the angle that the lobes are split at, which is much shallower than I would expect from a lobed projection. It must mean that the meridians are kinked.

It also looks like it’s unfolded into two parts, not four, because (I think) the gap between the two upper lobes is much narrower (or nonexistent) than the gaps between the upper and lower lobes on the side. Maybe the curved lobe edges and the gap inconsistency is simply because the map is not actually the whole world, but instead has been trimmed.

That could just be an artifact of the non-square aspect ratio. I did a quick pixel measurement in a graphics program, and it seems like the distance from the center to the inner corners of the left/right gaps is about the same as the center from the center to the top of the map, which means that even if there is a lobe split there, only a few pixels at most should be visible.

It's also hard to imagine what the (hidden) top/bottom edges should look like if the map does have only two lobes. The lobes are curved, but the curvature is fairly slight, so unless it drastically increases off-screen, it would take white a long while for them to manage to loop back in on themselves.

That's because his first name was also William and, of course, like you said, his surname was William-Olsson.

[quadibloc]

I remember seeing something that looked a bit like that in a Readers' Digest world atlas.

[rschmunk]

I agree that the map center looks equidistant (as far as one can tell from the image) rather than equal-area like in William-Olsson.
Maybe a four-lobe variant of the Hexafoliate Equidistant, i.e. a “Tetrafoliate Equidistant”?
I don’t know who developed the Hexafoliate Equidistant so I can’t check if it’s maybe just one instance of an “x-lobed projection with the azimuthal equidistant projection at the center”.

The "Hexafoliate Equidistant" is something I coded up based on a projection I noticed in an 1898 American geography textbook, and re-printed in at least one other textbook by the same authors. These were geography texts and not cartography texts. There's little or no discussion of map projections in them. I have no clue how I first ran into these books.