# What kind of projection is that?

I found this figure in the paper: Atlantic overturning: new observations and challenges by Srokosz et al. I wonder what kind of projection this is and what the advantages of it are? It looks to me as if the surface orgin. Do you have more information

(Fig from: Srokosz et al)

It looks to me like a sinusoidal projection centred on -30°W, with edges at -90°W and 30°E. For that projection, the length of the parallels goes as cos(latitude), so we expect the ratio of the widths of the map at 75°S and at the equator to be 0.26, which agrees exactly with my quick measurement of the figure.

The sinusoidal projection is equal area, but I think in this case they also like it because its east-west scale is constant. All the labeled lines on the map are roughly east-west, so their relative lengths on the map are all roughly correct. For example, we can immediately see that real length of the "SAMBA 34.5°S" track is more than twice as long as the "NOAC 47°N" track.

• A nice feature of that projection is that while distances at angles other than east-west are distorted, it's intuitively clear how one would need to adjust the map to make it more accurately represent the shape of some part of the Earth, and how such adjustment would affect the size. Commented Jan 20 at 19:55