The Earth's Curve

[Slim]

This is a photo that I took in Wales in March, on the Pembrokeshire coastal path.



The camera (actually a Samsung phone) was only about 20 - 30 metres above sea level when this was taken. But I wondered if I'd be able to see the curve of the horizon if I compressed the pic sideways, like this (image is cropped but shows the whole breadth of the first image):



Although it's tempting to blame the curvature present in the image on lens distortion, I don't think that's the case here. The horizon was actually slightly below the centre of the image, so any barrel distortion would tend to suppress the curve, not exaggerate it. However I have no idea how to do the maths for the degree of curvature you'd expect to see from that elevation. So I suspect that is just an exaggerated view of the Earth's curvature.

Anyone any thoughts?