Earth Relief File Dimensions

Please can someone explain why the file dimensions for 01d in

are 361 x 181, whilst the file dimensions for 01d in

are 360 x 180 ? Why is there an extra degree in the first file?

Also, the file dimensions in need serious revision. Their values are not correct.

Pixel vs grid line registration

What dimensions (other than size) are wrong - they look good to me

a/ Is the comment ‘Pixel vs grid line registration’ explaining why there is an extra degree? Is there some online page that explains this in greater detail, please?

b/ In the file ‘’ there are 10 files with the same dimensions.

Are you aware that original SRTM grids are grid registered and when you find them with pixel registrations they were subjected to a destructive grid change?

See GMT documentation on that topic

I found this, which explains it. Thank you.