Linear Sand Dunes.
http://earthobservatory.nasa.gov/IOTD/view.php?id=51190
https://books.google.com/books?id=NU_wAAAAMAAJ&pg=PA355&lpg=PA355&dq=botswana+linear+dunes&source=bl&ots=s-DAvC6NU9&sig=pz9OsFiiZokaED1fjfIK2S11B1A&hl=en&sa=X&ei=vLCoVNTYJozsggS_1YPwBQ&ved=0CEIQ6AEwBQ
That could be right, but in close-up they do not look like linear sand dunes: 
That could be right, but in close-up they do not look like linear sand dunes: