irregular grids

[a.larkin@xxxxxxxx (Alice Larkin)]

Hello, I'm afraid I'm another new user with a probably trivial problem, but
would welcome some help.
I have a set of ascii data 17 rows by 19 colunms. The columns are lines of
latitude, -85:85. The rows are vertical heights measured in scale height of
1000*e-x where x is 0.25,0.75...8.25. (e.g 778.8mb,472.4mb...) So, my vertical
 heights increase inregularly. How then do I define a grid for this and the
 axis?

Cheers.
Alice Larkin