longitudinally

from WordNet (r) 3.0 (2006)

longitudinally
    adv 1: across time; "We studied the development of the children
           longitudinally"
    2: in the direction of the length; "He cut the paper lengthwise"
       [syn: {lengthways}, {lengthwise}, {longwise}, {longways},
       {longitudinally}]
    3: with respect to longitude; "longitudinally measured"

from The Collaborative International Dictionary of English v.0.48

Longitudinally \Lon`gi*tu"di*nal*ly\, adv.
   In the direction of length.
   [1913 Webster]