longitudinal

longitudinal /ˌlɑːnʤəˈtuːdənəl/ Brit /ˌlɒnʤəˈtjuːdənəl/ adjective
longitudinal
/ˌlɑːnʤəˈtuːdənəl/ Brit /ˌlɒnʤəˈtjuːdənəl/
adjective
Britannica Dictionary definition of LONGITUDINAL
always used before a noun
1 
: placed or going along the long side of something
2 
: of or relating to longitude
3 
: done by observing or examining a group of people or things over time to study how one or two particular things about them change

— longitudinally

adverb