De or het lengtebepaling?

The correct Dutch article is:

de lengtebepaling

Rule Words ending in -ing: almost always de. See the rule

How to use lengtebepaling

the lengtebepalingde lengtebepaling
this lengtebepalingdeze lengtebepaling
that lengtebepalingdie lengtebepaling
our lengtebepalingonze lengtebepaling
your lengtebepalingjouw lengtebepaling
every lengtebepalingelke lengtebepaling
which lengtebepaling?welke lengtebepaling?
a big lengtebepaling / the big lengtebepalingeen grote lengtebepaling, de grote lengtebepaling