De or het routeplanning?

The correct Dutch article is:

de routeplanning

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

How to use routeplanning

the routeplanningde routeplanning
this routeplanningdeze routeplanning
that routeplanningdie routeplanning
our routeplanningonze routeplanning
your routeplanningjouw routeplanning
every routeplanningelke routeplanning
which routeplanning?welke routeplanning?
a big routeplanning / the big routeplanningeen grote routeplanning, de grote routeplanning