campground vs camping ground

campground and camping ground both are nouns.

Word	Noun	Adjective	Verb	Adverb
campground	Yes	No	No	No
camping ground	Yes	No	No	No

As nouns, campground and camping ground are synonyms defined as:

campground and camping ground: a site where people on holiday can pitch a tent

Other synonyms of campground include bivouac, camping area, camping site, campsite, encampment.

campground (noun)	camping ground (noun)
a site where people on holiday can pitch a tent	a site where people on holiday can pitch a tent