If you say that people camp out somewhere in the open air, you are emphasizing that they stay there for a long time, because they are waiting for something to happen. [emphasis]
...reporters who had camped out in anticipation of her arrival. [VERBPARTICLE]
2. camp [sense 4]verbB1+
If you camp somewhere, you stay or live there for a short time in a tent or caravan, or in the open air.
We camped near the beach. [VERB]
...the men, who are camping on the pavement in sleeping bags. [VERB]