We present an experimental study for the generation of large 3D maps using our CoMapping framework. This framework considers a collaborative approach to efficiently manage, share, and merge maps between vehicles. The main objective of this work is to perform a cooperative mapping for urban and rural environments denied of continuous-GPS service. The study is split in to 2 stages: Pre-Local and Local. In the first stage, each vehicle builds a Pre-Local map of its surroundings in real-time using laser-based measurements, then relocates the map in a global coordinate system using just the low cost GPS data from the first instant of the map construction. In the second stage, vehicles share their pre-local maps, align and merge them in a decentralized way in order to generate more consistent and larger maps, named Local maps. To evaluate performance of all the cooperative system in terms of map alignments, tests are conducted using 3 cars equipped with LiDARs and GPS receiver devices in urban outdoor scenarios of thé Ecole Centrale Nantes campus and rural environments.