The key to navigate in a 3D environment or designing autonomous vehicles that can successfully maneuver and manipulate objects in their environment is the ability to create, maintain, and use effectively a 3D digital model that accurately represents its physical counterpart. Virtual exploring of real places and environments, either for leisure, engineering design, training and simulation, or tasks in remote or hazardous environments, is more effective and useful if geometrical relationships and dimensions in the virtual model are accurate. A system which can rapidly, reliably, remotely and accurately perform measurements in the 3D space for the mapping of indoor environments is needed for many applications. In this paper we present a mobile mapping system that is designed to generate a geometrically precise 3D model of an unknown indoor environment. The same general design concept can be used for environments ranging from simple office hallways to long winding underground mine tunnels. Surfaces and features can be accurately mapped from images acquired by a unique configuration of different types of optical imaging sensor and dead reckoning positioning device. This configuration guarantees that all the information required to create the 3D model of the environment is included in the collected data. Sufficient overlaps between 2D intensity images, in combination with information from 3D range images, insure that the complete environment can be accurately reconstructed when all the data is simultaneously processed. The system, the data collection and processing procedure, test results, the modeling and display at our virtual environment facility are described.