Tunnel mapping system and methods

A process for constructing highly accurate three-dimensional mappings of objects along a tunnel in which, at least in portions of said tunnel GPS signal information is not available, said tunnel having rails for accommodating railroad or subway cars, or the like, comprising:

• a. providing a vehicle for traversing said tunnel on said rails;
• b. locating on said vehicle
• i. a LiDAR unit,
• ii. a mobile GPS unit,
• iii. an inertial navigation system, and
• iv. a speed sensor to determine the speed of said vehicle,
• c. locating near the entrance of said tunnel a stationary GPS, whose geolocation is well-defined;
• d. locating image-identifiable targets at preselected locations within said tunnel, said targets having well-defined geodetic locations;
• e. adjusting said mobile GPS unit based on said geolocation of said stationary GPS;
• f. traversing said tunnel with said vehicle, said LiDAR thereby producing mass point cloud datasets along said tunnel;
• g. obtaining precise measurements of 3D rail coordinates, including at least one of superelevation and track center;
• and
• h. adjusting said point cloud datasets based on said mobile GPS unit, said inertial navigation system, said speed sensor, said location of said image-identifiable targets, and said precise measurements of 3D rail coordinates, to thereby produce highly accurate, and substantially geodetically correct, three-dimensional mappings of objects along said tunnel.