LiDAR based surveys have become increasingly common throughout the last decade. LiDAR is a remote sensing technology that measures distance by illuminating a target with a laser and analyzing the reflected light. These surveys are performed with the use of Laser Scanners. These can be classified in different ways, but a major distinction is between Terrestrial Laser Scanners and Mobile Laser Scanners.
Terrestrial Laser Scanners are fixed on tripods (very much like Total Stations) on a series of reference stations from which the objects are scanned. The use of different reference stations to scan permits covering the entire area of interest (by scanning from different angles) and further gives redundancy.
Mobile laser scanners don't have to be fixed, with scanners being placed on mobile vehicles (such as cars or boats) permitting a much quicker survey in terms of fieldwork and/or collecting a larger amount of information.
These surveys produce three dimensional digital representations of objects (buildings, bridges, roads, etc) with a high degree of precision and with a variable degree of detail (according to the Clients' needs). In terms of deliverables, the following can be produced:• Infra-structure mapping with LiDAR;
The use of Mobile Laser Scanners further allows making surveys in areas of difficult or limited access (urban roads, rivers, airports, etc). With digital models, a more comprehensive analysis is possible, as inspections can be performed based on such models. These can also be incorporated in BIM models, with particular significance when constructing models of existing buildings where as-built information does not exist or that does not correspond to the actual site situation.