3D Laser Scanning
The concept behind 3D laser scanning is not new however the capability to manage and process the volume of data produced by scanning has only become realistic in more recent times. Scanning captures a multitude of points with x,y,z coordinates on the surface of the object being scanned. In addition the intensity of return signal can indicate the nature of the scanned surface and the capture of RGB values allows a photo-realistic representation of the modelled surface to be generated.
The examples below provide a further description of scanner capabilities and are worthy of reading to gain an overview of 3D laser scanning. It will become clear that scanning can be applied to a multitude of applications. We have experience with a wide variety of applications and an understanding of the most appropriate equipment for a given task.
Long range scanners can provide a safe method of scanning landslides or steep sites as an alternative to abseiling with reflector prisms or the alternative of slow reflectorless EDM technology. Sparse vegetation can be filtered out of the point cloud by setting criteria for intensity of the return signal (lower off vegetation than hard surface). The scanner can have a pre-set mask applied to limit the data captured to a particular area of interest. For example traffic interrupting line of sight for a scan can be excluded from the scan by setting a mask which excludes objects within a certain distance range from the scanner station. Likewise a mask can be set to limit the “field of view” scanned in order to reduce data volume.
Laser scanning is an ideal tool for capturing existing plant details to allow for pre-fabrication of replacement or additional components. Post scanning software allows for auto completion of pipes, ducts and structural members. Where scanning costs could be significant as a result of time demand to process the point cloud into a 3D model continuing software advances mean that the ratio of scanning time to processing / modelling time is reducing and scanning can now become a competitive alternative to manual measure-up methods.
Scanning of Structural Members for Seismic Design
Laser scanning can provide quick non-intrusive access to as-built existing structures. Although laser scanning is “line of sight” it is possible to auto complete structural members such as I beams from single sided scans by selecting appropriate cross-sections from a structural steel spreadsheet during scan processing. Elevating tripods or scanner setups on staging or scissor lifts, with scanner control by WiFi, allow for scanner positions which may be difficult or unsafe to access to employ the use of conventional surveying equipment.
Scanning now provides an alternative to terrestrial photogrammetry for capturing complex historic facades. Intensity of the return signal (shown by colour gradient) provides an indication of the surface material being scanned. The scanner captures RGB (red, green, blue) values as an attribute with each scanned point allowing a near photographic representation of the façade. Alternatively many scanners will capture jpgs as part of the scan routine.
Scanning provides an ideal tool for monitoring of structures such as building under demolition or for condition surveys of buildings adjacent to demolition or de-watering sites. In many cases an intense baseline scan is carried out followed by periodic comparison scans at a lower intensity. A bi-product of the scan comparison can be a histogram showing relationship of mean positions of the baseline and subsequent scans. Our understanding of statistical concepts allows us to report on deformation (or not) within meaningful data confidence limits.
Geometric Measurement & Testing
Laser scanning has been used for a huge variety of geometric testing from circularity/shape of vehicle tyres through to fuel storage tanks. Laser scanning provides an alternative to traditional peaking and banding surveys of fuel storage tanks. We have also had experience with scanning of aircraft for a variety of applications. Scanning has been employed in shipbuilding for pre-fabrication of repairs and hull lengthening