Site Scanning using Photogrammetry
Photogrammetry : Measurements Using Photographs:
With the Geo-tagged photos obtained by the UAS, an orthoimage can be generated from the marked ground features, including Streams, Vegetations, Buildings, can be evaluated and measured accurately. Such information can be essential during Design Phase to plan projects, such as site entrances, drainage design, waste generation estimation, designing mitigation / protection measures etc.
Site Planning and Control:
During construction phase, a regular site map can show the progress of the construction. Using Geo-tagged maps, Engineers can easily compare the progress at fixed time interval and identify any potential issues, plan ahead and foresee potential issues or milestones, without being physically on site. As such, Engineers and Management can remotely monitor progress, reducing costs and boost efficiency.
Alignment Verification:
Marine Works including reclamation can be difficult to control, but UAS can easily fly over the sea water to verify the coordinate of the area, and through the generated map engineers can estimate the boundary of the seawall and compare if any drifting observed. Same technology can also be applied on land, including road works and viaduct works, which are difficult to visualize the progress of a large-scale infrastructure projects.
3D Scanning using Photogrammetry
Photogrammetry : 3D Model Generation:
The photos taken by the UAS can be combined to create a 3D geo-model, which enables engineers and management to conduct further assessment, including Stockpile Estimation, Historic Monument Recording, Topography Survey, etc.
Stockpile / Excavation / Landfill Capacity Estimation:
For construction sites with extensive excavation, or for landfill sites needed to estimate the capacity, UAS can quickly estimate the capacity by post processing of the photos to generate a 3D object, and through the process the ground features can be assessed and parameters including the excavated volume and the stockpile volume can be estimated. Compare to traditional surveying technique, this greatly reduce the time and improve efficiency.
Historic Monument Record:
3D images provide more details than 2d photos for large scale monument, e.g. historic buildings, historic sites, which enable archaeologists to study the monument off-site and reduce the need to re-visit the remote and time consuming sites.
Other Scanning Capabilities
UAS as a platform can mount any kind of scanners and sensors and conduct surveys at high elevations without land-based blockage.
Infra-Red Sensors
Infra-Red sensors is a powerful tool in vegetation inspection, by calculating the absorption of Infra-Red of a plant, the Normalized Difference Vegetation Index (NDVI) can be obtained. NDVI gives a indication on the healthiness of a plant and alert the manager if the plant are under stress. This is especially important for forest managers to manage a large area of forest efficiently and effectively.
Thermal Imaging
Similar to Infra-Red Sensors, Thermal Imaging records the temperature of the object under inspection, as structures taking up heat will develop a temperature pattern depends on the direction of heat source. However, if there is a structure flaw, heat transfer through the flaw will be interrupted and results in a irregular pattern, such that these structure flaw can be identified. Thermal Imaging has been widely used in highway inspection to identify road structure integrity and help in repair scheduling.
Topography Survey or 3D Model Generation - BIM Compatibility
With the latest development of laser scanner, a light-weighted laser scanner can now perform scanning at mid-air and penetrate vegetation to estimate the topography of the site before project start.The time required for a laser scan can be reduced to minutes for site area of 5 hectares. CAD and BIM compatible shape files can be obtained from the scanned results and is an excellent tool for building model assessment.