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UAVs and 3D Laser Scanning Help Make Asbuilt Surveying Better-Faster-Cheaper-Safer (Sometimes)

by Mike on July 14, 2015

Using UAVs (Unmanned Aerial Vehicles) to obtain three-dimensional laser scanning is a great new addition to the surveyor’s toolkit that is improving the way we do land surveying these days, when the task at hand is to measure and record locations and elevations of the built environment. Three-dimensional (or 3D) laser scanning equipment is a camera-like device that sits on a tripod (or is mounted on a vehicle) and automatically scans the surroundings in a 360-degree sphere. As it does so, it creates an image-like digital record file in which every “pixel” is actually a point encoded with the three-dimensional coordinates of that spot, relative to local site control, together with attributes describing the light wavelengths reflected back to the instrument.
This technique creates an output that looks like a panoramic photograph, but which also can be post-processed to determine precise dimensions and elevations between all the features recorded, as well as their relative position on the earth. And it does so in a matter of seconds, collecting millions of individual measurements with each scan.
The technology is fast and reliable, and like so many new technologies today it gets less expensive by the day as experience and insight expand. And that better – faster – cheaper – safer equation is multiplied when it is applied to the need to record timely, detailed and accurate details of layers of infrastructure as they are built, installed, and finished or paved over, during the construction phase of a project.
Using 3D laser scanning means we don’t have to physically access remote or treacherous facilities to precisely measure them. We also can quickly generate a comprehensive, detailed, and complete record of everything within a 300-foot sphere from each set-up. The digital point cloud file which is collected each time can be stored as is or converted to Computer-Aided Drafting (CAD) or Building Information Management (BIM) deliverables. The CAD or BIM deliverables can be developed in total initially, or the data extraction can be delivered incrementally over time (as long as nothing changes, of course), further controlling costs.
The nature of the process means that projects can afford to schedule multiple periodic or timely scanning events to compile valuable data layers. It also means that ongoing construction or production in the vicinity can be spared costly interruptions or time-wasting delays. This also keeps surveyors out of traffic and safe from hazards.
The complexity or detail of the structures is not a problem for the scanner.  Scans of features obstructed from one point of view can be filled in from supplemental scans from another set up to eliminate data gaps.
The panoramic imagery also records not just the location, but the color, shape, and texture of the objects. Visible labels and signage are legible in the final product, too. All the details are captured: cavities, recesses, tunnels, arbors, facades, interior / exterior equipment, and piping. Scanning can be done indoors or out, even in low-light conditions for after-hours operation, although photo-realistic capture of colors, materials, textures do require more. 3D scanning is the optimal method for generating BIM input to assure a solid start to 3D design and structure matching.
A UAS or Unmanned Aerial System (“system” in order to encompass the entirety of the vehicle that flies, the ground-based controller, and the communications connection that connects the two) is an ultra-light unmanned aircraft carrying LiDAR scanners (Light Detection And Ranging) and high-resolution cameras with real-time GPS receivers can facilitate capturing pipes in trenches, footings, foundations, tunnels, arbors, structural steel, and open floors as they are built on a daily basis (or as needed).   Because as-built data image captures happens much quicker than traditional on the ground survey methods construction crews don’t have to leave the new improvement exposed for long periods and construction progress is not impeded.
Another advantage to using UAS to survey facilities is that you can update a selected portion of the aerial photo layer in your BIM / Facilities GIS instead of having to periodically fly a new layer in its entirety. No more dealing with out-of-date aerial images, or having to bear the cost to fly areas on an annual basis that otherwise are unchanged.
These are just a few of the uncommon ways we will be using GIS and UAS technology to perform as-built surveys, existing conditions surveys, inventories, and site surveys for new construction. We are being proactive, and beginning with the end in mind, to maximize the potential in these cost-saving and safety-improving techniques.
A comprehensive geographic database with a common workflow interface can help increase revenue, lower costs and mitigate risk.  3D laser scanning and drone technology can help make it happen better, faster, cheaper, and safer.