Commercially introduced in the late 1990s, laser surveying, also known as laser scanning, has grown in popularity in recent years. Today, surveying companies that wish to remain competitive must own a laser scanner, and often more than one. Although GPS surveying remains a standard service, its drawbacks are causing an industry-wide switch to using lasers - a change that some surveyors have already embraced.
One example of a surveyor that successfully transitioned from GPS to laser scanning is LandAir Surveying, a Georgia-based company that started doing business in 1988. They performed topographic surveys and site surveys for contractors in Georgia and surrounding states. Like most surveyors who graduated to laser scanning, LandAir used GPS into the early 2000s, when a specific project revealed the need for an equipment upgrade. For LandAir, that project was the Georgia Department of Transportation's need for an As-Built condition survey for an eight-lane bridge, which was too wide and long for GPS devices to survey with accuracy.
After attending a laser scanning demo by a Leica Geosystems representative in 2005, LandAir purchased the Leica 3000, and today uses Leica's HDS6100, HDS6000, and ScanStation II scanners. Initially using its equipment for conventional projects, LandAir expanded to projects whose size and complexity needed laser scanners. Examples included as-builts of large interiors and structural support surveys. The values that LandAir's early scanning clients saw in laser surveying are the same value that it holds today: The ability to survey a broader variety of objects, environments, and structures, and to complete a surveying project in as little as one surveying session. Also, the collection of more precise data than GPS or total stations and the delivery of editable data models that clients can manipulate, thus decreasing surveyor involvement.
As LandAir discovered in 2005, surveyors who switch from traditional surveying to laser surveying do more than swap equipment; they also change how they conduct the surveying process. When switching from GPS, field notes become a thing of the past and were replaced by endless data points and photographic files; a traditional line of site to the next surveying point is abandoned for more focused coverage; and laser scans often capture more data than a client initially needs but eventually finds useful, which decreases surveyor involvement. From a client perspective, the laser surveyor's decreased involvement has two benefits. It allows clients more freedom as facilitated by editable project data, and it drives down the surveying cost despite scanning equipment's higher price than GPS.
What are the Steps in the Laser Scanning Process?
The laser scanning process has three basic stages. First, a scanning provider will "mark out" the entire structure or environment to be scanned in order to identify the number of scanning stations and the position of the scanner in each station. In the case of small to mid-sized object scanning, the station and position of the scanner are often already obvious. Next, the scanning commences, which accounts for roughly 80 percent of the scanning process. After the scanning is complete, the scanning provider will download the scan data to a computer and process it according to the customer's wishes, after which it is delivered to the customer.
How Long Does the Laser Scanning Process Take?
Depending on the type of scanner used, a single shot can take anywhere from two minutes to two hours. Phase shift scanners generally take between five and ten minutes to complete a shot, whereas time of flight scanners can take up to two hours to complete a shot. However, for a large project, multiple scanners can be used simultaneously to decrease the duration of the scanning process.
Is it Possible to Conduct 3D Laser Surveying at Night?
With the technology of today's laser surveying equipment, it is possible to conduct 3D laser surveying at night. While it might seem unusual that laser surveying would be conducted at night, surveying buildings and objects are surrounded by public streets and sidewalks. Therefore, they are packed during the day, which makes surveying late at night and early in the morning advantageous.
Can a Laser Scanner Scan Through Water or Glass?
Due of the unreliability of the scan data, laser scanners are not used to scan through transparent substances such as water, glass, plastic, etc. Although the scanner's laser beam can pass through transparent and semitransparent substances, the substances cause the beam to diffract, which results in highly unreliable scan data.
Is it Possible to Laser Scan in Color?
Some scanners can be used to capture in color the objects that they measure, while other laser scanners can be used in combination with a digital camera to generate color scans. However, color scans are of little to no use in industry and topography, and color scanning always results in a higher service price. One instance where color scanning can be beneficial, and is often preferred, is in the scanning of art installations before they open to the public.
Is it Possible to Scan a Moving Object?
Some scanners are designed for "dynamic scanning", which involves scanning objects that are in motion or scanning still objects while the scanner is in motion (e.g. mounted on a moving vehicle). However, the value of dynamic scanning depends completely on the scanning accuracy and exhaustiveness that is desired. Tripod mounted scanner yield the highest accuracy.
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