Structural Surveying
May 23rd, 2013
Image by Travis Gray
toned digitally.
Introduction
The notion of surveying buildings and other manmade structures is almost as old as the pyramids. Combining the elements of measurement and observation, structural surveying is critical for everything from initial building to historical preservation. Methods have changed over the years as technologies has emerged to offer more rapidly, less complicated and a lot more precise final results.
Methodology
Drawings of 2D and 3D creating façades, plus 3-dimensional representations of all sorts of other structures, allow engineers to develop, repair or restore them while keeping track of progress in actual time. The nature of surveying is to generate lines of sight that reproduce an image of the object in query. For new construction, this indicates the suitable alignment of footings on the ground that matches the blueprints. In a restoration project, this means re-creating the original style in 3 dimensions and then employing those drawings to exactly repair or replace structural components. The accuracy one can obtain by using surveying strategies and equipment guarantees that almost everything is in its appropriate location. This is not only crucial from an aesthetic point of view in some situations, the structural integrity of the building may endure if repaired surveying gear components are not in precise alignment.
Traditional Benchmarking
In constructing restoration, surveyors use a total station-the ultra-modern, electronic version of the transit that measures angles and distances with incredible accuracy-to locate the centers of the target object. From these center points, further points are measured that represent edges, corners, line finish-points, and other outstanding characteristics. For an typical building, it is not uncommon to see a surveyor gather hundreds of points to obtain an suitable level of accuracy.
The purpose of benchmarking is to locate specific surface features and insert them into some sort of map or drawing. With the advent of CAD (personal computer-aided style), it is attainable to download data collected by the total station straight into a drawing system. With a level of accuracy that ranges from amongst 2mm and 5mm, classic methods are usually adequate for most projects.
Laser Scanning and Benchmarking
The introduction of the laser scanner as a tool for structural surveying has resulted in three direct rewards. Very first, the time a surveyor spends onsite is significantly reduced. A surveyor who requires two or three days to collect information with a total station can easily see his or surveying equipment her function hours cut in half-or much more-with a ground-primarily based laser scanner mounted on a tripod. Second, the number of points a surveyor can collect with a laser scanner will jump from the hundreds into the thousands. The more points that are collected, the far better the final image seems in a CAD atmosphere. Third, an accuracy level in the neighborhood of 1mm to 2mm is clearly achievable with scanners, especially provided the point density that is a result of laser technologies.
Borescopes and Endoscopes
Another tool accessible to the structural surveyor is the borescope. Also known as an endoscope-a term borrowed from medicine-this device is used for observing and measuring the insides of structures that are not readily accessible, all without having negatively affecting structural integrity. In this approach, a borehole is drilled into the outer wall of the structure-generally 12-13mm in diameter-through which the scope is inserted. All sorts of structures can be observed this way, such as ductwork, voids beneath and among floors, and spaces in ceiling and roof places. Most borescopes come equipped with fiber optics for illumination purposes and are oftentimes connected directly to a digital camera to preserve the observed pictures.