Scanning Areas: Line Scans, Grid Scans, and More

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Evan Mowbray

Scanning Areas: Line Scans, Grid Scans, and More

Our team at Trinity Subsurface uses a variety of tools to determine the locations of utilities and other subsurface structures. Ground penetrating radar, electromagnetic detectors, split boxes, transmitters and more can be helpful in finding potential conflicts underground. However, there’s more to locating than just having the tools: locators have to scan over the area to investigate for utilities. Today, we’ll discuss the different scanning techniques we use to locate utilities and other subsurface structures.

The most basic scan doesn’t involve tools at all. Oftentimes, utility locating may involve looking for potential access points where utilities may be accessed from above. Access points involve visible above-surface connections, such as manholes, electrical boxes, and other connections leading into structures. These access points may be barely visible from the surface and definitely won’t tell the full story compared to utilizing other scans discussed further, but they can provide a good starting point for uncovering potential utility conflicts and determining the extent of utilities and their existence within an area.

Line scans are another form of scanning used in both smaller work sites and larger areas. A line scan involves scanning in a single direction over an area multiple times using utility locating equipment. For example, our team was at a site in Philadelphia where a client was looking to install basins at multiple points within asphalt. Our team performed line scans over these areas to determine if there were utilities under the surface. Line scans can start in any direction and multiple line scans can tell a larger story of subsurface.

A grid scan can be a bit more detailed compared to a line scan, and is usually done in a single pass. The process involves scanning in a zig-zag pattern to form a grid, going over an area twice to establish a classic X and Y grid from an overhead view to create a model of the site’s subsurface infrastructure. The first X-axis scan may reveal potential utilities in an area while the additional Y-axis scan can help pinpoint utilities. From this data, further line scans can gather and confirm information within portions of the grid.

There are two types of scans that rely heavily on using a radio transmitter for the locating process. Radio transmitters are useful in amplifying the detection of utilities by producing detectable radio waves. An induction scan utilizes a transmitter connection to the utility. This usually involves attaching cables or clamps directly to surface features to get a stronger signal, detecting a specific utility line. A two-man sweep is a unique process that involves two technicians. With one technician holding an electromagnetic detector to scan and another holding a radio transmitter along the surface to produce a signal, they can walk alongside each other to detect potential utilities. On top of having another investigator investigating a line at the same time, there’s the added benefit of quicker scans.

Our team at Trinity Subsurface uses a combination of these various scanning techniques and technologies to determine the locations of underground utilities and subsurface structures, allowing for a full model of your site. Visit our website to find out more about our services and how we can locate your utilities and structures today!

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