Points & Pixels

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The Bare Earth
How LIDAR in Washington state exposes geology and natural hazards

Courtesy of the Washington Geological Survey, a Division of the Washington State Department of Natural Resources (dnr.wa.gov/geology)

For geologists, LIDAR is an invaluable tool that enables them to see and study large areas of the earth’s surface, particularly in places where trees and vegetation obscure the landscape. To celebrate GIS Day, the Washington Geological Survey released a new story map titled "The Bare Earth", an incredible walk-through of how LIDAR is used to expose geology and natural hazards.

LIDAR bare-earth models allow closer study of geomorphology. Landslides, faults, floods, glaciers, and erosion leave their mark on the landscape, and while these marks can be hidden by dense vegetation, they can’t hide from LIDAR.

Special thanks to the Washington Geological Survey for this engaging and immersive tool!

Before the use of LIDAR became widespread, geologists used aerial photographs, topographic maps, and field surveys to catalog landslides. This method is problematic in much of Washington State because of the density of vegetation that often obscures features and makes field checking difficult.

Washington State has five major active volcanoes– Mount Baker, Glacier Peak, Mount Rainier, Mount Adams and Mount St. Helens. Each has erupted in the past 250 years except for Mount Adams. Repeated LIDAR surveys over time can be used to monitor volcanic activity.

Washington has dozens of active faults and fault zones. Some of these faults are in remote areas. Others, like the Seattle Fault and southern Whidbey Island fault zone, underlie major cities and pose a significant hazard. Signs of young faults include sag ponds, offset stream beds, and linear scarps. LIDAR gives geologists the ability to find these features no matter what the ground cover is like or if the feature is partly eroded.

Tsunamis are a potential threat in coastal regions of Washington. LIDAR gives scientists an accurate surface representation of the ground, and in combination with bathymetry data, allow models to more accurately predict where a tsunami could inundate an area. This modeling can give residents the ability to plan where to evacuate during an emergency. In this bare-earth LIDAR image, the contrast between the uplands and lowlands of Cape Disappointment is clearly visible.

Washington has several large glaciated peaks and mountain ranges. LIDAR can be used to monitor the growth or decline of the glaciers in these locations. Repeated monitoring over the same area documents the effects of climate change or geologic activity. Additionally, geologists can use LIDAR to discern the glacial history from the last ice age by identifying features such as moraines and outwash channels.

LIDAR is useful for many hydrologic applications in Washington. Floodplains can be mapped in detail to show where areas are at risk to flooding. Subtle river features, such as abandoned channels, ditches, terraces, and levees can be identified. This allows land managers and decision-makers to manage flood zones, preserve the natural functions of floodplains, and better craft emergency response procedures.

New AEC Industry Report Features 18 Tips for Achieving Fast, Accurate Structural Steel As-Built Models
The new report from ClearEdge3D offers 18 structural steel as-built pro tips and two case studies for taking maximum advantage of today’s automated field capture and back-office "as-built" modeling tools.

Manassas, VA — ClearEdge3D has released a new report that highlights 18 tips for optimizing project efficiency and as-built model accuracy. Scanning and modeling professionals from Allen Construction Services, Cadworks, and Hale TiP share their experiences and insights utilizing 3D laser scanning and automated modeling software tools. Two case studies examine how these tools allowed the firms to meet ultra-demanding deadlines with incredible data and model precision.

The 18 tips are organized into three categories: project management, field data capture, and project modeling/deliverables. Tips from these AEC industry professionals include:

Project Management Best Practices
Establish a data management plan that defines requirements around data processing, storage, and access. "In the beginning, we were using Dropbox to place the data," said Jake Allen, CEO of Allen Construction Services. "Someone who was not involved with the project had access to Dropbox and deleted project data files. It was a valuable lesson learned."

Field Data Capture Effeciencies
Use multiple scanners for maximum efficiency. "We achieved 2.5X field efficiency by using two scanners and 2 field staff," said Greg Hale, CTO, Hale TiP. "It’s noticeably better than simply 2X because staff can help each other use a leap frog approach for scanning and help with QC, etc." Using drones and scan targets are also mentioned for field data capture optimization.

Office Modeling & Deliverable Creation Tips
Implement a workflow that combines ClearEdge3D EdgeWiseTM software and Autodesk Revit to improve accuracy of the final model based on the software’s precise modeling algorithms and robust QA/QC tools for piping and structure. "Extraction software is more accurate than humans because we approximate too much," says Hale. "Modeling existing conditions can be very challenging. EdgeWise doubles our modeling speed and, at the same time, allows us to mitigate risks by providing accurate representations." Using ClearEdge3D VerityTM software as a model checker is also considered a back-office best practice.

"3D laser scanning has rapidly gained popularity for its automatic capture of complete as-is geometry of structures and sites," said Chris Scotton, CEO of ClearEdge3D. "Users like the ones interviewed in this report have also increasingly turned to automated software tools like EdgeWise and Verity that help them quickly convert rich laser scan point clouds into accurate as-built CAD and BIM deliverables."

This free report is available for download at http://info.clearedge3d.com/steel-report-pr

ClearEdge3D is a global technology leader in the Architectural/Engineering/Construction (AEC) industry, offering advanced software solutions that help firms model existing conditions and verify that recently completed work has been constructed correctly. The company’s EdgeWise software dramatically speeds labor-intensive 3D modeling workflows by utilizing advanced automated feature extraction and assistive modeling technology. Its Verity construction verification software compares point cloud data of recently completed work against a design or fabrication model, flagging any out-of-tolerance or poorly installed elements. For more information, please visit www.clearedge3d.com.

A 6.573Mb PDF of this article as it appeared in the magazine complete with images is available by clicking HERE