First NCDOT Mobile Scanning Projects Prove Safe, Efficient, Cost Effective

NCDOT needed design-grade pavement digital terrain models (DTMs) for design to widen five sections of interstate highway. The sections to be surveyed were all located along divided highways with high-traffic volumes.

Typically, NCDOT uses a combination of helicopter mapping and aerial photography to gather the DTM data. This requires that surveyors work along heavily traveled roadsides to place survey controls on the ground, which creates safety issues. Helicopter photogrammetry can also be costly and time consuming.

McKim & Creed offered an alternative method—mobile scanning—to capture the topographic and planimetric data NCDOT needed.

Tests Prove Mobile Scanning to be Faster, Safer, More Cost Effective

Mobile scanning combines 3-D laser scanning, GPS, inertial measurement and video technologies. Multiple scanners are mounted on an SUV or on a rail truck. These scanners collect dense and accurate 360-degree data while the vehicle travels at posted speeds. The data is used for design, modeling and simulation in 2-D, 3-D and 4-D formats.

Mobile scanning is most applicable for large transportation projects that encompass more than one mile, require normal design accuracies (less than ½-inch tolerance), have tight deadlines, involve heavily traveled or potentially dangerous areas, and can benefit from the addition of video imagery for feature collection and presentation purposes.

“We had tested mobile scanning technology as compared to traditional static scanning and knew it would be a safer, faster and less expensive way for NCDOT to get the data they needed,” recalls Tim Van Gelder, PLS, regional manager with McKim & Creed.

Working with equipment provider Terrapoint, McKim & Creed surveyed a three-mile area using static scanning, then re-scanned the area using mobile scanning, and compared the results. The tests showed that mobile scanning reduced costs by 30-40%. “Two crews worked for one week to collect the data using static scanning. With mobile scanning, the data was collected in less than half a day,” says Tony Alford, PLS, geomatics project manager with McKim & Creed.

50 Miles Scanned

Based on the results of this test scan, NCDOT agreed to implement mobile scanning technology on one project. This project was conducted along U.S. 74/76/17 from Leland to Wilmington, with the purpose of designating pavement limits and other features. Mobile scans were collected for the entire project site and supplemented with static scans every mile as a quality control measure. Survey data showing edges of pavement, travelways and curb/gutter features were extracted from the point clouds generated by the laser scanners. The data was then processed in the office, and the data was mapped and delivered to NCDOT in CAD format.

After the first project was successfully accomplished, McKim & Creed completed four additional mobile scanning projects for sections of highway near Mebane, in and around Charlotte, and in Asheville.

Railroads too?

Then NCDOT asked if McKim & Creed could mobile scan railroads. The answer from the team was, “Absolutely!”

NCDOT needed data for three sections of railroad encompassing approximately 33 miles of railway. The sections were located near Charlotte, Salisbury and Thomasville.

The McKim & Creed/Terrapoint team retrofitted the mobile scanning vehicle to NCDOT’s hi-rail truck, which traveled the project areas in at least one direction, and most in both directions to ensure full scanning coverage. The team completed the field data collection for all three projects within two days, scanning approximately 18 miles of rail per day. Mobile scanning eliminated the need for personnel on the tracks to collect survey data; therefore, no permits or rail safety classes were required.

NCDOT is pleased with the cost, safety, efficiency and quality of the data and is investigating the potential usage of mobile scanning technology for future projects.

MoDaC™ is Launched

This fall, McKim & Creed launched MoDaC™, a state-of-the-art mobile data collection system that features the Optech Lynx™ Mobile Mapper and makes McKim & Creed one of the few firms on the East Coast to offer turnkey mobile scanning services.

“We continue to see new applications for mobile scanning every day, and we knew it was time to invest in the equipment and the technology,” says Marty Stoughton, PLS, McKim & Creed’s director of business development for mobile scanning. “We believe mobile scanning is the way of the future, and we’re excited to offer a unique service to our clients that is safer, faster and more cost effective than many traditional surveying methods.”

Digital terrain modeling of pavement included edges of pavement, travelways and curbs and gutters. A 5-ft. sample grid is also shown, which was derived from the scan data and helped reveal any roadway features/contours that would have been missed if linework alone was used.

Planimetric mapping was produced showing edges of pavement, travelways, curbs and gutters, and bridge decks for the complex interchange of I-77 and I-85 in Charlotte, N.C.

McKim & Creed’s MoDaC™ mobile data collection system can collect more than 100,000 measurements per second per sensor. McKim & Creed is one of the few East Coast firms that offer turnkey mobile scanning services.

MoDaC features the Optech Lynx™ Mobile Mapper. With it, surveyors can collect data while traveling at posted speeds.