California Forest Highway System
Network Data Collection Project

In the Fall of 2001, the FHWA Central Federal Lands Division charged the Waterways Experiment Station Airfields and Pavements Branch of the Army Corp of Engineers (USACE-WES) with collecting data on 2,500 miles of the California Forest Highway System which consists of 134 routes covering over 2,800 miles. While driving these roads presented some of the most scenic views in California, the crew also experienced conditions which made both the collection and data analysis challenging: sheer cliffs, falling rock, hairpin turns and switchbacks, and cattle gratings. USACE-WES operated the van pictured below with one of the original PPS-2000 scanners which had been upgraded with the latest detector technology and firmware. The driver and crew of two also operated Ground Penetrating Radar and a Windshield Video and GPS system dubbed RECON developed by the Mobility Group at WES.
 
PSI accelerated the development of continuous data collection as planned for the production PPS-2002 units and invented an optimized data storage strategy to enable use of an original prototype scanner for the first network sized job tackled with a scanner . Commencing with this job, the scanner can now be operated in a mode where a run is started and runs continuously until the operator terminates the run with the keyboard
 
For this project, it was decided to collect a complete transverse scan every 2 feet and IRI in each wheel path. The raw scan data (1,000 scans per second and 4 KB/scan yielding 4 BM/sec) was double buffered in buffers holding 3 seconds of scans. The buffered data was parsed into separate output files for rut and ride. Only a complete scan every 2 feet went to the rut file while only that data necessary for ride went to the ride file. In this way the aggregate data storage requirement is just 61.3 MB/mile, resulting in a total of just over 150 GB for the project. The scanner computer was configured with two 100 GB drives permitting the full project data set to remain resident in the machine. All data was backed-up to tape as well. At a test speed of 40 mph, this data density amounts to a reduction in data to just 17% of the raw data rate.

To support USACE-WES's analysis of the data for this network, PSI evolved the scanner rut and ride software to produce statistics over a programmable distance interval, which for this project is 0.1 miles. Rut statistics include required maximum, mean and SD rut depth for each wheel path but extend to statistics for parameters that only the scanner can yield such as rut width and transverse position. While the scanner is capable of producing multiple profiles, the ride analysis required only IRI in each wheel path but for comparison the scanner software is designed to always also generate the ride index for the centerline for comparison.

To learn more about the production capabilities of PSI Scanners, call or e-mail us. The FHWA Central Federal Lands Division POC for this project is Andy Byra, and his phone number is 303.716.2137.
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