Inertial profiler developer Surface Systems & Instruments, Inc. (SSI) (Auburn, California and Manhattan, Kansas, USA) is a leading supplier of pavement inspection equipment for walking, lightweight, and high speed profiling systems. SSI is a long-term user of laser based sensors for pavement measurement applications including first generation line profiling sensors introduced in 2008. These first generation sensors were specifically designed for pavement profiling applications, providing accurate measurements on challenging coarse textured pavements such as open or gap graded asphalt surfaces and tined and diamond ground concrete. These sensors increased the measurement footprint from a single point on the surface to a wide beam scanning of 4 inches (100 mm).

Although original laser line sensors provided decent profile data, the market wanted even higher density, more accurate profile data in an easier to use, more flexible, smaller sensor package. Responding to these needs, a new generation of smart 3D profile sensors was developed. The new sensors provide higher profiling rate and increased accuracy, while maintaining all of the first generation sensors’ functionalities so users can continue to use the same valuable tools they had developed within the new smart sensors.

SSI is the first manufacturer to implement the new smart sensors in high-speed inertial profilers and has received DOT (Department of Transportation) certifications. DOTs have established specific performance standards for profiling systems used in pavement inspection, particularly in repeatability and accuracy. With the new 3D smart profile sensor being used in their new inertial profiler, SSI’s goal was to exceed expectations and fully comply with the most stringent DOT requirements. A key element of an inertial profiler for measuring pavement roughness and ride quality is having an accurate, reliable 3D laser sensor. For DOTs, a 3D sensor must accurately measure all types of pavement, including all challenging coarse textured surfaces. This requirement poses a unique challenge for all profiling sensors, in that they must be able to achieve high accuracy in outdoor environments, with high data density at highway speeds, often in direct sunlight (which is a challenging environment for all optical sensors). Building on lessons learned through original sensor development, the new 3D smart profile sensor is able to handle these challenges and deliver highly accurate data.

Figure 1. Payne & Dolan Certified Inertial Profiler with Smart 3D Sensors

In preparation for the certification process, SSI installed high-speed, smart 3D sensors and inertial profiler instrumentation on a standard pickup truck platform. For SSI’s inertial profiler instrumentation, two smart sensors were installed in protective enclosures (provided by SSI), with one sensor in each wheel path. Figure 1 shows one of the sensors on Payne & Dolan’s CS9100 mid-mount configuration inertial profiler. SSI integrated sensor data with accelerometer information at each sensor, GPS data, and other vehicle sensors with a full suite of electronics for data acquisition, analysis and reporting.

Figure 2. ProVAL Certification Results

The first certification process involved the Wisconsin DOT that evaluated the system on separate asphalt and concrete test sections. The evaluation process starts with a walking device to collect a neutral survey profile on each surface, which has the wheel paths well marked with paint striping to facilitate consistent tracking of the profile devices. The candidate profiler then makes five runs on each surface. To pass the Wisconsin test, the repeated profiles from both wheel paths on each surface must correlate point-to-point at 92% for repeatability (comparing the five runs for the candidate profiler to each other) and 90% for accuracy (comparing the candidate device profiles to the neutral profile). The data was analyzed by Wisconsin DOT personnel using the “ProVAL” software program sponsored by the U.S. Federal Highway Administration. After the system test runs were completed and data was analyzed, the equipment was declared certified. Figure 2 shows the successful certification on the Wisconsin DOT longitudinally tined concrete test section.

Two SSI CS9100 systems owned by Payne & Dolan, Inc. (Waukesha, WI) and Northeast Asphalt, Inc. (Appleton, WI) passed the Wisconsin DOT certification. Subsequently, SSI inertial profiling systems with smart 3D sensors passed certification tests administered by numerous other DOTs, including California, Illinois, Kansas, Michigan, Minnesota and Texas. Figure 3 shows the passing results under Texas DOT’s certification procedure for a smart sensor equipped SSI system owned by Jobe Materials, Inc.

Figure 3. Sample TxDOT Certification Results

The new smart sensor for pavement profiling (with protective cover removed), Figure 4, includes all features of the first generation sensors, including dynamic windowing for very high speed operation, and the same selection of sensor data outputs, including full profiles over Ethernet, bridged single value, and serial interface as well as external synchronization. The smart sensor provides an easy to integrate package with the same outputs as earlier generation sensors to make updating profiling systems simple. Compared to earlier sensors, the smart 3D version features an easy to use browser based GUI, smaller package size and increased profiling speed.  Another feature of the new sensors is that all output functions are available in a single model, adding user flexibility. This is an upgrade from the original sensor, which had different models for full profile and bridged value outputs.

The new smart 3D sensors also feature a built-in web server GUI that connects to common web servers, in multiple languages, regardless of the end user operating system. This provides users with flexible simple setup, configuration and integration of critical sensor parameters such as exposure and no additional sensor controllers or PCs are needed for implementation.

Dennis Scott, President of SSI, states that cooperation with LMI was excellent in undertaking the engineering and testing to add the new 3D smart sensor to SSI’s inertial profiling systems. “We had customers that knew about the new smart sensor, and they wanted it”, said Mr. Scott. “We were fortunate to accomplish the engineering and satisfy our customers’ requests to deliver this new sensor in time for DOT certifications and profiler deployment for the 2013-2014 construction season.”

Mr. Scott confirms that several smart sensor equipped profilers are in daily use today, and the systems deliver reliable performance. For example, Brett Stanton, Quality Control Manager for Payne & Dolan, Inc. reports “We rely heavily on our new SSI systems for extensive profile testing throughout all phases of our paving projects. Our companies have two SSI smart 3D sensor equipped systems, and both have performed very well from the start.”  Alex Pinon, Field Testing Technician with Jobe Materials, Inc. agrees.  “The SSI smart sensor system has been a great upgrade for our company. We test profile on both asphalt and concrete pavements, and the new system is producing better results than our old system with spot lasers. The new system has been reliable and trouble free.”

Figure 5. Jobe Materials’ Smart Sensor Profiler

Mr. Scott states that the plan is to increasingly supply smart sensor equipped inertial profiling systems to customers worldwide.  With an already established track record or DOT certifications, acceptance for quality assurance testing in other states and provinces is assured.  SSI will also offer the enhanced performance of smart sensors as retrofit packages to owners of older profilers. The smart sensors compact design and light weight makes retrofitting to existing systems straightforward.

Multiple certifications of SSI profilers with smart sensors by many DOTs demonstrate these new 3D profiling sensors meet pavement profiling challenges. Smart 3D sensors provide accurate, higher density data on all surfaces, at highway speeds, and are not influenced by ambient light or other outdoor environmental factors.