Inertial Profiler Certification for Evaluation of International Roughness Index (2018) / Chapter Skim
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From page 12... ...
12 This chapter presents background information about inertial profilers and profile data collection. The topics covered in this chapter include a description of inertial profilers, the type of height sensors used in profilers, IRI, effect of texture on data collected by inertial profilers that are equipped with different height-sensor types, reference profilers, certification of inertial profilers, network-level data collection, operational procedures for collecting profile data, and resources for information related to pavement smoothness.
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Background Information on Inertial Profilers and Profile Data Collection 13 need to have a dedicated vehicle to house the profiler, as this system can be installed in any suitable vehicle. Portable profiling systems have been popular with contractors, as they do not need a dedicated vehicle to house the profiler.
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14 Inertial Profiler Certification for Evaluation of International Roughness Index were primarily developed to measure the profile of newly placed PCC pavements, they can be used to profile both AC and PCC pavements. AASHTO Standard M 328-14, Standard Specification for Inertial Profiler (AASHTO 2017B)
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Background Information on Inertial Profilers and Profile Data Collection 15 Figure 4 shows the footprint projected by these laser types, where the footprint of the SS laser, WS laser, and the LL are shown from left to right. An SS laser projects a small dot that is typically 0.03 to 0.12 in.
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16 Inertial Profiler Certification for Evaluation of International Roughness Index laser line and then computes a single-bridged data point from this data. This strategy eliminates the problem that SS laser sensors have on longitudinally textured pavements.
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Background Information on Inertial Profilers and Profile Data Collection 17 corner (a quarter)
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18 Inertial Profiler Certification for Evaluation of International Roughness Index Profilers collect profile data along two wheelpaths (i.e., left and right wheelpaths) , and therefore, IRI values are obtained for the two wheelpaths.
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Background Information on Inertial Profilers and Profile Data Collection 19 Fernando and Walker (2013) reported a comparison of IRI values obtained from an SS laser and a RoLine laser for data collected on two types of dense-graded AC surfaces (Type C and Type D)
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20 Inertial Profiler Certification for Evaluation of International Roughness Index Perera and Karamihas (2010) reported IRI values obtained on an SMA surface by an UMTRIbuilt profiler that was equipped with an SS laser and a RoLine laser.
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Background Information on Inertial Profilers and Profile Data Collection 21 higher than that for the RoLine laser at all four sections, with the difference in IRI ranging from 1.2 to 7.5 in./mi and the average difference being 4.7 in./mi. Fernando and Walker (2013)
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22 Inertial Profiler Certification for Evaluation of International Roughness Index to the RoLine laser, with the 95% confidence interval for this difference for the Grade 3 chip seal being 3.0 to 3.3 in./mi and for the Grade 4 chip seal being 5.8 to 6.1 in./mi. Briggs (2009)
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Background Information on Inertial Profilers and Profile Data Collection 23 Fernando and Walker (2013) presented IRI values reported by a profiler manufacturer who collected data on a transversely tined PCC section in Texas with a profiler that was equipped with both an SS laser and a RoLine laser.
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24 Inertial Profiler Certification for Evaluation of International Roughness Index IRI from the profiler that was equipped with RoLine laser. The average IRI for the data from the seven profilers that had SS lasers for the left and right wheelpaths was 129 and 108 in./mi, respectively.
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Background Information on Inertial Profilers and Profile Data Collection 25 PCC surface can be very large. The difference in the magnitude of IRI for the data collected by the two laser types on such a surface could depend on groove spacing, groove width, and the groove depth.
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26 Inertial Profiler Certification for Evaluation of International Roughness Index rod-and-level data at a test section. The most important factor when collecting rod-and-level data is to make sure that the resolution of the level meets the requirements outlined in the ASTM standard.
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Background Information on Inertial Profilers and Profile Data Collection 27 the three wheels traversing the path where measurements are needed. A Panasonic Toughbook computer placed on a stand attached to the handle of the device is used to record the collected data.
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28 Inertial Profiler Certification for Evaluation of International Roughness Index with each other longitudinally and in line with the front wheel. These two wheels are in contact with the pavement surface, and the movement of these wheels is used to obtain measurements.
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Background Information on Inertial Profilers and Profile Data Collection 29 ASTM Standard E950-09 This standard was first published in 1983. The standard contains a procedure for evaluating the repeatability and accuracy of a profiler by determining the precision and the bias of a profiler.
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30 Inertial Profiler Certification for Evaluation of International Roughness Index • Procedures to perform dynamic certification testing; • Procedures to analyze the data to determine equipment repeatability and accuracy using the cross-correlation technique; • Procedures to verify the computed ride statistics (i.e., IRI) from the systems software and procedures to report results from testing; and • Procedures to test if the profile operator is qualified to operate an inertial profiler.
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Background Information on Inertial Profilers and Profile Data Collection 31 by simulating the motion of a quarter car on the profile. The filter used in the IRI algorithm to obtain the modified signal (in units of slope)
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32 Inertial Profiler Certification for Evaluation of International Roughness Index profiler 3 ft in either direction from the start, calculating the cross-correlation value at every possible offset. The maximum cross-correlation value found over the 6-ft range is the crosscorrelation value between the reference profile and the inertial profile.
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Background Information on Inertial Profilers and Profile Data Collection 33 Some state DOTs have developed their own certification procedures that include the crosscorrelation method specified in AASHTO R 56-14. The Minnesota Department of Transportation (Minnesota DOT)
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34 Inertial Profiler Certification for Evaluation of International Roughness Index distribution of IRI within a section but still have good overall agreement in IRI. This effect is illustrated in the following example: Continuous IRI plots (based on a 25-ft base length)
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Background Information on Inertial Profilers and Profile Data Collection 35 from the profiler-recorded data is compared to the IRI from the data recorded by a reference device. In the other method, the IRI from inertial profiler–recorded data is compared to data from another inertial profiler, which is considered to be the reference.
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36 Inertial Profiler Certification for Evaluation of International Roughness Index speeds are used to perform a regression analysis similar to the analysis performed for the single speed data set. For the profiler to satisfy the second criterion, A and B must fall within a specified range, and the coefficient of determination for the regression equation must be equal to or greater than 0.95.
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Background Information on Inertial Profilers and Profile Data Collection 37 For evaluating the second criterion, the overall average of the percentage difference for each 328-ft section between the profiler being evaluated and the reference inertial profiler are computed, using the following formula: ∑ ( )
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38 Inertial Profiler Certification for Evaluation of International Roughness Index For tests conducted at a constant speed, the profiler must meet the following criteria for data collected along each wheelpath to pass the accreditation test: • Difference between measured longitudinal profile and reference profile: 95% of the differences must fall within a specified range, where separate ranges are provided for the 9.8-ft and 32.8-ft wavelength data. • Cross-correlation coefficient between the measured profile and reference profile: 95% of the cross-correlation coefficient values must equal or exceed a specified value, where separate values are provided for the 9.8-ft and 32.8-ft wavelength data.
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Background Information on Inertial Profilers and Profile Data Collection 39 This standard indicates the following requirements for data collection: • Height sensors used for data collection must be separated by approximately 65 to 71 in. • Longitudinal profile data points used for calculation of IRI must have a longitudinal spacing not greater than 2 in.
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40 Inertial Profiler Certification for Evaluation of International Roughness Index • Procedure to perform the bounce test, which is an overall integrity test that checks whether the accelerometers and the height sensors in the profiler are working correctly; • Procedures to be followed during data collection, such as speed requirements, lead-in distance, and longitudinal path to profile; and • Guidelines on establishing verification sections. The operational procedures used for data collection with an inertial profiler can be divided into pre-operational tests/checks and procedures to follow during data collection.
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From page 41... ...
Background Information on Inertial Profilers and Profile Data Collection 41 data collection. Attention must be paid to the following items when collecting data with an inertial profiler: • Sensor spacing, • Operational speed, • Lead-in length, • Use of the auto-trigger, • Wet pavement, and • Debris on the pavement.
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42 Inertial Profiler Certification for Evaluation of International Roughness Index in an upward bias to the IRI values. Collecting data on damp pavement without any standing water has not shown to result in erroneous data (Evans and Eltahan 2000)
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Background Information on Inertial Profilers and Profile Data Collection 43 Texas A&M Transportation Institute (TTI) Certification Program TTI is affiliated with Texas A&M University.
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44 Inertial Profiler Certification for Evaluation of International Roughness Index The Little Book of Profiling The Little Book of Profiling (Sayers and Karamihas 1998) presents basic information about measuring and interpreting road profiles.
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