AASHTO M 328:14(2018) Standard Specification for Inertiall Profiler.
3.1.1. accelerometer—transducer that provides an output proportional to acceleration.
3.1.2. aliasing—the error that can result when a signal is sampled at a rate less than twice the frequency of the various sinusoidal components that compose the signal. To avoid aliasing, the signal is band limited so that the sampling frequency used will be greater than twice as high as the highest frequency component in the signal. It is also described as the error that results from sampling a long wavelength signal that is mixed with a short wavelength noise signal.
3.1 .3. anti-aliasing filter—-a low-pass analog filter that suppresses short-wavelength contamination of longer-wavelength measurements to improve the accuracy of the sampling process.
3.1 .4. continuous IRI—a series of IRI values calculated over a running interval, one for each profile data point throughout the test section. Each IRI value is provided at the midpoint of the running interval.
3.1.5. filtering—-procedure to extract desired information from a signal that also contains unwanted information (commonly called noise). Digital filtering is a calculation procedure that takes one set of numbers and transforms them into another set in which the noise is reduced. Moving average is one type of such transformation or filter.
3.1.6. index—measure or standard. Within the context of this test method, a suitably chosen index quantifies the ride quality of a pavement.
3.1.7. inertial profiler— the combination of the profiling equipment and the host vehicle.
3.1 .8. international Roughness Index flRI,— a statistic used to determine the amount of roughness in a
measured longitudinal profile. The IRI is computed from a single longitudinal profile using a
quarter-car simulation at 50 mph (Sayers 1995). Computer programs to calculate the IRI from a
longitudinal profile are referenced in ASTM El926.
3.1.9. line laser—a line laser obtains a series of data points along a line, which is typically perpendicular to the travel direction, with the line typically being 4 in. long. A single, bridged elevation value is computed from this data.
3.1.10. longitudinal profile—the vertical deviations of the pavement surface taken along a line in the direction of travel referenced to a horizontal datum.
3.1.11. low-pass filter—smoot hing type filter that reduces the effect of short wavelengths that are associated with rapid elevation changes such as expansion joint ribs.
3.1.12. measurement range—the detectable range of heights, accurately measurable by the sensor.
3.1.13. moving average—filtering process whereby each data point is replaced with the average value of several adjacent points or elevations. It is a smoothing process because the changes from one elevation point to the next will not be as significant due to the fact that the difference in elevation has been divided by the total number of data points in the averaging scheme. It is a type of low- pass filter.AASHTO M 328 pdf download.