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Standard Test Method for Measuring the …

Designation: E 950 98 (Reapproved 2004) Standard Test Method forMeasuring the Longitudinal Profile of Traveled Surfaceswith an Accelerometer established inertial ProfilingReference1 This Standard is issued under the fixed designation E 950; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or This test Method covers the measurement and recordingof the profile of vehicular-traveled surfaces with an acceler-ometer established inertial reference on a The test Method uses measurement of the distancebetween an inertial plane of reference and the traveled surfacealong with the acceleration of the inertial platform to detectchanges in elevation of the surface along the length beingtraversed by the instrumented vehicle.

Designation: E 950 – 98 (Reapproved 2004) Standard Test Method for Measuring the Longitudinal Profile of Traveled Surfaces with an Accelerometer Established Inertial Profiling

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1 Designation: E 950 98 (Reapproved 2004) Standard Test Method forMeasuring the Longitudinal Profile of Traveled Surfaceswith an Accelerometer established inertial ProfilingReference1 This Standard is issued under the fixed designation E 950; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or This test Method covers the measurement and recordingof the profile of vehicular-traveled surfaces with an acceler-ometer established inertial reference on a The test Method uses measurement of the distancebetween an inertial plane of reference and the traveled surfacealong with the acceleration of the inertial platform to detectchanges in elevation of the surface along the length beingtraversed by the instrumented vehicle.

2 In order to meet aparticular class, the transducers must meet accuracy require-ments and the calculated profile must meet the specifications ofthat The values measured represent a filtered profile mea-sured from a moving plane of reference using the equipmentand procedures stated herein. The profile measurements ob-tained should agree with actual elevation measurements thatare subjected to the same filtering. Selection of proper filteringallows the user to obtain suitable wavelength information forthe intended data Either metric or inch-pound units may be used, but mustbe used consistently and not Standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this Standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to precau-tionary information is given in Referenced Standards:2E 178 Practice for Dealing with Outlying ObservationsE 867 Terminology Relating to Vehicle-Pavement SystemsE 1364 Test Method for Measuring Road Roughness byStatic Level MethodF 457 Test Method for Speed and Distance Calibration of aFifth Wheel Equipped with Either Analog or DigitalInstrumentation3.

3 In the context of this practice, the spec-trum of a digitized data record exists over the range offrequencies from zero to one half the sampling frequency. Ifthe spectrum of the original signal extends beyond one half thesampling frequency, then those components of the signal atfrequencies higher than one half the sampling frequency will,when digitized, be folded back into the spectrum of thedigitized signal. The excessively high frequency componentswill thus be aliased into low frequency filter a low-pass analog filter applied tothe original analog profile signal to suppress those componentsof the signal at frequencies higher than one half the intendeddigital sampling domain filtering a filtering operation per-formed by first calculating the the spectrum of the profilerecord and then multiplying the spectral components by thefrequency response transfer function of the record a data record of the surface elevation,slope, or acceleration.

4 Of arbitrary segment that part of a profile record for whichthe profile index will be domain filtering a filtering operation per-formed directly on the profile record1 This test Method is under the jurisdiction of ASTM Committee E17 onVehicle-Pavement Systems and is the direct responsibility of Subcommittee Methods for Measuring Profile and edition approved Dec. 1, 2004. Published December 2004. Originallyapproved in 1983. Last previous edition approved in 1998 as E 950 referenced ASTM standards, visit the ASTM website, , orcontact ASTM Customer Service at ForAnnual Book of ASTMS tandardsvolume information, refer to the Standard s Document Summary page onthe ASTM ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United Summary of Test The test apparatus consists of a vehicle equipped withthe necessary transducers, computing, and recording equip-ment to measure and record elevation profile of the traveledsurface(1).

5 The sampling rate is selected and depends on theanticipated roadway conditions and data requirements for theintended data The test apparatus is driven in the wheel tracks or in thecorrect lateral location over the section of traveled surface to beprofiled. Transducers measure vertical acceleration of thevehicle and the vertical distance between the accelerometer andthe traveled surface and the longitudinal distance. Thesetransducer signals are combined by a computer to produce thelongitudinal profile of the traveled Significance and The measurement of vehicular traveled surfaces usingan instrumented vehicle with an inertial plane of referenceprovides a satisfactory Method for acquiring traveled surfaceprofile data(1). The profile data can be processed to produce, bysimulation, the outputs of other devices. This can be done online in real time or can be computed as a post process.

6 Some ofthe devices that can be simulated include road meters(2),various straightedge devices(3), profilographs,(4), as well aspavers and grinders. Comparisons of various equipment andtheir profile computer programs are given in reference(5,6). The raw data or the profile data can also be recorded fordata processing at a later time and for analysis by morecomplex data processing The test apparatus consists of a vehicle equipped withtransducers and profile computing and recording transducers are used to measure vertical acceleration,displacement, and the distance traveled. The computer is usedto process the transducer outputs to produce the computedprofile of the traveled surface. The test apparatus must havetransducer capability for one or more tracks and a mass storagedevice for long term storage of the data. If two wheel tracks aremeasured, the displacement transducers shall be mounted m (58 to 71 in.)

7 Apart so that they measure in the twowheel tracks of the traveled surface. A set of gage blocks mustbe included to calibrate and validate static transducer opera-tion. Other supporting apparatus can include a driver speeddisplay and a graphical display of the profile or data. Someform of data display is recommended to ensure correct data isbeing Requirements The vehicle is the platform forthe mounting of the profile- Measuring equipment. The vehicleshall be large enough to accommodate all the required equip-ment without major structural modifications. The engine,steering mechanisms, and suspension components shall beadequate to allow smooth maintenance of speed and directionof travel. The environment of the interior of the vehicle shall bemaintained within tolerable limits of the instrumentation The accelerometer measures the ac-celeration used to establish the inertial reference.

8 A high-quality accelerometer shall be used that meets the classrequirements of the profiling device. The accelerometer shallbe mounted on the Measuring vehicle with the accelerometer ssensitive axis perpendicular to the traveled surface. The accel-erometer range shall be large enough to accommodate thelevels of acceleration expected from the bounce motions of themeasuring vehicle (typically61 g). The accelerometer shall bebiased to account for the 1-g acceleration of gravity. Theaccelerometer or external circuitry shall contain a self-calibration external voltage source which, on command, causesthe output of the acceleration signal level to change a prede-termined value. The accelerometer shall have a minimumresolution to allow profile calculation and accuracy and bias tomeet the class requirements as given in this Measurement A displacement trans-ducer measures the distance between the accelerometer and thetraveled surface.

9 The transducer shall be mounted on thevehicle with its Measuring axis perpendicular to the traveledsurface and in line with the sensitive axis of the displacement transducer shall measure the vertical dis-tance to the traveled surface continuously, or sample atintervals not greater than that needed to allow calculated profileas given inTable 1. The vertical resolution is that necessary tomeet the class given inTable Measurement The distance transducer maybe of the type that produces a series of pulses, the intervals ofwhich represent a distance along the traveled surface to aresolution needed to satisfyTable 1. The pulses are used tomeasure speed and can be used to convert from a function oftime to a function of distance traveled. Any distance transducerthat produces analog or digital signals with sufficient accuracymay be used. The accuracy of the distance measurement isestablished by calibration ( ).

10 Markers Use of a section start, intermedi-ate feature location(s), and section end shall be identified bylocation marks that can be accurately detected by an automaticmeans, such as magnetic detection, photocells detection ofreflective tape or similar Computation A computer shall be used toprocess acceleration, and distance transducer outputs to pro-duce measured traveled surface profile. There are two basicmethods of computing measured traveled surface Based In the spatial based Method , the trans-ducer outputs are acquired and profile data points are computedas a function of the distance traveled. In the spatial-basedmethod, the computation of measured road profile is indepen-dent of the vehicle Measuring boldface numbers in parentheses refer to the list of references at the end ofthis 1 Longitudinal SamplingClass 1less than or equal to 25 mm (1 in.)


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