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SURFACE SYSTEMS & INSTRUMENTS, INC. CS8800 WALKING PROFILER Flipbook PDF

1 S URFACE SYSTEMS & INSTRUMENTS, INC. www.smoothroad.com Custom Test Equipment • Mobile Technology Solutions CS8800

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California 501 Park Way Mill Valley, California 94941 Telephone: (415) 383-0570 Facsimile: (415) 358-4340

SURFACE SYSTEMS & INSTRUMENTS, INC.

Kansas 307 Plymate Manhattan, Kansas 66502 Telephone: (785) 539-6305 Facsimile: (415) 358-4340

www.smoothroad.com

Custom Test Equipment • Mobile Technology Solutions

CS8800 WALKING PROFILER CS8800 DATA REPEATABILITY, ACCURACY & CROSS-CORRELATION The SSI CS8800 Walking Profiler system has the proven ability to generate highly accurate and closely repeatable surface profile data. The graphs below were generated based on comparison of CS8800 walking profile data consisting of repeat data collections from the same surface. The images below report results from six same surface data collections(1) along a 541 foot (165 meter) concrete surface. (2) Four categories of performance are presented: (1) IRI Test Result Comparisons, (2) Proof of Accuracy, (3) Proof of Repeatability, and (4) Cross-Correlation of CS8800 Data. 1. Comparison of Same Surface Ride Statistics. Figure 5 shows the IRI (International Roughness Index) values for six same surface data collections with the CS8800. The IRI values are tightly clustered, with no run differing from another by more than 1.6 inches/mile on an SSI proving ground surface with a roughness content of about 215 inches per mile (3400 mm/km).

Figure 1:▲SSI CS8800 Profiling System: Same Surface IRI Comparison▲ 2. Proof of Accuracy. Figures 2 and 3 below show a comparison of same surface data from the CS8800 compared to independent survey data. The accuracy comparison shown in Figure 2 depicts an excellent pointto-point comparison between the various individual collections, with no absolute difference greater than 34 mils. Figure 3 shows a close up comparison of CS8800 data (the blue trace) overlaid on the reference survey profile with exact precision. On a running point-by-point comparison, the accumulated difference between the CS8800 system’s profile and the survey profile is 23.8 mils (0.0238 inches). This degree of accuracy exceeds the requirements of the most stringent DOT certification requirements. Prior to delivering any CS8800 profiling system to an end user, SSI’s verifies that the collection system compares against an independent reference profile with an equal or greater degree of accuracy than is required by agency specifications or equipment certification requirements.

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Figure 2:▲SSI CS8800 Profiling System Accuracy Results▲

Figure 3:▲SSI CS8800 Profiling System: Proof of Accuracy vs. Survey Data▲ 2

3. Proof of Repeatability: SSI’s CS8800 Walking Profiler system is proven to also generate highly repeatable profile data. A repeatability comparison between the six same surface CS8800 runs is shown in Figure 4. There is excellent point-to-point repeatability between the various individual collections, with a repeatability statistic of 99%

Figure 4:▲SSI CS8800 Profiling System: Repeatability of Same Surface Collections▲ 4. Cross-Correlation of CS8800 Data. An increasingly popular method of comparing same surface data from profiling devices is to compute a cross-correlation score rating the agreement between the multiple profiles. The CS8800 has demonstrated the ability for very high cross-correlation scores. Waveband correlation between six same surface data collections is shown in the table below in Figure 5. For purposes of this analysis, the wavebands of interest are: (1) IRI waveband; (2) Long (25-125 feet); (3) Medium (5-25 feet); and (4) Short (1-5 feet). Run 1

Run 2

1 1 1 1 1 2 2 2 2 3 3

2 3 4 5 6 3 4 5 6 4 5

IRI 0.994 0.994 0.98 0.983 0.991 0.994 0.981 0.981 0.99 0.984 0.984

Long 0.997 0.995 0.987 0.985 0.991 0.999 0.988 0.984 0.991 0.986 0.983 3

Waveband Medium 0.996 0.995 0.988 0.989 0.993 0.996 0.987 0.986 0.992 0.988 0.987

Short 0.965 0.977 0.891 0.882 0.946 0.957 0.885 0.856 0.932 0.902 0.905

3 6 0.99 0.989 0.992 0.954 4 5 0.997 0.998 0.997 0.983 4 6 0.991 0.991 0.993 0.955 5 6 0.991 0.99 0.993 0.954 Average 0.988333 0.990267 0.991467 0.9296 Figure 5:▲SSI CS8800 Profiling System: Cross-Correlation of Same Surface Data▲ The waveband correlation is 99% or higher in all wavebands except the short waveband, which achieved an impressive 93%. Notes: 1

Runs 4-6 were collected one day later and with a separate CS8800 device than was used to collect Runs 1-3.

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Analyses generated using a maximum 5 inch (127 mm) shift profile offset shift and 200 foot (61 m) Moving Average High Pass Filter. 3

The performance of the CS8800 and other surface profiling devices is affected by variables such as device tracking, operating speed and the magnitude of roughness and texture attributes on the test surface.

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