Digital Signal Processing
Embedded Systems
Realtime Kernels
Lattice Wave Filters
Road Survey Software

This page is of historical value and what we did 1990 -- 2001.

 
 
 

 

Oberon's
Highway and Airfield Pavement Technology



Project level Pavement Measurements of
Highways and Airfields 



Airfield Measurements giving data for the
TAKEOFF application

 

 
                                                                     Targets and Objectives
  • The project level survey profilometer target is accomplished and work is planned to make it a two track network profilometer. 
  • The rapid deployment profilometer for airfields is nearly accomplished. One of its HW objectives is to have a total weight of less than ten kilos (20 lb.). 
  • We are pleased to announce that we have, repeatedly, measured profiles with up to 200 meter wavelengths. 
  •                                                              

     

      Thanks to the new DSP technology and the accuracy of lasers and accelerometers it has been possible for Oberon to put forward a system that measure, with high accuracy, longitudinal road surface properties. And this at normal traffic speeds. One of the quality requirements for Oberon's self-developed measurement system, AXON1, is to have as few self developed parts as possible, and to buy parts "over-the-shelf". This requirement makes it possible to hold the development cost low, whilst using already proven, high quality parts. Oberon integrates these hardware and software components into a system, and writes the necessary software for it. The effort needed for developing our own hardware system is thus less than in usual product development but it still exist, especially for the analogue parts. This puts us in a position where we quickly can respond to customer needs. We put this product forward, rapidly, since we saw that AXON1 is a product that fits object measurement requirements.  AXON1 is qualified by the Swedish National Road Administration, SNRA for executing object measurements (project level survey). Currently, (december 1997) there are only two companies approved. During two weeks at the end of may, 1996, AXON1 measured more than 150 times, repeatedly, fifteen road strips at different velocities. The evaluation have been be done by VTI , Road and Transport Research Institute, and resulted in a report. The qualification was divided into two parts. One part deals with measuring road networks and the other part road objects. The concept with road objects is new. An object is a stretch of road that could be newly done. The idea is to measure an object and this repeatedly over time with an high accuracy equipment. It is then possible to measure if this object do or do not comply with quality requirements set forward by SNRA. Three road properties may be qualified for object measurements: crossfall, IRI and rutdepth. Other road properties are voluntary for object measurements. A very good description of IRI and longitudinal profile is available on internet at the University of Michigan  
                      Project level measurements
    The essential difference between an project level measurement and a network measurement is that for an project level measurement the correctness and quality of all data is extremely important. The data has to be compared with forthcoming measurements of the same project. The project level measurement is thus extremely dependent on repeatability since the measurement is to be provided during a number of years. This does of course imply that the equipment has to give the same measurement response from one year to another year. It is also of great importance that the system's transducers resolution is extremely accurate. The system's calculations must also be executed with the accuracy of floating point so that software algorithms do not distort the measurement in any way, whatsoever. Network measurements are more aimed to give a statistical view of the measured network for the purpose of determining where bad road parts are located. The project level measurement is to determine a specific object's deterioration over time. Project level data is scrutinized into its smallest parts where network measurements give a country's overall view. 
    AXON1, in its current version, measure and saves longitudinal profile every five or ten centimeters, twenty meters RMS values for the profile in different wavelength bands, the international road unevenness value IRI (calculation distance twenty meters). It does also compute the new texture value (MPD) according to the ISO standard. Road longitudinal profile can show if road irregularities with long wavelengths occurs. These could be due to movement of "soil" beneath the asphalt. There are also some new ideas of measuring unevenness by investigating the power spectral density from the road's measured longitudinal profile. 
    Its measurement variables are : 
    • · IRI (international road evenness index) 
      · RMS (four values for four wavelengths) 
      · Textur (MPD) 
      · Longitudinal profile (5 cm or 10 cm) 
      · Distance (in millimeter) 

     (example of an IRI plot)  (example of a profile plot for the same road)

                  
      AXON1 is mounted in minutes on a lowered AUDI car with firmer suspension. The sensor box is not mechanically mounted with a special gadget onto the tow ball but on the car's rear transport mount (loop). 
     
     
    The main measurement device is a single SELCOM SLS5000 that measure the road surface, with the aid of some other transducers (accelerometer). The measurement data is processed, by powerful digital signal processors of the latest technology, and plotted live, graphically on a display. Not to mention the superb accelerometer. 
    Their respective resolutions are 50 micrometer, 1 micro g. In addition the wheel pulse transducer has a resolution better than 1 pulse per millimeter.