Texture and IRI measurement with high-speed laser.
General
The Texture Laser measures the pavement texture (MPD) with a high
degree of accuracy. By combining the height information from the
texture Scanner with the Inertial Motion Unit, the International
Roughness Index (IRI) is calculated.
ViaIRI+ texture laser
The laser units contain two sensors, a laser distance meter measuring
the distance from the laser down to the road surface and a 3-axis gyro
and accelerometer used for measuring the movement of the laser unit itself.
When the car is moving and measuring, data is collected from the laser
units and stored by the PC. When the measurement is complete, the stored
data is analysed and the longitudinal profile and IRI is created, one for
each laser unit. MPD may also be calculated for each laser unit.
The ViaIRI+ consists of the following parts:
- One or more laser units placed on the front bumper of the car
- Odometer
- An interface box placed inside the car in order to collect odometer signal and to distribute power and Ethernet.
- A windows PC used for data collection and data presentation.
Longitudinal profile
The ViaIRI+ produces a longitudinal profile of the road. The profile is
intended for IRI calculations and contains wavelengths of 50 meters or less.
The profile is calculated for every 0.25 meter of the road.
IRI, International Roughness Index
ViaIRI+ calculates the IRI number from the longitudinal profile.
MPD, Mean Profile Depth
As an option, the ViaIRI+ may calculate the MPD for the road surface.
The calculation of MDP requires high speed data collection, see technical
data for more information.
Software
The ViaIRI user interface is based on the following:
- Touch screen ready. The operator can start en end measurements using
touch screen interface.
- Easy to operate. Large fonts and few numbers make it easy for the operator
to observe the measurements when the measurements are being performed.
- Background verification of measured data. The user interface checks the data
from the sensor unit ensuring that the stored data is valid.
- The user interface may also show live IRI and MPD if the IRI and/or MPD options
are selected. Notice that the live data only will give an indication of the value,
as they may differ slightly from the data calculated after the measurement. This is
due to improved filtering when the measurement is completed.
Using ViaPPS Analyzer with ViaIRI+ measurements.
All the sensor data is saved in an internal database. The report generator
produces reports in .csv or .xml format, which can be easily loaded into Microsoft Excel
for further analysis. The reports may also be provided in a custom format. The
report contains information about the date the measurement is performed, location,
system name etc. Lastly, there is a list of rows containing calculated values for a
given distance.
The Analyzer shown to the right may be used to give a graphical presentation
of the test results. This program makes it easy to analyse one measurement, or
compare several measurements. The image shows three different measurements
of longitudinal profile for the same road segment.
Technical specifications
General, sensor unit | |
Operating temperature | 0° to 40° C |
Storage temperature | -30° to 70° C |
Relative humidity | 10-90% non-condensing |
Power requirement | 12V, 48VA |
Laser | |
Laser type | Selcom 2008-180/390-A |
Laser power | 8.5mW max average |
Laser wavelength | 655 nm, (visible red) |
Safety distance | 5.6 m |
Measurement range | 180 mm |
Measurement resolution | 0.045 mm |
Maximum data rate | 32 KHz |
Sampling bandwidth | 10 KHz |
Gyro | |
Accelerometer resolution | 0.03 N |
Gyro resolution | 0.05°/sec |
Data collection | |
Laser sample rate, non MPD calculation | 8 KHz |
Laser sample rate, MPD calculation | 32 KHz |
Gyro sample rate | 200 Hz |