Geomatics inspire winter maintenance revolution
Dr. Lee Chapman, Technical Director, Entice Technology Ltd, Birmingham, UK
Dr. John E. Thornes, Reader in Applied Meteorology, University of Birmingham, UK
Countries with a marginal winter climate often face a tough decision of whether or not to treat roads for ice on a particular night. Traditionally this is achieved by using a network of road surface temperature sensors to forecast, model and monitor changes in road conditions. However, on marginal nights where the temperatures fluctuate around freezing, the presence of a few weather outstations is of limited benefit to the highway engineer. The data collected is only representative of the site under study and hence assumptions have to be made for the sections of road between sensor sites.
|Figure 1: Variation in residual road surface temperature surveyed by thermal mapping for various levels of atmospheric stability.|
Over the last couple of decades, interpolations between outstations have been made using thermal mapping surveys. By using a vehicle-mounted infrared thermometer, road surface temperatures (RST) are measured at a set spatial resolution across the road network. The magnitude of temperature variation across an area is dependent on atmospheric stability, but the actual pattern of RST variation remains similar on a nightly basis (Figure 1). For example, sections of road under bridges and in urban areas are always the warmest sections of road, regardless of weather conditions.
Thermal mapping techniques have remained largely unchanged over the past 20 years, but are now starting to show their age. Despite being costly and difficult to produce, thermal maps only provide a basic prediction of what the minimum temperature will be on the road network for five surveys at three predefined levels of atmospheric stability.
GIS, GPS and Ice-Miser
The University of Birmingham, UK, is developing a new generation of ice prediction techniques called Ice-Miser. The inspiration for a new system is a result of the proliferation of commercial "off the shelf" geomatics technology; in particular Geographical Information Systems (GIS) and Global Positioning Systems (GPS). The collection and display of spatial data has never been easier and a synergy of geomatic techniques has enabled massive innovation in road ice prediction.
|Figure 2: Fish-eye image showing a typical urban canyon. The sky-view factor is calculated by the ratio of sky pixels to non-sky pixels.|
|Figure 3: GIS screenshot showing altitude, land use and predicted road surface temperatures around a study-route in Birmingham, UK.|
Trials are constantly underway at the University of Birmingham, and early results show that Ice-Miser can consistently forecast spatial variations of RST. In a recent study, 72 percent of the variations in RST around a survey route could be explained. Also, depending on the accuracy of the meteorological forecast data, up to 95 percent of predictions were correct to within 1°C; impressive as variations of up to 13°C were present on the survey route shown in Figure 3. Away from the UK, trials are ongoing in many other countries including Japan, Slovenia, Austria and Poland.
|Figure 4: Screenshot of Ice-Miser results displayed on the Internet GIS during a trial in Slovenia.|
Based at the University of Birmingham, Entice Technology provides advice on a wide range of meteorological problems and services, including thermal surveying, environmental monitoring, salting route optimization, and ice prediction system training. For more information visit www.enticetechnology.com, or to reach Lee Chapman or John Thornes send e-mail to email@example.com.