Using Imagery and Image Analysis Software to Manage Highway Assets
Government agencies and departments across the country face a significant challenge to manage the every-growing inventory of highway assets including painted markings, signs, and other roadway features. Creating an inventory of these assets is essential to the planning and maintenance activities that keep our roadways safe and navigable.
Like other agencies, The Maryland State Highway Administration (SHA) was challenged to find a cost-effective, accurate way to maintain their own transportation network. The State of Maryland has hundreds of thousands of road features that are distributed along a transportation network over 5,000 miles long. A critical need for the SHA was to identify all painted roadway markings and create an accurate inventory to help ensure that the painted lines were being properly maintained.
In the past, traditional field based methods to find highway markings were prohibitively expensive and time consuming. “Highway features have to be maintained and kept up to date and it is not cost effective to track highway features by driving through the state and manually tracking them,” explained Brad Davis, the GIS Liaison with the Maryland SHA Planning Department. Driving the 5,000 miles of roads across Maryland to track every highway feature is not only very costly and time consuming, but the information could become obsolete at the same rate it’s being collected.
In order to curb costs and to have a more accurate and timely inventory, the Maryland SHA elected to use aerial imagery and image analysis software from ITT (now Exelis Visual Information Solutions) to inventory painted roadway lines. Across industries, the use of aerial imagery for a variety of applications is rapidly gaining popularity as it becomes more cost efficient and more readily available. The use of imagery combined with image analysis software helps cut costs and provides an efficient means to maintain a large inventory, as with the challenge faced by the Maryland SHA Planning Department.
Imagery, particularly satellite and airborne, can help provide information about a geographic area of interest from an overall or detailed perspective. ITT’s leading image processing software, ENVI, can be used to analyze both satellite and airborne imagery to give the user additional important information about an area that can be used in reporting to colleagues and constituents, or to update a GIS for mapping purposes. New image processing and analysis technology in ENVI, includes the ability to extract specific objects of interest from an overall image scene with easy to use workflows that allow users of any skill level to easily get additional information from imagery.
Brad Davis of the Maryland SHA Planning Department was tasked with applying the new technology to the inventory of painted roadway lines across Maryland. Using aerial imagery obtained by the State of Maryland for other purposes, Davis was able to use his prior experience with satellite image processing and analysis software to identify painted roadway lines. To ensure that the information being collected was accurate, Davis employed ITT’s ENVI – the scientifically advanced image processing and analysis software that has been used for years for scientific research, and now includes automation to help anyone get useful information from an image.
One of the automated capabilities in ENVI is the feature extraction tool, which allows the user to find and select features in an image. This automated workflow allowed Davis to identify white and yellow lines painted on the road surfaces with the ease and speed needed to create an accurate inventory and keep the inventory up-to-date in a timely manner. Davis was also able to produce more results by identifying multiple types of painted lines. “By using ENVI’s feature extraction workflow I was able to identify a large amount of dashed white lines and separate them by type, resulting in a more accurate and complete inventory,” explained Davis. In the end, Davis was able to discern between white dashed and solid line markings, yellow double and single line markings, and left turn only line markings.
Once lines were extracted, he created an inventory based on that information and exported the inventory to ArcGIS, the leading software for geographic information systems or GIS from ESRI, where Davis combined the processed imagery with road centerline information in the GIS. The final product was then sent to a geodatabase and is available for utilization by the State Highway Administration, Asset Managers, and Engineers.
Through the reorientation of the methods used to manage the highway assets, applying new techniques to aerial imagery of the Maryland transportation network, and implementing an automated method to extract the location and condition of painted roadway lines, the Maryland SHA has been able to stem the costs and time required for manual maintenance inventory and has significantly increased the accuracy of their inventory.
Today, other applications for aerial and satellite imagery and image processing and analysis tools are on the horizon. Once imagery is available, advanced software can provide a wealth of information, including road shoulder widths, guardrail and sign inventory, and much more.