SUMMARY
Transportation agencies in the United States are under intense pressure to do more with less. One of the ways in which they can increase the productivity of their staff is through the adoption of new technology. Mobile LIDAR is one of a number of new 3D technologies that offer the promise of transforming the way in which transportation agencies plan, design, construct and maintain their highway networks. This active system of measurement can be used to obtain highly accurate and dense 3D information by safely driving a collection vehicle at highway speeds.
Recognizing the potential value of this emerging and game-changing technology, the Transportation Research Board (TRB) funded this effort to develop uniform Guidelines for the use of mobile LIDAR in transportation applications. This document will assist both transportation agencies and the service provider community with the introduction and adoption of this technology by establishing a published, standard reference and common basis for understanding and communication. This will lower the risk of adoption, and potentially the costs of the technology.
This document has been organized into two main parts – Management and Technical, plus a number of Appendices that essentially document the entire research effort. In the Management section the intent is to provide guidance on the use and integration of mobile LIDAR data for a wide range of transportation applications without requiring an in-depth knowledge of the technology. For those who have the background—or want to learn more—the Technical section provides the details needed to completely specify the project requirements and deliverables.
In order to document the current state of the art, an extensive literature review was conducted. In addition all 50 DOTs responded to an online questionnaire and 14 service providers were interviewed. This establishes an important baseline by which future use and adoption can be measured. It was found that transportation agencies have a strong interest in mobile LIDAR going forward. In general there are challenges with the transition from 2D to 3D. The literature includes a number of references describing “what” is being done, but there are very few examples of best practices and/or in-depth discussions of results. Some are recognizing that mobile LIDAR—although a breakthrough technology—is not a panacea.
The foundation of the Guidelines centers on establishing the required Data Collection Categories (DCC) that is appropriate for the specific transportation application (s) of interest. The two variables considered are accuracy and point cloud density, which have been divided into nine categories of possible combinations for low, medium and high accuracy versus coarse, intermediate, and fine point cloud density.
Once the general DCC is established, the technical staff specifies both network and local accuracy in three dimensions at the 95% confidence level on a continuous scale. The density is defined as the number of LIDAR measurements per square meter required to properly define the object of interest. This approach allows managers to focus on the application(s) and the technologists on the theory and details.
It is important to note that the Guidelines are performance-based, rather than prescriptive as many other standards and specifications are. The intent is to place the responsibility for quality management on the geomatics professional in charge and to increase the longevity of the Guidelines by making them technology-agnostic. This also provides flexibility for the inevitable improvements in the technology, which in some cases are currently being pushed to the limit, while at the same time establishing a direct link between proper field procedures, documentation, deliverables and the intended end use of the data.
The Guidelines also provide general recommendations concerning the critical issue of data management. The maximum benefits of the use of mobile LIDAR will be obtained when the data is shared among departments and integrated into as many workflows as possible. There are many issues associated with managing the extremely large data sets associated with Mobile LIDAR, including interoperability and integration with existing CAD and GIS software, but a centralized data model that supports collaboration is critical to eliminating single purpose data applications.
The use of mobile LIDAR changes the survey paradigm from one where the decision making is done in the field to where it is now done in the office. Most transportation agency procurement systems are not well suited to this new methodology. It may make sense to consider the use of other procurement vehicles such as indefinite delivery, indefinite quantity contracts to better support the use of mobile LIDAR.
Finally the Guidelines address the issue of implementation. Change is never easy for an organization and it is even more challenging when it is on this scale and under these economic conditions. Actually, Mobile LIDAR is just one of the components of the technology shift that is taking place as transportation agencies transition from 2D to 3D workflows. This process is likely to extend through the current decade.
The recently enacted MAP-21 legislation as the well as the FHWA’s Every Day Counts program have identified 3D technology as transformational and something they will financially support. Introducing change of this magnitude into a complex organization such as a DOT requires vision, commitment and leadership. We trust these Guidelines support this process.