The accuracy of digital models for road design

Abstract

The paper presents majority of current methods for digital terrain models (DTM) measuring and basic requirements of traffic engineers on accuracy in the process of road design and construction. Conventional geodetic surveying methods are described as well as modern non-contact methods of the ground surface measurement, e.g. the laser scanning measurements from cars. When designing new road infrastructure, all the requirements of the environmental impact assessment imposed by the European Union must be taken into account. In connection with the application of Directive 2011/92/EU of the European Parliament saying that all newly constructed multi-lane roads must go through an intense impact on the environment (EIA analysis) and it also includes repairs of existing roads of more than 10 km length. Shortest roads may not require an EIA, but still must be built according to geometrical design standards. Calculations of the horizontal and vertical road centreline determine the three-dimensional physical location of a road considering operational, economic and environmental requirements. The density and accuracy of the DTM determine the final quality and efficiency as the design work, the quality of the geometric structure of the building. The quality and accuracy of the DTM especially determine the financial performance of the road construction. All alternative solutions are then assessed simultaneously with all the environmental and economic criteria. During reviews variants, for a first approximation with the situation, can be used DTM with less accuracy approximately 15 cm. For the design selected variant is required the accuracy of DTM around 2–3 cm. Only high quality DTM will allow us to rightly and accurately calculate the cost of road construction, to determine the exact volume of material moved and make any necessary animations and simulations. Then all simulations of transport capacity, fuel consumption and emissions will be of high quality. Only on the basis of high quality three-dimensional data it is possible to determine the horizontal and vertical axis of communication and to optimize the location of the axis, and consider operational, economic and environmental performance.