期刊名称：ISPRS Annals of the Photogrammetry, Remote Sensing and Spatial Information Sciences
印刷版ISSN：2194-9042
电子版ISSN：2194-9050
出版年度：2007
卷号：XXXVI-5/C55
出版社：Copernicus Publications
摘要：Much of the mobile mapping activity in Australia has been applied to the mapping of railways. Over the last decade the process has evolved from one narrowly focused upon establishing the position of track centrelines to one which includes the position and geometry of the track, imagery and detailed attributes of all trackside features. This broader perspective has been required as the mobile mapping processes have become a core requirement for the development of railway asset management systems. Positioning sensors installed on the mapping platform include GPS receivers (differential pseudo-range), shaft encoders for the measurement of travelled distance, direction sensors and tilt meters. Measurements from these sensors are taken at regular epochs and a Kalman filter is employed to integrate these and compute strings of 3D coordinates to locate the track centerline. The location of trackside features is achieved through photogrammetry, the number and configuration of the cameras being determined by the level of detail required. The preferred form of representing railway track geometry is as a continuous series of straights and curves with defined tangent points. Whilst the need for this form of geometry arises out of a business requirement for the management of the track as an asset, the representation of the track in this format has additional benefits. These include improving the accuracy of the track centreline position and providing a simple mechanism for combining a number of sets of track centreline data into a single spatial database. This paper reviews the processes used to map track centrelines and discusses the algorithms employed in reducing the coordinate strings to the required geometric format. In the horizontal plane, the string of coordinates provided by the Kalman filter is reduced to a series of straights, transition curves and circular curves. The vertical profiles are reduced to a series of straights and parabolas. The processes are essentially those of curve fitting but with added challenges of ensuring the smooth intersection of each component curve into a continuous path
