Incorporating vegetation into visual exposure modelling in urban environments P. Bartie*, F. Reitsma, S. Kingham and S. Mills Department of Geography, University of Canterbury, Christchurch, New Zealand (Received 24 January 2010; final version received 12 July 2010) Visual exposure modelling establishes the extent to which a nominated feature may be seen from a specified location. The advent of high-resolution light detection and ranging (LiDAR)-sourced elevation models has enabled visual exposure modelling to be applied in urban regions, for example, to calculate the field of view occupied by a landmark building when observed from a nearby street. Currently, visual exposure models access a single surface elevation model to establish the lines of sight (LoSs) between the observer and the landmark feature. This is a cause for concern in vegetated areas where trees are represented as solid protrusions in the surface model totally blocking the LoSs. Additionally, the observer’s elevation, as read from the surface model, would be incor- rectly set to the tree top height in those regions. The research presented here overcomes these issues by introducing a new visual exposure model, which accesses a bare earth terrain model, to establish the observer’s true elevation even when passing through vegetated regions, a surface model for the city profile and an additional vegetation map. Where there is a difference between terrain and surface elevations, the vegetation map is consulted. In vegetated areas the LoS is permitted to continue its journey, either passing under the canopy with clear views or partially through it depending on foliage density, otherwise the LoS is terminated. This approach enables landmark visual expo- sure to be modelled more realistically, with consideration given to urban trees. The model’s improvements are demonstrated through a number of real-world trials and compared to current visual exposure methods. Keywords: visibility analysis; vegetation mapping and modelling; urban applications 1. Introduction Visibility models may be used in the planning phase of developments, for example, to calculate the visual impact of a new wind farm or to find the most hidden path for a motorway extension. They have also been used in location-based services (LBSs) to calculate what a user may see, and therefore enable context-relevant data filtering and customised content delivery (Bartie and Mackaness 2006). In all applications, model fidelity has improved as more comprehensive digital data sets have become available, yet little consideration has been given to how vegetation may be accommodated within these models. Vegetation is a special case because its impact may be seasonal, and the observer is able to see partially as well as clearly through the canopy layer. This research focuses on how a vegetation map may be incorporated into a visibility model able to report the visual exposure of nominated landmarks in urban environments. International Journal of Geographical Information Science Vol. 25, No. 5, May 2011, 851–868 *Corresponding author. Email: philbartie@gmail.com ISSN 1365-8816 print/ISSN 1362-3087 online # 2011 Taylor & Francis DOI: 10.1080/13658816.2010.512273 http://www.informaworld.com