Visual Impact Assessment

Introduction

Laws and politics in scenic beauty

Need for VIA

Roles for landscape simulation

Combination of technologies

Types of visibility analysis

Traditional techniques

Local, wide area, analysis for viewpoints

Distant, close, panoramic, corridor

Mapping techniques

Projective and reflective mappings

Single and cumulative maps

Colour coded impact maps

The application of Visual Impact Assessment

Landscape simulation methods

Computer-based simulation

Hyper-linked multi-media

Criteria for good simulations

Changes due to the seasons

Applications of Visual Impact Assessment

Bernina Pass Project

Transmission towers

Lingara Bay VIA

VIA in the Forest Industry

Forestry objectives in the UK

Forest design

Visualisation tools

Simulation tool

References

Appendix

Definitions in Visual Impact Assessment

Introduction

In EIA reports the visual landscape is often described, based on its geomorphological features. Sometimes the visual impacts of the proposed development are evaluated but rarely is there a good Visualisation of the project (Lange, 1994). There are three major problems in visual landscape evaluation: the technical problem of how to visualise possible changes in the landscape; the theoretical problem of how to evaluate scenic beauty; and the administrative problem of how to integrate visual aspects in the planning process (Lange, 1994).

GIS has the capability to project 3D Visualisations of pre and post development site conditions (Selman et al, 1991). It is the integrated use, however, of several technologies, including imagery, that is best able to solve the complex Visualisation problems (Bishop and Hull, 1991). However, while the technical side of computer Visualisation is fairly advanced, the science of human-visual display interfaces is woefully inadequate (Orland and Daniel, 1995).

Regional and local issues

The Visualisation models must be reliable and generalisable, and must be able to convey their meaning to ordinary citizens. The systems should be able to accommodate detailed, fine-grained, data representations within coarse-grained data sets to support both regional and local aspects of modelling (Orland, 1992b).

Spatial, quantitative and qualitative issues

The visual impact assessment of a proposed development addresses three types of issues: spatial, quantitative and qualitative. Spatial issues include where the development is visible from or, more specifically, what or whom it is visible to; quantitative issues include how much of the development is visible, how much of the surrounding area is affected, and to what degree; and qualitative issues include the visual character of the development and its compatibility with its surroundings (Fels, 1992).

Basic functions of a VIA

Five basic functions are important in the VIA: clear identification of the various types of impacts; organisation of spatially and temporally dispersed inventory data; prediction of impacts based upon potential land use decisions; a usable interface between these functions and the planner/manager; and effective communication of potential impacts to the public and decision-makers (Bishop and Hull, 1991).

Laws and politics in scenic beauty

In Scotland, as in the rest of Britain, political and economic policies are still the major influences on decisions about locations for new industrial developments. Already, much of its lowland landscape has been intruded upon by extractive industry and urbanisation, and its highland landscape by reservoirs for both water supply and hydroelectricity (Aylward and Turnbull, 1977).

Although local government has at its disposal sophisticated planning legislation, the community is still concerned that fundamental changes may occur in the physical and visual quality of their environment and often suspects that planning and consent may be given to a development without the full disclosure of effects on the community. Thus, local government in a rural area is often motivated by pressure groups and individuals to impose stringent planning conditions which ensure that both the developers and the community are aware of the effects of the development and the alternatives available. The presentation of the evidence must be in a form that can be clearly understood and assessed by all parties (Aylward and Turnbull, 1977).

In some countries the scenery is well protected. For example in the Swiss constitution it is stated that the scenery has to be taken care of and in the case of a great interest of the general public, it has to be preserved undiminished (Lange, 1994). In the state of Wisconsin, in the USA, scenic beauty has assumed an importance in the law that currently serves as a major consideration in many of the state's regulatory functions. In 1952, the State Supreme Court ruled that the "right of the citizens of the state to enjoy our navigable streams includes the enjoyment of scenic beauty". The court held that "the occupancy (by the public) is visual" and that indeed the enjoyment of the beauty of the land constitutes a legitimate public use of land whether or not the public is allowed to set foot on it (Bishop and Hull, 1991).

The need for VIA

For natural resource managers to plan for a more healthy environment, and to elicit public and political support for such plans, two needs have been identified: (1) to predict the responses of public groups to changes in the environment, for some of which the visual impact may be the dominant indicator, and to plan to minimise any negative impacts; (2) once a proposal is developed, to communicate the effects of proposed changes to other agencies and public review groups to facilitate decision-making (Orland, 1994).

Two fundamentally different approaches for an evaluation can be distinguished: one, a professionally based approach, where the evaluation is carried out by an expert or a group of experts; the other, a publicly based approach, where the evaluation is carried out by a number of lay people representing the public or different social groups (Lange, 1994).

There have been few comprehensive programs to incorporate the Visualisation tools into environmental resource modelling systems, nor to systematically evaluate the usefulness and applicability of such systems to agency and public decision-making settings. In some areas there are comprehensive resource models, but lacking Visualisation capabilities in others there are well-developed Visualisation tools but poor links to quantitative modelling (Orland, 1992a).

Roles for landscape simulation

There are at least four kinds of roles that landscape simulation might serve in the context of landscape aesthetic policy development, implementation, and evaluation: (1) to serve as a tool for enforcement of public rights to know the aesthetic consequences of environmental modifications; (2) to create simulations which might serve as negotiated legal documents in the context of existing policies; (3) help to establish perceptually based performance standards in land use regulation; (4) assist in the assessment of monetary penalties for aesthetic damages (Bishop and Hull, 1991).

There are, of course, many methodological, substantive, and even ethical issues that will have to be resolved before the use of simulation to reinforce the public's right to know becomes commonplace: e.g. accuracy, vantage point, validity, incorporation of sounds and odours, and so on (Bishop and Hull, 1991).

Combination of technologies

Several technologies are available to assist with the modelling, inventory, interface and communication procedures to facilitate decision making about the effects of land use design, planning and management. These technologies are psychophysics, video-imaging, GIS and expert systems.

Psychophysics is a tool which assists in the assessment and prediction of scenic beauty. Video-imaging is a tool which assists in presentation of visual land use impacts to researchers, planners and the public and in the prediction of visual impacts. Expert systems are that branch of artificial intelligence research which can produce "a computer system that uses a representation of human expertise in a speciality domain in order to perform functions similar to those normally performed by a human expert in that domain" (Bishop and Hull, 1991).

GIS provides the technology for inventory of the predictor variables and consequently the scenic beauty impacts. They also provide the underlying spatial and temporal data base for inventory and prediction of the visual resource under changing land use conditions. To provide appropriate data in terms of human response, the data base must include not only the traditional physical variables but also mappings of anticipated activities and ephemeral factors (Bishop and Hull, 1991).

Used together the technologies become more than the simple sum of the parts. The use of psychophysical techniques is enhanced by the availability of video-imagery to simulate changes in the environment under controlled conditions. Prediction efforts are enhanced by expert systems which can improve upon the generalizability of results by selecting appropriate models and can make intelligent decisions regarding input data of questionable quality. The prediction models for some outcomes may not be amenable to quantitative techniques and could involve symbolic programming in the form of expert systems. The predictive models are made useful by integration with GIS or GIS and expert systems (Bishop and Hull, 1991).

Types of visibility analysis

The principle of intervisibility states that visibility is determined in two ways either from the site or to the site, that is, if point A can be seen from point B then the reverse is true. Thus although a site's visibility is normally thought of in terms of it being viewed from outside its boundaries, the outward view from the site to adjacent areas can be adopted to simplify analysis (Aylward and Turnbull, 1977).

Different types of visibility analysis include intervisibility analysis to produce levels of visual impact, dead ground analysis, identification of the portions of the landscape forming a backcloth for the design object, situations where the design object appears above the landscape horizon and the identification of optimal location for vegetation screen placement (Kennie and McLaren, 1988). The ability to map all of the viewpoints may prompt detailed interactive investigations in portions of the landscape, and suggest which portions of a planned development are most problematic and which portions might be altered to reduce visual impact (Fels, 1992). Quantifying the area visible from any location is an objective measure of the extent to which a change in land cover will be visible to an observer (Miller, 1995). Critical portions of the development can be identified, critical viewpoints can be located (Fels, 1992).

Traditional techniques

Traditional manual techniques of visibility analysis have emphasised the zone of visual intrusion associated with site development. The most important variable determining this is the terrain or landforms surrounding the site. Frequently, it is the size of the area within which the installation can be seen that is important, in other cases the critical consideration is site visibility from individual locations, such as scenic drives or picnic sites (Selman et al, 1991).

Of course determining a site's visibility does not produce the design but it can go a long way to help the speedy evaluation of alternative ideas and solutions, something that does not normally happen with more laborious and graphic simulation methods (Aylward and Turnbull, 1977). GIS-Visualisation goes beyond the simple ability to discuss single anticipated outcomes via traditional graphic tools or simple visibility analyses. It offers the opportunity to visualise relationships across time and space, and to explore more comprehensive ranges of possibility (Orland, 1994).

Local, wide area, analysis for viewpoints

An approach which uses GIS to assess resources from the perspective of recreation through evaluating scenery and visual impact has been described by Miller et al (1994). Three types of analysis are used: local analysis of scenery; wide area analysis; and analysis for viewpoints.

Local analysis of scenery uses visual impacts at particular locations and for particular scenes as well as three further factors: distance depth cueing and size perspective; angle of intersection of the view with the terrain; and land cover. The use of this method to visualise and measure the impact of forest land use change in an example scene shows that the visual impact of afforestation is generally low, being below the horizon and blending with the dark texture background of the mountains (Miller et al, 1994).

Wide area analysis uses two approaches. Viewsheds for selected visitor viewpoints are calculated to identify priority zones of visual importance to tourists. A census of the total area visible from all locations is also calculated. Analysis for viewpoints uses viewpoints to measure scenic potential by determining the number of viewpoints from which any terrain location is visible.

At present these GIS tools for the analysis of scenery are used for either historical evaluation of land use change (Gauld et al, 1991) or prediction of the impacts of future changes (Aspinall, 1990). The approach can also be linked to more traditional methods of landscape analysis, such as the use of questionnaires to assess perception of place (Miller et al, 1994).

Distant, close, panoramic, and corridor views

Four types of view can be analysed using using digital data: distant, close, panoramic and corridor (Miller, 1995).

Distant and close are terms describing a concept. They have been coined to enable scoring of the landscape with respect to observer value judgements and predict scenic value for units in which only the data on the landscape elements are known. They are views characterised by the distance of the horizon and the land immediately below the horizon, from the observer. A working definition of close may be one in which the observer can discriminate between features of interest; for example, distinguish between coniferous and deciduous trees or between woodland and heather moorland. The implications of this are that a view from the same locality, in a particular direction, may be categorised differently if the atmospheric conditions are dramatically different, and therefore accompanying a categorisation of view must be a statement of prevailing modelled conditions (Miller, 1995).

Corridors are characterised by the existence of lateral terrain features such as valley sides or woodland either side of the observer, constraining their view in a narrow field. Photographic panoramas are usually made up of a number of laterally overlapping photographs taken in a sequence around 360 degrees with the disjoins evident. In a digitally produced panorama the number of views generated can be significantly larger than those taken on the ground (Miller, 1995).

Mapping techniques

Intervisibility analysis is accomplished through many applications of viewshed mapping procedures: projective and reflective, individual and composite. The effects of temporary alterations to the topographic model can be seen and evaluated (Fels, 1992).

Projective and reflective mappings

Projective mappings are initiated from viewpoints within the development (inside looking out) while reflective mappings are initiated from viewpoints in the surrounding landscape (outside looking in). The objective of projective mapping is to reveal the extent of visibility of the development to its surroundings. The objective of reflective mapping is to determine whether, and to what extent, the development is visible from its surroundings. Reflective mapping is more similar to conventional viewshed mapping procedures than is projective mapping (Fels, 1992).

Single and cumulative mappings

Single viewpoints are useful in evaluating the effects of a specific component of the development. The use of multiple viewpoints produces composite intervisibility maps; true cumulative mapping is more useful than mapping from a predetermined set of points (Fels, 1992).

Cumulative maps portray the visibility of every point in the development with respect to every point in the landscape. f the object of study is a form of development, such as a landfill or an electrical transmission line, the study must include every model point within that landfill or along that transmission line. If the object of study is a visual resource, such as scenic river, the study must include every model point associated with that river. These maps are the most effective means for producing comprehensive appraisals of spatial and quantitative impact issues (Fels, 1992).

Colour coded impact maps

One version of such as evaluation can yield a qualitative impact, ranging, for example, from beneficial and benign to harmful and disastrous. You can produce an impact map using an evocative colour coding scheme, e.g. red for bad, green for good, yellow for neutral. (This colour scheme is by no means universal. No colour scheme is. But, as Ervin (1993) observes, within a culture of viewers used to traffic lights, it is easily understood.)

Patterns of impacts that have an element of geographic or spatial correlation (such as along drainage courses or ridge tops) became obvious in this approach and seem much more immediate when seen in pseudo-3D than when simply presented as a coloured impact map (Ervin, 1993).

The application of Visual Impact Assessments

The definition of simulation:

"an image of a proposed project shown in perspective view in the context of the actual site (Lange, 1994)."

Landscape simulation methods

A wide range of landscape simulation methods have been developed and implemented as tools for impact assessment. These include: plans, diagrams, elevations, perspective sketches, renderings, modified photographs (photo renderings and photomontages), slide projections, scale models, movies, videotapes and computer graphics (Oh, 1994). Photomontages are often used to get a subjective impression. However, it is a relatively expensive method and is restricted to fixed observer locations (Zewe and Koglin, 1995).

Computer-based simulation

Computer-based simulation methods include: two-dimensional drafting and painting; three-dimensional wire frame models; surface and solid modelling; image processing; and animation techniques. Several reports have shown successful applications of advanced computer technologies such as three-dimensional solid modelling, coloured and dynamic functions (Oh, 1994).

Another possibility is the calculation of computer graphic images by projecting aerial photographs as a texture onto landscape polygons. This method is currently being developed in France by the EDF (Électricité de France). It delivers very realistic images particularly for distant areas, but not nearby the observer (Zewe and Koglin, 1995).

Hyper-linked multi-media

Systems using hyper-linked multi-media can support a variety of investigations, proposals and evaluations that landscape planners must make, across scales, across themes and over time. A prototype hyper-media GIS system was developed for the Massachusetts Turnpike Study by Ervin (1992a) - the study contained several elements that in combination are powerful tools for landscape analysis, planning and design.

Criteria for good simulations

Lange (1994) states the following as criteria which good simulations should fulfil:

1. Representativeness - a simulation should represent important and typical views of a project.

2. Accuracy - the similarity between a simulation and the reality after the project has been realised. Of course, judging this is a little difficult beforehand.

3. Visual clarity - detail, parts and overall contents have to be clearly recognisable.

4. Interest - a simulation should hold the attention of the viewer.

5. Legitimacy - a simulation is defensible if it can be shown how it was produced and to what degree it is accurate.

Visual simulation is only descriptive; it does not release the planner from the difficult task of evaluation nor does it provide an evaluation in itself in a publicly based evaluation approach. However, visual simulation is, or at least should be, the prerequisite to predict and to evaluate the visual consequences of planned alterations (Lange, 1994).

Changes due to the seasons

There is a need to visualise change over time, using colour cues and animation. To create different simulations for the three different seasons symbols can be substituted where appropriate (bare branched deciduous trees in the winter, sparsely foliated in the spring and autumn). Fields can appear tan in the autumn and white in the winter, and bright green/yellow/blue (depending on crop) in the spring. Other dimensions of the landscape - such as visibility distances, sun and shade pockets, or "sense of enclosure" or "view of water" also change with the seasons (Ervin, 1993).

Applications of Visual Impact Assessment

Some of the cases where VIA has been used are noted below. The three assessments discussed have very different landscape types and different objectives for the studies. The Bernina Pass Project looked at the siting of a dam in an area of high scenic beauty; the transmission tower project looked at the effects of towers in several areas; and the work at Lingara Bay attempted to prevent the building of a superquarry on the island of Harris in the Outer Hebrides.

Selman et al (1991) looked at four case study sites using a GIS. Their system was found to work well for three of the four sites; Aonach Mor skiing development, powerlines in Skye, and an afforestation scheme in the Tinto Hills. The fourth site, an opencast mine, did not suit the technology used. The value of the GIS and the DTM maps produced, seem to lie principally in providing general information of alternative development layouts (Selman et al, 1991).

Bernina Pass Project

The Bernina Pass project in Switzerland looked at the location and design of a new dam. The EIA report produced was the basis for the decision of the relevant authorities, its objective was to find out whether the proposal met the criteria expressed in the various laws on environmental protection (Lange, 1994).

For the landscape simulations, Lange (1994) used a computer-aided design (CAD) software package (AUTOCAD) and an image manipulation system (PHOTOSHOP). For a dynamic simulation a DTM was produced in ARC/INFO. The digitised contour lines and the point elevation data are then transferred into a TIN and subsequently a lattice raster format.

Transmission towers

Hull and Bishop (1988) looked at the effects of electricity pylons on the landscape. The relationship between the distance from and scenic impact of pylons was examined and its functional form established. The influence of landscape type on the form was also examined, to look at its effect on shape, intercept and gradient of the equation describing the relationship between scenic impact and distance.

The study used three landscape types: rural, suburban, and flat agricultural fields. Scenes without towers were found which were very similar to scenes with towers and both sets photographed. These were then rated for `scenic beauty' using a ten point scale. The scenic impact of the transmission line was calculated by subtracting the scenic beauty estimate of the scene without the tower from that with the tower (Hull and Bishop, 1988).

Although most of the impacts were positive, there were instances where negative impacts occurred, implying that the tower had increased a scene's scenic beauty. This result is spurious, however, and probably caused by inaccurate matching of with and without tower landscape scenes. Photographic enhancement or computer simulation would enable towers to be implanted or removed from the landscape. This method would enable a perfect match and therefore a more exact estimate of scenic impact (Hull and Bishop, 1988).

Distance vs. scenic impact

Ordinary least square regression was used to determine the functional form of the relationship between distance and scenic impact. Intuition suggests that visual impact decreases as distance increases; the results showed this to be so, impact decreases rapidly as distance increases. Most of the impact occurs in the 100m to 1km range. The impact at 500m is about 25% of the maximum, by 1km it is just 10% (Hull and Bishop, 1988).

The data indicated that a tower's scenic impact is influenced by the landscape surrounding the tower. Some landscape types will contrast and make the tower stand out while others may offer camouflage. It seems that towers have less impact in more complex scenes, especially at larger distances. An explanation for this is that as distance increases, the tower becomes less of a focal point and the observer's attention is diverted by the complexity of the scene (Hull and Bishop, 1988).

Lingara Bay VIA

Scottish Natural Heritage (SNH) are opposing the development of a superquarry on the island of Harris. Their campaign has caused a majority of two thirds of the locals in favour of the project to swing to a majority of two thirds against the development (Hughes, pers. comm.).

Visibility analyses were done on the area, within a 40km radius of the bay, giving a map which showed the density of sites from which the proposed quarry was visible. A number of these sites were selected and independent visibility analyses were done on each, showing the changes in the view of the site at various time periods over the next 60 years. Panoramic photographs and line drawings were used to display the scene (Hughes, pers. comm.).

The majority of the high visibility sites were to the east of the development, on the Isle of Skye and the ferry routes between Skye and the Outer Hebrides. Shipping forecasts were used to give a reasonably accurate estimate of the amount of time that the site would be able to be seen and would not be obscured by fog, rain, or other atmospheric condition. Throughout the VIA, SNH used accurate, indisputable data, however errors still occurred due to the tolerance of the data (for example, the pixels in the DTM may have been to a resolution of 10m). This assessment gave the locals the chance to see what effect the quarry would have on their landscape and to form their own opinion based on what they had seen.

VIA in the Forest Industry

Forestry objectives in the UK

The underlying objective of commercial forestry in the UK is timber production and economics; other objectives which influence forest design include ecology, wildlife habitat, visual quality, fire and wind exposure as well as amenity and recreation (Turnbull Jeffrey Partnership, 1988). It is recognised that forests should support recreation activities and provide facilities for them but that it should still closely resemble a natural forest from a visual perspective; there should be a balance of species and age that conforms with the topography, soil type and climatic characteristics of the area (Turnbull Jeffrey Partnership, 1988).

Forest design

Visual integration of the forest with the landscape is a key element in forest design (Turnbull Jeffrey Partnership, 1988). There are seven principles of forest design (Price, 1994): naturalness, equilibrium/balance, contrast/variety, pattern, integrity, pleasantness, and honesty. These mean that there should be no straight lines or right angles. Forests should be in equilibrium and not give the impression of sliding downhill - the illusion of movement in a static landscape is a manifestation of visual forces (Turnbull Jeffrey Partnership, 1988). Changes in land use should be on the break of slope (Price, 1994) and forest-shapes superimposed on landforms should have their boundaries rise in valleys and fall on spurs, so that they respond to the shape of the ground in a direct and satisfying way (Turnbull Jeffrey Partnership, 1988).

Visualisation tools

In traditional Visualisation techniques it was very difficult to visualise the impact of the design from more than one viewpoint, or explore the dynamics of forests over time. Changes due to tree growth, harvesting and replanting couldn't be seen. It was also time consuming to transfer the perspective view of a site to a map for use by the foresters in implementing the design (Turnbull Jeffrey Partnership, 1988).

VIA tools can be used effectively in several areas of the forest design process. Decision support can be provided in the following phases of design: identifying the potential levels of visual intrusion; enabling the designer to identify the optimal location of the forest for screening purposes; locating an ideal backcloth to minimise the visual impact of buildings - the tool can locate the areas of the landscape providing this backcloth; portions of the forest that are visually exposed to the public can be identified; visual impact of objects in the landscape can be minimised if they are located to avoid their protrusion above the horizon line; identifying areas of trees that will act as screens (Turnbull Jeffrey Partnership, 1988).

Simulation tool

Turnbull Jeffrey Partnership (1988) describe CAVIA (computer-aided visual impact assessment), a predictive analysis and simulation tool that can form an integral component of a GIS. The forest design process is undertaken interactively using a graphics terminal and a digitiser. The height of block draped trees can be the thickness corresponding to tree maturity, allowing tree growth stages to be viewed. The system also provides the designer with modification tools to reshape, subdivide and delete tree blocks. The blocks are displayed as wire frame models with colour differentiating species type. The individual trees may be represented using species specific colour and symbology.

The design can be in plan or perspective and from any vantage point or direction. The system can also be used outside forestry, for example in general landscaping, power station location and electricity pylon routing (Turnbull Jeffrey Partnership, 1988).

References

Amir, S. and Gidalizon, E. (1990) Expert based Method for the Evaluation of Visual Absorption Capacity of the Landscape. Journal of Environmental Management, 30, 251-163.

Aspinall, R.J. (1990) An Integrated Approach to Land Evaluation: Grampian Region. In Evaluation of Land Resources in Scotland (eds. Bibby, J.S. and Thomas, M.F.), p45 - 56, Macaulay Land Use Research Institute and the Royal Scottish Geographical Society.

Aylward, G. and Turnbull, M. (1977) Visual analysis: a computer-aided approach to determine visibility. Computer-Aided Design, 9, 103-108.

Bishop, I.D. and Hull, R.B. (1991) Integrating technologies for visual resource management. Journal of Environmental Management, 32, 295-312.

Ervin, S.M. (1992a) A hypermedia GIS: the Massachusetts Turnpike study. Computers, Environment and Urban Systems, 16, 375-383.

Ervin, S.M. (1993) Landscape Visualisation with Emaps. IEEE Computer Graphics and Applications, 13, 28-33.

Fels, J.E. (1992) Viewshed simulation and analysis: an interactive approach. GIS World, July, 54-59.

Gauld, J.H., Bell, J.S., Towers, W. and Miller, D.R. (1991) The measurement and analysis of land cover changes in the Cairngorms. Report to the Scottish Office Environment Department and the Scottish Office Agriculture and Fisheries Department.

Hughes, R. (1995) Personal communication. Landscape and Restoration Branch, Scottish Natural Heritage, Edinburgh.

Hull, R.B. and Bishop, I.D. (1988) Scenic Impacts of Electricity Transmission Towers: The Influence of Landscape Type and Observer Distance. Journal of Environmental Management, 27, 99 - 108.

Kennie, T.J.M. and McLaren, R.A. (1988) Modelling for digital terrain and landscape Visualisation. Photogrammetric Record, 12, 711 - 745.

Lange, E. (1994) Integration of computerized visual simulation and visual assessment in environmental planning. Landscape and Urban Planning, 30, 99-112.

Miller, D.R. (1995) Categorization of terrain view. In Innovation in GIS2 (ed. Fisher, P.), chap 17, p215 - 221, Taylor and Francis.

Miller, D.R., Morrice, J.G., Horne, P.L. and Aspinall, R.J. (1994) The use of geographic information systems for analysis of scenery in the Cairngorm Mountains, Scotland. In Mountain Environments and Geographic Information Systems (eds. Price, M.F. and Heywood, D.I.), Chap 7, p119 - 131, Taylor and Francis.

Oh, K. (1994) A perceptual evaluation of computer-based landscape simulations. Landscape and Urban Planning, 28, 201-216.

Orland, B. (1992a) Data Visualisation Techniques in Environmental Management. Landscape and Urban Planning, 21, 237-244.

Orland, B. (1992b) Evaluating regional changes on the basis of local expectations: a Visualisation dilemma. Landscape and Urban Planning, 21, 257-259.

Orland, B. (1994) Visualisation techniques for incorporation in forest planning geographic information systems. Landscape and Urban Planning, 30, 83-97.

Orland, B. and Daniel, T.C. (1995) Impact of Proposed Water Withdrawls on the Perceived Scenic Beauty of Desert Springs and Wetlands: Image Generation. Imaging Systems Laboratory, Department of Landscape Architecture, University of Illinois at Urbana-Champaign.

Price, C. (1994) M.Sc. Rural Resource Management Lecture Course: Landscape. University College of North Wales, Bangor.

Pukkala, T. and Kellomaki, S. (1988) Simulation as a tool in designing forest landscape. Landscape and Urban Planning, 16, 253-260.

Selman, P., Davidson, D., Watson, A. and Winterbottom, S. (1991) GIS in rural environmental planning. Town Planning Review, 62, 215-223.

Turnbull Jeffrey Partnership (1988) Visual impact assessment in the commercial forest: design and management process.

Zewe, R. and Koglin, H.-J. (1995) A method for the visual assessment of overhead lines. Computers and Graphics, 19, 97-108.

Appendix

Definitions in Visual Impact Analysis (IEA and the Landscape Institute,1995)

Analysis (landscape): the process of breaking the landscape into its component parts to understand how it is made up.

Assessment: an umbrella term for description, analysis and evaluation.

Landscape character: distinct pattern or combination of elements that occur consistently in parts of the landscape.

Landform: combination of slope and evaluation producing the shape and form of the land surface.

Landscape evaluation: the process of attaching value (non-monetary) to a particular landscape, usually by reference to an agreed set of criteria and in the context of the assessment.

Landscape quality: term used to indicate value based on character, condition and aesthetic appeal.

Landscape resource: the combination of elements that contributes to landscape context, character and value.

Sense of place: the essential character and spirit of an area.

Visual impact: change in the appearance of the landscape as a result of development. This can be positive (improvement) or negative (detraction).

Visualisation: computer simulation, photomontage or other technique to illustrate the appearance of a development.