The accuracy of map overlays

MacDougall, E. Bruce

doi:10.1016/0304-3924(75)90004-0

Cited by 69 publications

(24 citation statements)

References 2 publications

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“…Computer-assisted overlay techniques were developed some decades ago as a response to the limitations of mapping and combining large datasets by hand (MacDougall, 1975;Steinitz et al, 1976). We used this technique to combine data from a number of maps in order to prepare a set of new maps that are termed 'hazard maps' in the following.…”

Section: Methodsmentioning

confidence: 99%

Large-scale land-suitability mapping in the GIS environment for the construction site of the University Olympic Village in Izmir (Turkey)

Kıncal¹,

Koca²,

Loon³

2009

Geologos

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Participants of the 23rd University Olympic Games held in Izmir (Turkey) were hosted in a Universiade Olympic Village that had to be newly constructed. A risk analysis has been performed to assess potential engineering problems at the envisaged construction site. The risk analysis was largely based on a new, large-scale land-suitability map that was prepared in the GIS environment with much detail for this type of construction work. Information was collected from several maps, in combination with mapping in the field, drilling and seismic data. Geological, geotechnical, geophysical and morphological data were then superimposed on these analyses. This sequence of overlay analyses was performed with the help of GIS software (MapInfo Professional 7.5); this resulted in five hazard maps. Risk points (1-11) were then attributed to the different zones in the five digital hazard maps. A land-suitability map indicating the suitability for envisaged constructional activities was subsequently obtained in the form of an overlay of the five hazard maps, thus allowing to calculate a total risk for each zone on this map. The land-suitability map that was thus obtained, has been prepared for a 1:1,000 scale development plan; such a large scale is uncommon in this context.

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Section: Methodsmentioning

confidence: 99%

Large-scale land-suitability mapping in the GIS environment for the construction site of the University Olympic Village in Izmir (Turkey)

Kıncal¹,

Koca²,

Loon³

2009

Geologos

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“…It is important to realize the limitations of hand-drawn overlays. For instance, if there are more than 3 or 4 overlays, the map may appear opaque; there are accuracy questions raised by MacDougall (1975) and others that are especially pressing with handdrawn maps; and there are limitations for weighting various values represented by map units. Computer technology has helped to overcome these limitations.…”

Section: Computer Applicationsmentioning

confidence: 97%

“…This technique is used to develop the opportunities maps of step 4, the intrinsic suitability maps of step 6, and the composite map of step 7 in Table 3. MacDougall (1975) criticized the accuracy of map ovedays and made suggestions for improved accuracy. Although there has been a general tendency away from hand-drawn overlays, there are still occasions on which they may be useful.…”

Section: Computer Applicationsmentioning

confidence: 99%

Resource suitability: Methods for analyses

Steiner

1983

Environmental Management

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/ There is a growing need to develop methods for analyzing resource suitability that are both legally defensible and accurate. Three approaches to suitability analysis are reviewed: the US Soil Conservation Service capability classification and important farmlands mapping; the McHarg, or Pennsylvania, suitability analysis method; and Dutch approaches to suitability analysis. Computer applications and the carrying-capacity concept are briefly reviewed.

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“…For example, MacDougall (1975) reports that in an overlay of six maps, each with an allowable horizontal error of 0.5 mm (approximate US National Map Standards for well-defined points) and a purity of 80% (a good soils map), the possible error in the location of boundaries is 3 mm, and the purity of the overlay is 21%. On the basis of purity alone, MacDougall concluded that this overlay map is not significantly different from a random map.…”

Section: Inaccuracymentioning

confidence: 98%

“…In a thorough review of the problem, MacDougall (1975) states, "It is quite possible that overlay maps by their very nature are so inaccurate as to be useless and perhaps misleading for planning." MacDougall does not specify the level of planning to which he is referring.…”

Section: Inaccuracymentioning

confidence: 98%

Problems with using overlay mapping for planning and their implications for geographic information systems

Bailey

1988

Environmental Management

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/ As part of the planning process, maps of natural factors are often superimposed in order to identify areas which are suitable or unsuitable for a particular type of resource management. Overlay maps may also be used to identify analysis areas for predictive modeling of resource productivity and ecological response to management. Current interest in applying computer-assisted mapping technology to making overlay maps is drawing attention to geographic information systems for this purpose. The resultant maps, however, may be so inaccurate or unable to capture significant units of productivity and ecological response that they could lead to imperfect or false conclusions. Recommendations are made on how to proceed in light of these problems.An increasingly common part of the planning process for wildland areas is the preparation of map overlays to determine the suitability of an area for alternative resource management. Techniques for suitability analysis are presented in a number of papers (Varnes 1974, Larson and others 1977, Hopk]ns 1977, Ferguson 1981, FAO 19841 Steiner 1983. Maps of natural factors such as bedrock geology, soil, slope, and vegetation are superimposed in order to locate and delineate areas where particular factor combinations occur. This is done either by manually overlaying the factor maps or with an automated geographic information system (GIS). A geographic information system is a computer information system with the capability of handling spatially related data, specifically map-related data such as soil type boundaries and stream networks.An accurate overlay map would have unquestionable value in identifying types of land that will respond in a coherent and uniform way to the application of a variety of management practices. A mapping system for identifying such land types could be useful in current attempts to model the response of wildland areas. Of these models--for example, FORPLAN (Johnson and others 1986)--most utilize land types which are represented in the model by the component known as an analysis area. Because of their fundamental impor-

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The accuracy of map overlays

Cited by 69 publications

References 2 publications

Large-scale land-suitability mapping in the GIS environment for the construction site of the University Olympic Village in Izmir (Turkey)

Large-scale land-suitability mapping in the GIS environment for the construction site of the University Olympic Village in Izmir (Turkey)

Resource suitability: Methods for analyses

Problems with using overlay mapping for planning and their implications for geographic information systems

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