Towards a Data Quality Management Framework for Digital Soil Mapping
11.7 Conclusions and Perspectives
There is a structural lack of relevant soil information products at intermediate scales over wide areas. This is especially the case in regions in the world that appear as generally data scarce. To bridge this information gap methods for digital soil map-ping are required that are cheap and only require limited data input.
Although legacy soil data and related environmental data, together with cheap and easy-to-get ancillary data, provide a very useful data source for digital soil mapping they also pose data quality problems.
As is indicated in this chapter, soil data quality problems are not restricted to uncertainty issues, they also include aspects like completeness and accessibility of data. It is recognised that soil and environmental data for digital soil mapping has value in its own right, has intrinsic data quality. In addition, digital soil map-ping data must be considered in the context of the intended uses of the soil map product, highlighted by their contextual data quality. The organisation of soil and other environmental data in Soil Information Systems (Lagacherie and McBratney, 2007) can facilitate the convenience and ease of use of data, its accessibility and representational data quality (see also Kerr, 2006), for digital soil mapping.
To improve data quality in soil mapping, focus is required on quality aspects that are important to users of data. They are both soil specialists that apply existing, multi-source and multi-theme data in soil mapping, and end-users, consumers of soil information.
Existing quality management approaches in soil mapping so far merely have a producer-oriented focus and also mainly rely on inspection of end products and detection of defects. There is a need for a more user-oriented quality focus that
11 Towards a Data Quality Management Framework for Digital Soil 147 aims at the prevention of errors. This calls for a systematic approach to data quality management of the soil mapping process itself.
It is argued that elements of TDQM can assist in the development of a soil data quality management framework that focuses on the prevention of defective map-ping products as well as on increased user involvement in the generation of soil information. Issues that need further investigation in this context include:
r
The definition of a soil data quality space: which data quality dimensions are important in digital soil mapping; which ones have a more generic relevance, which ones are relevant in a particular case only.r
The development of quality metrics for the measurement of identified soil data quality dimensions. Some of them, like ‘accuracy’, will be more easy to measure, whilst for others, like ‘ease of understanding’, it will be more difficult to develop quality metrics.r
The continued development of approaches, techniques and tools for the improve-ment of the quality of soil and related environimprove-mental data; this is specifically relevant in cases where the re-use of legacy data is considered, and where the spatial and semantic integration of multi-source datasets is emphasised.It is beyond doubt that good use can be made here of the standing experience in soil mapping, such as in the application of (geo-)statistical approaches in dealing with spatial uncertainty. But also other multidisciplinary techniques and tools can be instrumental as part of a soil data quality management framework, for example elements of data mining (see for example Moran and Bui, 2002) and ontology-based semantic matching (Krol et al., 2007) that have been introduced in digital soil mapping.
The digital soil mapping community cannot leave problems with soil information products for the users to be recognised and resolved. Any team involved in digital soil mapping should pro-actively and continuously improve the quality of the soil information product. Since users are more likely to encounter problems (particularly concerning contextual data quality) with the soil information they use, as producers and/or suppliers of soil information we, therefore, need to continuously expand our knowledge about how and why our products of digital soil mapping are used.
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