Abstract
The accuracy of soil survey is not well described in a consistent manner for either conventional or digital soil mapping in Queensland or more generally in Australia. Concepts of accuracy are often poorly understood and the rise of digital soil mapping has led to further terminology confusion for clients. Despite long-standing recommendations for derivation of accuracy statistics of soil surveys via statistically-based external validation, accuracy assessment by this method has been limited. Concepts for accuracy description (overall, producers and users accuracy) from the remote sensing discipline are applicable to soil survey and their use should be encouraged. An analysis of 12 published 1:50000 and 1:100000 soil surveys in Queensland revealed a 73% to 97% match between mapped polygonal and site data. This, in conjunction with accuracy standards for similar mapping disciplines and published soil survey accuracy assessments, leads us to recommend that a benchmark of 80% accuracy is realistic for all types of soil surveys. The adoption of a benchmark is however dependent upon further development and evaluation of accuracy assessment methods and standards, particularly in relation to minimum sample size and acceptance criteria. These outcomes will only be achieved if all surveys include accuracy assessment within the survey design.
Highlights
The accuracy of soil survey in Queensland or Australia in general has not been evaluated or described well, despite the existence of the profession for more than 70 years
All site and polygonal data were extracted from the Queensland Government Soil and Land Information (SALI) database and spatially joined in ArcGIS to determine the number of sites within a survey boundary that matched the dominant or subdominant SPCs of the corresponding unique mapping area (UMA)
While some progress has been made in the last 20 years, considerable effort is still required in the further development and application of consistent methods of accuracy assessment
Summary
The accuracy of soil survey in Queensland or Australia in general has not been evaluated or described well, despite the existence of the profession for more than 70 years. The use of geostatistical terminology in digital soil mapping (DSM) for reporting various model uncertainty statistics, has created further confusion for many users of soil survey data. Associated with this has been a growing paradigm that it is up to the consumer of the data to decide if it is accurate enough for their purposes. Achieving a consistent and meaningful understanding of the description and measurement of accuracy is crucial for the discipline of soil survey, both in terms of internal standards and external communication
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