Farmers' data for a Key Register? Assessing the spatial data quality of farmers' field geometry for use in the BGT key register for large scale topography
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In the Hoeksche Waard, the Netherlands, farmers capture geometry of crop fields in order to optimize vehicle paths for farming operations. It is investigated to what extent these farmers’ data can be used as source data in the Key Register for Large Scale Topography (BGT), a component of the Dutch national spatial data infrastructure (SDI). The use of farmers’ data for this purpose can be seen as an example of volunteered geographic information (VGI). There is an ongoing debate as to the quality of VGI, particularly in relation to SDI. There are different elements of spatial data quality, which were combined to come to an integrated assessment of the fitness of the farmers’ data for use in the BGT using a weighted sum model. The elementary scores and weights used in this model were obtained by empirical research. The empirical research consisted of two types of field work and an interview of two experts who are employed by an SDI stakeholder that is responsible for assembling the BGT for agricultural areas. The first field work involved the observation of a positional data acquisition process by farmers and the second fieldwork concerned the acquisition of positional reference data. The aim of the interview was to obtain the weights in the weighted sum model. It was found that farmers’ data meet the BGT requirements for currency and positional accuracy, but not for semantic quality. Furthermore it was found that farmers’ data are too incomplete to be used as source data in the BGT assembly, but that they can be used to report back topographic changes. To improve the fitness for use, the semantic quality of farmers’ data should be improved.