[PPGIS] New publication....

Greg Brown greg.brown at uq.edu.au
Thu Dec 10 14:46:30 EST 2015

Hi all,

  I have provided a link to a new publication that examines the effects of sample size on participatory mapping results with farmers in Switzerland. The purpose of the study was to assess past land use. Beni Rohrbach and colleagues investigated the data quality of participatory mapping by comparing it to reference data for past land use. Data quality indicators were completeness (55%) and correctness (67%) of participatory mapped data with ground-truthed data.  Perhaps most intriguing, they found that a rather small sample (as few as 7 participants) would have been sufficient to reach the same level of data quality as a larger sample.

The link to the article is here: http://www.landscapemap2.org/publications/rohrbach_sampling.pdf

In this article, we examine the effect of sample size on spatial data quality in participatory mapping for assessing past land use. Using a map-based questionnaire, we capture changes in the extent and location of arable farmland 20 years ago. We then compare the results of the participatory mapping with reference data from the literature and accordingly calculate quality measures based on notions of correctness and completeness. In our data, correctness is high only for areas marked by many participants; the completeness metric increases as a function of the total area delineated by the participants. These data quality metrics then are analysed for subsamples, which are computed through leave-p-out jackknifing from our sample. This cross-validation addresses the question as to whether our data would be considered correct and complete having had included fewer participants. We present evidence that a small number of participants - in our case, less than 10 - already yield high-quality data. Further, we can demonstrate that aggregating the data from those participants with highest individual data quality values does not generate the best data quality as a group. This work provides a contribution to the use of participatory mapping for gathering correct and complete data.

Greg Brown
School of Geography, Planning and Environmental Management
The University of Queensland
Email: greg.brown at uq.edu.au<mailto:greg.brown at uq.edu.au> | Ph: 07 3365 6654 | Fax: 07 3365 6899
Post: Level 4, Building 35 University of Queensland Brisbane Australia 4072

Please visit the Landscape Values and PPGIS Institute  http://www.landscapevalues.org<http://www.landscapevalues.org/>


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