An empirical evaluation of the spatial accuracy of public participation GIS (PPGIS) data

Public participation geographic information systems (PPGIS) refers to methods that seek to integrate public knowledge of places to inform land use planning and decision making. There is little published information on the spatial accuracy of PPGIS data compared to expert-derived GIS data. This study assesses the spatial accuracy of PPGIS data collected for conservation planning in two regions of New Zealand in 2011 by comparing participant mapped locations of native vegetation with areas identified in the New Zealand Land Cover Database (LCDB) Version 2. Spatial error was operationalized as PPGIS locations having no native vegetation within 1000 m. The results indicate relatively low PPGIS spatial error of about 6% compared to 22% for randomly selected point locations in the regions. Spatial error is largest in coastal regions and near population centers where native vegetation is sparse and patchy. Participant familiarity with the study region is related to spatial error and is reflected in PPGIS sampling groups, with randomly sampled households having the largest error rate and the self-selected public, the lowest error rate. The results indicate a competitive, trade-off relationship between PPGIS participation rates and spatial accuracy. Future PPGIS research should identify processes with the capacity to increase both participation and spatial accuracy concurrently. (C) 2011 Elsevier Ltd. All rights reserved.