Użyteczność danych o lasach udostępnianych w serwisie OpenStreetMap

OpenStreetMap (OSM) is a collaborative project covering the whole World with topographic data. Data are edited by volunteer users on the basis of satellite images, ortophotomaps and GPS traces, therefore are of diversified quality, especially completeness and positional accuracy. The aim of this study was to evaluate the usability of OSM forest data for Poland. We proved that positional accuracy, expressed by RMSE that equals to 16 m, was comparable with the national topographic data at the scale 1:10 000. However 3.5% of the outliers were noticed, for which the positional accuracy amounted to about 300 m. The completeness of the OSM data in May 2017, computed on the basis of Czekanowski matching feature area−based completeness index, equalled 86% and was still increasing. The lowest value of the completeness was observed for lubuskie voivodeship (76.4%), while the highest (92.5%) for zachodniopomorskie. For ten voivodeships the completeness of forest cover was greater than national average. In general, there were only a few forest polygons with their name or other pertinent characteristics like tree type (coniferous/deciduous) attributed by the editors. Logical consistency was nearly perfect as only 5.8% of the polygons were topologically incorrect. Forest definition as ‘an area dominated by trees’, is very similar in national topographic data and in OSM, both are based on physical characteristics of the surface of the Earth. Contrary to the national spatial data, OSM data are constantly updated, free and available without restrictions. It constitutes valuable alternative data source for all users. However, the heterogeneity of these data should also be kept in mind, while they are used in analysis and decision process support.