Forest cover change or misinterpretation? On dependent and independent vectorisation approaches
Forest cover change or misinterpretation? On dependent and independent vectorisation approaches

Summary/Abstract: The paper compares the influence of dependent and independent vectorisation approaches on forest cover change analysis, with a hypothesis that the former reduces the number and area of sliver polygons. Independent vectorisation is based on separate creation of the vector layer for each period in the time series, while the dependent is based on modification of the successive vector layers. The comparison is based on three map sets – the second Austrian military survey ( 1861/1862 ), a Polish military map ( 1936 ) and a Polish topographic map ( 1979 ) and carried out in Szczawnica commune located in the Polish Carpathians. The results show that the overall differences between the two vectorisation approaches are low at the commune level, but the local differences, within the grids 500 × 500 m might be up to 30 – 40 %. Statistical analysis did not indicate any considered variable directly responsible for the differences, confirming that it is a randomly distributed phenomenon. The results show also that the dependent vectorisation cannot eliminate the existence of sliver polygons, but their number may be limited when compared to the independent approach. As the dependent vectorisation is much more time efficient, we conclude that it might be a better solution in the situation when manual vectorisation is the most appropriate method of land use data acquisition from historical maps.

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