Cartographic Generalization Approach of Forestry Thematic Mapping Based on Focal Filtering
The results of forest resources planning and design survey are always presented in continuous planar patches.When the large-scale result map is reduced to the smaller-scale map,cartographic gen-eralization is often required.How to simplify the polygon boundary and keep the area and position of vari-ous objects relatively unchanged during cartography generalization is still a challenge.A large number of experiments found that the continuous planar patches was converted from vector format to raster format,then the focal majority filter was performed on the raster data in Majority manner to convert the filtered raster data to vector format for thematic mapping,which could effectively achieve cartographic generaliza-tion of forest resource thematic continuous planar feature information.This approach was used to reduce the 1∶25 000 forest inventory map to a 1∶250000 map over the 10000 hm2 study area in Yunnan.The results showed that after reduction,the polygonal boundaries were simplified,and the visual effect was good.The average absolute area change of each land use type was 0.2%,and the average positional ac-curacy was 94.68%.This approach has been widely used in the production practice of relevant thematic maps of Yunnan forest resources atlas.
NETL
NSTL
万方数据
维普
