ABSTRACT
This chapter covers transforming vector geometries with ‘unary’ and ‘binary’ operations. It also covers geometric transformations on raster objects. This involves changing the size and number of the underlying pixels, and assigning them new values. The chapter shows how raster values can be ‘masked’ and ‘extracted’ by vector geometries. It explains how to ‘polygonize’ rasters and ‘rasterize’ vector datasets, making the two data models more interchangeable. Simplification is a process for generalization of vector objects (lines and polygons) usually for use in smaller scale maps. The most commonly used centroid operation is the geographic centroid. This type of centroid operation represents the center of mass in a spatial object. Buffers are polygons representing the area within a given distance of a geometric feature: regardless of whether the input is a point, line or polygon, the output is a polygon.
