You do not need to log in to the site to view the lessons. Simply click on the Teaching Units link above. Logging in is only required to edit the material. You do not need to log in to the site to view the lessons. Simply click on the Teaching Units link above. Logging in is only required to edit the material. The contiguity of neighboring pixels is not explicit in the raster data structure. However, vector data structures must explicitly determine the connectivity of the points which define an object. The space between two similar objects may be less than a pixel in width, so there will be no obvious boundary between them in a raster file. After conversion the vector based GIS will treat these two objects as a single feature. There may be multiple ways in which pixels might be connected when features are a single pixel in width or are only connected across a diagonal. Filter raster data prior to performing a conversion to vector data, so that there are no single pixel polygons or ambiguous connections between proximate features. Use a weighting scheme when converting vector maps to a raster structure so that important classes do not drop out when they cover small areas. This will unfortunately bias the area statistics of the resulting map. Select the class located at the center of each pixel location when converting from vector to raster. This will tend to maintain smaller features and will preserve overall area statistics. However, this method in no way guarantees that the label of a specific pixel corresponds to the predominant class at that location. Use line generalization functions in the GIS after converting a raster file to a vector data structure. This will reduce unnecessary points, but may also distort shapes in undesirable ways if not used with caution. Use additional data layers in the GIS to provide guidance when editing topology of features after raster-to-vector conversion (feature snapping). Source.