Maintenance and analysis of spatial data

These functions are used to transform spatial data files, edit them and assess their accuracy.

• Format transformations - the transformation of files into the data structure and file formats used internally by the GIS
  
  
• Geometric transformations - assigning of ground coordinates to a data layer within the GIS of adjustment of one layer so it can be overlayed correctly on another data layer for the same area (the procedure is called registration)
  
  
• Conflation - the procedure of reconciling the positions of corresponding features in different data layers ie ensuring that features that have the same geographic position will coincide when two data layers are overlayed
  
  
• Edge matching and mosaicing - a procedure to adjust the position of features that extend across map sheet boundaries
  
  
• Editing functions - used to add, delete ad change the geographic position of features eg removal of sliver polygons generated during digitising or overlay operations and line snapping - extending short lines to reach features they should connect to
  
  
• Line coordinate thinning - used to reduce the quantity of coordinate data that must be stored in the GIS when more coordinates are entered than needed (Aranoff, 1989)