Is Alignment the Same as Matching ? Integration from a Cartographic Perspective

Geographic integration using overlay operations remains one of the key features of GIS and has received much attention from geographers. Integration is often presented as the universal ability to combine heterogeneous sources of data into meaningful information. While all data can be merged based on location, the significance and meaning of the resulting data is often dubious. Cartographers have paid little attention to geographic integration, but, as this paper argues, distinctions between attributes and geometry analyzed in work on automated generalization help develop approaches that can take this complexity into account. The key distinction for GIS-based geographic integration is attribute handling. Aligning accounts either explicitly or implicitly for both geometry and attributes. Matching is the operation that merges geometry and data without any consideration of attributes. The distinction between geometry and attribute is important to assure the results of merging data according to location correspond to intents and constraints. 1. TO INTEGRATE OR NOT TO INTEGRATE? What does geographic integration actually mean? This question is the starting point for this examination of how cartographic concepts can improve GIS-based geographic integration. Geographic integration using overlay operations remains one of the key features of GIS and has received much attention from geographers (Chrisman and Niemann 1985; Dangermond 1985; Flowerdew 1991; Harvey 1998; Masser 1997; Ventura 1989; Shepherd 1991) and GIS developers and users. However, most of the presentations remain superficial. In promotional materials and introductions to GIS, integration is simply an unexplained yet ubiquitous universal ability of overlay to combine heterogeneous sources of data into meaningful information based on the locational correspondence of data to the actual place (see Figures 1 and 2).