Thursday, December 3, 2015

Simple analysis in GIS

Simple analysis in GIS:

  1. Spatial measurements: GIS makes spatial measurements easy to perform. Spatial measurements can be
    1. Distance between two points
    2. The area of a polygon
    3. The length of a line or boundary.
    4. Calculations can be 
      1. of a simple nature, such as measuring areas on one map, or 
      2. complex, such as measuring overlapping areas on two or more maps. 
  2. Information Retrieval: A GIS can help point at a location, object, or area on the screen and retrieve recorded information about it from the Database Management System (DBMS) which holds the information abut the map’s features. In order for a GIS to answer the question "what is where?" we need to carry out retrieval. Retrieval is the ability of the DBMS or GIS to get back on demand data that were previously stored (Clarke, 1997). As Clarke put it "Geographic search is the secret to GIS data retrieval" so GIS systems have embedded DBMSs, or link to a commercial DBMS.
  3. Searches by attribute: Most GIS systems include a basic relational database system. All DBMS include functions for basic data display. Searches by attribute are then controlled by the capabilities of database manager. Find is the basic attribute search. Find is intended to get a single record.
  4. Searches by geography: In a map database the records are features. The GIS spatial retrieval is the generating maps, which allow searching for information visually and highlight the result. For example to generate a report; the spatial equivalent would to produce a finished map, the spatial equivalent of a find is locate. Spatial equivalents of the DBMS queries result in locating sets of features, or building new GIS layers. These include: Spatial searching, browsing the map and picking features, Spatial sorting to identify features that result from attribute sorting.Combinations of spatial and attribute queries can build some complex and powerful GIS operations. Typical GIS searches are point in polygon, line in polygon, and point distance to line.
  5. Spatial overlay: One basic way to create or identify spatial relationships is through the process of spatial overlay. Spatial overlay is accomplished by joining and viewing together separate data sets that share all or part of the same area. The result of this combination is a new data set that identifies the spatial relationships.
  6. Boundary analysis: Boundary analysis, which is referred to as districting and helps define regions according to certain criteria. This procedure is used to define area of specific demographic characteristic.  Since districting is normally an iterative process involving the development of numerous scenarios based on various combinations of desired criteria, the computing power of the GIS helps in saving time and effort. GIS helps to interactively define proposed boundaries and have related population totals automatically computed in rapidly and efficiently. 
  7. Buffer analysis: Buffer analysis is used to identify areas surrounding geographic features. The process involves generating a buffer around existing geographic features and then identifying or selecting features based on whether they fall inside or outside the boundary of the buffer.
  8. Neighborhood Operations: Neighborhood operations can evaluate the characteristics of the area surrounding a specific location. Neighborhood operations include the following: Search (Average, Diversity, Majority, Maximum/Minimum, and total), Topographic, Interpolation (interpolation involves using known cell values to predict predicting the values of intermediate cells), and Contour Generation. 
  9. Connectivity Functions: Connectivity functions involve traversing an area and accumulating values: Contiguity measures, Proximity, Network functions, Spread, Seek and Stream functions