Mid-term Exam
Digital Compilation and Database Design (Fall 2004)

Answer three out of four questions.  Make sure you clearly mark which questions you answered. Your answers should be typed and double spaced and any relevant diagram neatly drawn. Please make an effort to be thorough yet concise (no more than two pages per question, not including graphics). Use all resources available to you including texts, manuals, lab exercises, and help files. The exam is due on November 2 at the beginning of class.

1. Topology of geometric objects in a GIS database defines these objects’ spatial relationships that remain invariant when they are, say stretched or bended. The violation of these spatial relationships during spatial data compilation generates topological errors. Describe 1) the topological relationships defined for Arcinfo’s coverage data model, 2) the situations when topological errors occur in a polygon coverage, 3) the global and local methods of correcting topological errors, and 4) the purposes of having topology in a GIS dataset.

2. Data normalization involves the decomposition of a large data set (i.e., table) into several small data sets and maintaining the necessary linkages between them. Describe under what circumstances normalization is required and the procedures and considerations of doing it. What are the advantages and disadvantages of building a normalized database of complex and huge datasets?

3. ArcGIS Geodatabase model uses object-oriented technology to implement spatial data models. It stores both spatial and attribute data in a single database. Describe the structure of an ArcGIS Geodatabase and how it is different from shape file or coverage data structures. Based on our lab exercises, what software features and methods are available in ArcGIS Geodatabase model to improve the GIS data integrity and accuracy? Give brief introductions on these software features and methods.

4. DEM, TIN, and contour lines are several ways of representing elevation information in a GIS database. Describe these data models and their file structures. What assumptions are used in creating these data models? What are the advantages and disadvantages of using these data models in terrain analysis?