Introducing Geographic Information Systems with ArcGIS: A Workbook Approach to Learning GIS, 3rd Edition

A Multiplicity of “Storadigms”

ArcGIS supports, or at least recognizes, several different spatial storage paradigms:

1. File and Personal Geodatabases4

2. Shapefiles

3. Coverages

4. Computer-aided design (CAD) files

5. Vector Product Format (VPF) datasets

6. Raster (GRID) datasets

7. Triangular irregular network (TIN) datasets

8. Terrain datasets

Numbers 2, 3, 4, and 5 of these are based on the concept of the vector. We will examine and work with the first two extensively. Number 6 is the raster format already briefly discussed and covered in detail in Chapter 8. Number 7, as briefly discussed earlier, is a technique for storing data where there is an independent, continuous variable (e.g., elevation) whose values are based on the two dependent variables x and y, frequently longitude and latitude. That is, a TIN is used to represent a surface. Terrains are based on TINs covering areas with closely spaced data points.

Ideally, there would be only a single storage paradigm. We would store all spatial data in this way, and when we made a query of the database, or asked for a map of a given area and scale, it would be provided. One problem with this approach is that different sorts of data—representing different aspects of the environment—have distinctly different characteristics. Pick a point on Earth’s surface. It has elevation. If there is soil there, it has physical characteristics. Someone or some entity probably owns it. At a certain moment it has a certain temperature, ...