One of the many possible coordinate systems that you may encounter in GIS is called the UTM system. UTM stands for Universal Transverse Mercator, which is the most commonly used system.

These systems are called relational database management systems (RDBMS) because of their ability to form associations (relations) among the various data they contain. The data you search are contained in rows called tuples (pronounced tooples) and are grouped with corresponding rows called relations. These groupings of rows are called relations

Raster is compatible with much scanned and remotely sensed data.

You can measure connectivity in a network by comparing the number of actual node-to-node links that exist in a given network to the maximum number of nodes that are possible. This measure of connectivity is called the gamma index. Usually, the index ranges from a value of 0 (which indicates no connected links at all) to 1 (where all possible links

There are three basic types of system models for GIS: hybrid, integrated, and object-oriented. Each model type is designed to manage multiple layers.

GIS Café (www.giscafe.com): A general online GIS community that contains all things GIS, including forums, data providers, and much more. GIS Data Depot (http://data.geocomm.com): Another general online GIS community which is focused mostly on data sharing.

Much of the power of OOP data models results from the objects' shared properties, or the characteristics they have in common with other objects in their group. (I describe the sharing of properties briefly in the sidebar, "Sharing the property," and talk more about object structure in Chapter 6.) Because of shared properties, an object always knows

Raster is faster (computationally) than vector.

When you establish a relational join, all the information in the first table is shared with all the information in the second table, which is much easier than trying to make a huge, complex, comprehensive table from scratch. It's much easier to design small, individual, focused tables (that can be related to other small ones) than to create large,