July 21, 2010

Flexible Feature Classes in ArcGIS for AutoCAD

When coaching a basketball team I really enjoy encouraging the players and seeing them improve. Kids play sports for the exercise and to have fun... it is supposed to be fun. Sometimes I would also have them listen more closely and try harder, because lets face it I want to WIN! Getting the best out of the players means a balance between challenging them (yelling) and guiding them (more yelling; perhaps with a different tone). These goals, fun and excellence don't have to be mutually exclusive. Truth is the best teams do both, they work hard listen and have more fun when they win, or at least when they are playing up to their potential.

In ArcGIS for AutoCAD a feature class is defined by filtering the entities in the drawing. An entity can belong to more than one feature class. Because of this I can have a filtering query where a feature class called WATER LINES is defined as all linear entities on the WATER LATERAL, WATER MAIN, and WATER PIPE layers. Subsets of these same entities can have their own feature classes defined with filtering criteria based solely on each of the single AutoCAD layers and or other criterion. This way when I want to work with the different kinds of pipes separately, I can.
Not only can entities have duel membership in feature classes, but because descriptive attributes are attached to the entities themselves, the feature classes can have different sets of attributes for the same entity. This means that entities can also share the same attributes honored in different feature class schema without duplication. When you want to work with the pipes as a whole you can use the feature class that includes them all. All the pipes may have the attributes of MATERIAL and DIAMETER, but perhaps only the LATERALS prompt for a STREET ADDRESS.
I can have a feature class in ArcGIS for AutoCAD that is defined as all the UTILITIES that might include the WATER, SEWER, CABLE TV and TELEPHONE. In most applications you would never want to mix the WATER and the SEWER… unless your goal was to perhaps avoid them all as in the case when you want to dig a new trench.


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