Study Guide - Notes Prior to Exam

Pages to study 14,15,18, 26, 29, 38, 47, 58, 185

Attributes - Pieces of information that describe features on a map.
Attributes include descriptive strings, coded values, discrete numeric values, real numeric values, and object identifiers.

Database schema - The structure or design of the database including relationships, organization, and compositional data.
ArcCatalog is a database schema editor.

Data Model - Abstraction or representation of the real world.
Data models are important as they determine database design.

Domain - per ESRI dictionary - The range of valid values for a particular metadata element.
This is typically in the form of a dropdown list in a geodatabase.

Feature Dataset - Multiple feature classes that participate in some sort of topological relationship.

Geodatabase - Object-relational geographic data. Provides a centralized location for storing all GIS data.

GIS Golden Rule - For every one feature of a map there is one record in the attribute table. Multi-part features do exist and are an exception to this.

Map surrounds - External features in the map layout view (legends, north arrow, scale bar, etc.).

Objects - Features (i.e. trees). Object-based data models attempt to factor in their real-world behavior. Their behavior is dependent on other objects.

Object Based Data Model - Data model including all real-world relationships.

Picture Rasters Data - A photograph used in the construction of maps (i.e. real estate advertisements).

Spectral Rasters - Usually refer to aerial orthophotography.

Subtypes - per ESRI dictionary - In geodatabases, a subset of features in a feature class or objects in a table that share the same attributes. For example, the streets in a streets feature class could be categorized into three subtypes: local streets, collector streets, and arterial streets. Creating subtypes can be more efficient than creating many feature classes or tables in a geodatabase. For example, a geodatabase with a dozen feature classes that have subtypes will perform better than a geodatabase with a hundred feature classes. Subtypes also make editing data faster and more accurate because default attribute values and domains can be set up. For example, a local street subtype could be created and defined so that whenever this type of street is added to the feature class, its speed limit attribute is automatically set to 35 miles per hour.
Subtypes are used to enhance performance

Thematic Rasters - Look at a specific phenomenon of an area (Landsat, slope).

TINs - Triangular Irregular Networks.
Display surfaces vector-based information. Creates triangles from coordinates position changes between points. TINs are a more efficient way of displaying surface information.

Topology - Spatial relationships between features
Having topology built into geodatabases speeds up spatial queries.

CGIA - Center for Geographic Information and Analysis

GSDI - Global Spatial Dataset Infrastructure

FCDC - Federal Geographic Data Committee

NCGICC - North Carolina Geographic Information Coordinating Committee
Responsible for setting standards in North Carolina.

OGC - Open Geospatial Consortium
Group working toward standardization of GIS models.

UML - Unified Modeling Language

Ways that data can be accessed in ArcGIS.
* Data access objects
* Non-topological features
* Through relational database system (i.e. Access)

Geodatabase design can be divided into 2 categories:
Logical - Our perception of geodatabase layouts. This is an interative process that all stakeholders need to be involved with design.
Physical - Actual database as realized in implementation.

Data models are moving toward increased interoperability. There is an innate problem with data portability due to the complex relationships and functionality built into data models.

Do not use spaces in file or directory names (this will eliminate a large number of errors). All data should ideally be managed within ArcCatalog in order to ensure that all data components are moved in unison. Standardized directory structures are important when dealing with larger volumes of data. File management should be a component of project design from the beginning.

We convey information through discrete objects or as raster data. Surfaces can be modeled with rasters or with TINs (triangular irregular networks).

There are a number of ways to visualize data by differentiating between attributes. Numeric data can be visualized using a number of classification schemes.

Maps exhibit spatial relationships.
* Connectivity
* Containment
* Adjacency

Layers are referenced in the map document they are not an integral component of the documents.

CAD data was the first generation data model.

Coverages are georelational data models. Multiple feature classes can be contained within a coverage, but they must be spatially related. Coverages store topology in tables. Topology was big advantage of the coverage data model. Coverages were a dominant force in GIS for 20 years. Coverages kept track of shared geometry as opposed to the coincident geometry found in geodatabases and shapefiles. Coverages cannot contain "donut" shapes or overlapping shapefiles. In coverages the "info" folder contains attributes for all features. You must use ArcCatalog to move coverages.

Shapefiles are not topological. Shapefiles must contain *.shp, *.dbf, and *.shx files. The *.shp contains the actual shape geometry, the *.dbf file is a table with all of the shape's attribute information, and the *.shx file links both of these files together. *.prj files contain the shapes relevant projection and coordinate system information. Shapefiles store single feature types that are thematic in nature. Some topological type information can be simulated through ArcGIS as the software is able to determine spatial relationships between shapefiles (this allows for queries concerning multiple shapefiles to be run). Shapefiles have limited abilities to enforce data integrity (no domains). Shapefiles do not automatically recalculate length and area.

File geodatabases are recommended over personal geodatabases. They are not stored in a conventional relational database system (Access). Personal geodatabases are limited to 2GB in size. Personal and Workgroup Scalable Geodatabases are limited to 4GB in size. File geodatabases are limited to 1TB per table (this can be expanded to 256TB). Scalabe geodatabases are capable of versioning, simultaneous editing, historical archiving, as well as check-in/check-out editing scenarios.