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.

Building a Geodatabase Screen Shot

Here is a screen shot from the Building a Geodatabase exercise. This screen shot show the annotation that was added to the map as part of the exercise.

Editing a Geodatabase Screen Shots

Here are a couple of screen shots from the Editing a Geodatabase exercise. The exercise involved editing networks in a geodatabase as well as working with domains and subtypes from the ArcMap interface. The first screen shot depicts some of the topological edits that were made to existing parcel dimensions.

As can be seen in the second screen shot "dimensioning" was also used.

Class 4 Notes Continued

1. Define the geodatabase.
The geodatabase (or geographic database) is similar to the ESRI coverage data model as a container in which to store data. They are three types of geodatabases used in ESRI products that can be selected for a varying data requirements. ArcGIS sotware is based around the concept of a geodatabease. The geodatabase is a more powerful data model than other alternatives offered by ESRI and allows users to form complex relationships between data as well as providing tools to streamline data entry and query construction.

2. List the elements of the geodatabase.
Some of the elements of the geodatabase include (as per the ESRI documentation)

• Annotation - A specialized feature class that stores text or graphics that provide information about features or general areas of a map. An annotation feature class may be linked to another feature class so that edits to the features are reflected in the corresponding annotation (i.e., feature-linked annotation).
• Cadastral Fabric - A cadastral fabric is a seamless parcel boundary network, which is created and maintained using data from survey records.
• Dimension - A special type of geodatabase annotation that shows specific lengths or distances on a map. A dimension feature may indicate the length of a side of a building or land parcel, or it may indicate the distance between two features such as a fire hydrant and the corner of a building.
• Feature Class - A collection of geographic features with the same geometry type (i.e., point, line, or polygon), the same attributes, and the same spatial reference. They allow homogeneous features to be grouped into a single unit for data storage purposes; for example, a feature class of city streets.
• Feature Dataset - A collection of feature classes stored together that share the same spatial reference. Feature classes in a feature dataset share a coordinate system, and their features fall within a common geographic area. Feature datasets are used to help model spatial relationships between feature classes.
• Geometric Network - Edge and junction features that represent a directed-flow system network, such as a utility or hydrologic system, in which the connectivity of features is based on their geometric coincidence.
• Network Dataset - A collection of topologically connected network elements (e.g., edges, junctions, and turns) that are derived from network sources, typically used to represent an undirected-flow system network such as a road or subway system.
• Raster Catalog- A collection of raster datasets defined in a table of any format, in which the records define the individual raster datasets that are included in the catalog. Raster catalogs can be used to display adjacent or overlapping raster datasets without having to mosaic them together in one large file.
• Raster Dataset - Any valid raster format organized into one or more bands. Each band consists of an array of pixels (cells), and each pixel has a value (e.g., a Landsat satellite image).
• Relationship Class - A class similar to relationships that exist within an RDBMS. Relationship classes manage the associations between objects in one class (e.g., table or feature class) and objects in another. Objects at either end of the relationship can be features with geometry or records in a table.
• Schematic Dataset - A dataset used for graphically representing network connectivity and sets of relationships.
• Survey Dataset - An integrated collection of specialized survey feature classes and associated survey measurements.
• Table - A set of data elements arranged in rows and columns. Each row represents a single record. Each column represents a field of the record. Tables typically store stand-alone attribute information or information associated with a spatial location such as addresses.
• Terrain - A triangulated irregular network (TIN)-based dataset that uses feature classes as data sources to model multiple resolution surfaces using z-values.
• Toolbox - A collection of dataflow and workflow processes for performing data management, analysis, and modeling.
• Topology - The arrangement that constrains how point, line, and polygon features share geometry within a geodatabase. For example, street centerlines and census blocks share geometry, and adjacent soil polygons share geometry. Topology defines and enforces data integrity rules, topological relationship queries and navigation, and sophisticated editing tools. It also allows feature construction from unstructured geometry.

3. Describe how the geodatabase is different that other spatial data formats in it's handling of 'real-world' behaviors.
The geodatabase implements several data integrity validation tools that allows the users to enforce 'real-world' behavior patterns through pre-defined 'templates'. Unlike ESRI's other available data formats 'real-world' behavior is enforced by limiting the range of potential user inputs through subtypes, domains, and default values to feature classes.

4. Describe the types of geodatabases available at 9.2.
ArcDesktop 9.2 uses three types of geodatabases, the personal, the file, and the ArcSDE geodatabase. The personal geodatabase is based on the MS Access relational database model and is limited to 2 GB of data. It is not very robust and is limited in its multiuser editing capabilities. The file geodatabase is based on a SQL relational database model and can handle up to 1 TB of data. It requires no additional software other than the ArcDesktop program. In this type of geodatabase each data set is stored in a separate file as opposed to the personal geodatabase which stores all datasets in a single *.mdb file. The file geodatabase is the recommended native format for ArcGIS. The ArcSDE geodatabase requires an additional relational geodatabase software package such as Oracle and SQL server. It is employed for enterprise solutions and its upper limits are dependent on the software package upon which it is based.