Intro to GIS exam 3

Differentiate and correctly order the data models: conceptual, logical, and physical.

1. Conceptual data model — only captures important elements, and ignores minor features. (Think of a kindergarten-level map)

2. Logical data model — a map or diagram of entities modeled as features and attributes, along with the cardinal nature of any relationship. (Think of a flowchart of the entities’ relationships)

3. Physical data model — a database scheme of features, attributes, and relationships structured according to a given DBMS. (Think of a flowchart of attribute tables per entity)

Explain the meaning and components of geoprocessing.

The execution of a process on geographic data that turns raw spatial data into powerful insight.

Involves an input, process, and output.

Describe the geoprocessing framework, and its uses for automating workflow.

Geoprocessing framework — Chained geoprocessing tools, so that the same geoprocessing tool can be accessed through a script, a tool, or a model.

Use in automating workflow — can reproject all of your GIS data, and clip all of your project feature layers to a project boundary.

List common tools of vector geoprocessing.

Clip, Buffer, Intersect, Union, Dissolve, Feature to Line.

List common tools of raster geoprocessing.

Interpolation, Watershed Delineation, Contouring, Calculating Slope.

Differentiate between vector, raster, and triangulated (TIN) data.

Vector — models discrete features with precise shapes and boundaries.

Raster — focused on modeling continuous phenomena and images of the earth. Represented through discrete grid cells.

Triangulated (TIN) — focused on an efficient representation of a surface that can represent elevation or other quality. Representation is done with a series of triangles of various size.

Advantages of vector data

• Good at representing features such as rivers, states, etc.

• Points are places precisely where you need them.

• Accurate.

• Supports advanced modeling such as networks and topology.

Disadvantages of vector data

• Location of each vertex must be stored explicitly.

• Manipulation and analysis may be computer intensive for large and complex datasets.

• Cannot easily represent continous but varied geographic phenomena.

Identify the three file extensions for ArcGIS vector data.

• “.shp” — stores the shape and geometry

• “.dbf ” — stores tabular info related to the shape represented in the *.shp file

• “.shx” — file that stores the index values to connect the split files — .shp and .dbf.

Define and characterize Feature Dataset

A collection of feature classes with the same spatial reference.

Allows you to:

• thematically organize feature classes

• Enforce a common coordinate system

• Construct advanced vector networks

What is <NULL> in the table? Are they similar to 0 (zero)?

Null means “now known”. It is not similar to zero, since zero is a known value.

Define a tabular model

Nonspatial information arranged in columns and rows.

Common data formats for ArcGIS tabular data

Geodatabase, shapefile, and:

• GDB Feature Class

• GDB Table

• ESRI Shapefile

• dBase IV

• INFO

• Microsoft Excel

• Microsoft Access 2003

• Text

• Object Linking and Embedding DB

In the tabluar model, what do columns represent?

Columns are fields, they represent an attribute for a collection of entities.

In the tabular model, what do rows represent?

Rows are records, they represent attributes for each entity.

In the tabule model, what do cells represent?

Cells are values, and all values in a field are the same type (ie. text, number, data, image, etc.) (or NULL).

Compare feature class table and a standalone table. ** Which one has the geometry?

Feature Class Table:

• Has access to the feature geometry

• Every vector dataset has a feature attribute table

• Uses the feature ID to link to the feature geometry

• Has the default fields that summarize the feature geometries, such as length for line features and perimeter for polygon features.

Standalone Table:

• Does not have direct access to the feature geometry

• Does have a field linking the table to the feature attribute table whenever necessary.

• May exist as delimeted text files, dBASE files, Excel files, Access files, or files, or files managed by database software packages such as Oracle, SQL Server, and IBM DB2.

What are the four types of data relationships (cardinalities) between tables.

• one-to-one (1:1)

• one-to-many (1:M)

• many-to-one (M:1)

• many-to-many (M:M)

Explain Join vs. Relate

Join operation brings together two tables by using a key that is common to both tables

• Only two cardinalities belong to Join: one-to-one and many-to-one.

• View parent and child tables in the same window

• Query and select as one

Relate operation temporarily connects two or more tables but keeps the tables physically separate.

• Only two cardinalities belong to Relate: one-to-many & many-to-many.

• View tables in separate windows.

• Query and select separately.

Define geocoding

The process of turning a description of a location, such as its physical address, into a precise location on a map, namely, a pair of coordinates.

Uses a computer program called a “geocoding engine” that employs code tables and rules to standardize address components are carry out “fuzzy matching”.

List the steps for geocoding an address table in GIS.

1. Input table of standardized addresses.

2. Convert addresses to geospatial coordinates.

3. Map geocode records.

Three attributes of geocoding

• Status (M, U, T):

  • M = matched

  • U = unmatched

  • T = tied

• Score

• Match Type