Geographic Information Systems GIS SGO1910

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Geographic Information Systems (GIS)SGO1910
SGO4930 Fall 2005
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Revised Schedule

• Week 43 (October 25) Geographic
  Databases Chapters 10
• Week 44 (Nov. 1) Geographic Analysis Chapters 14,
  15
• Week 45 (Nov. 8) Mid-term Quiz II
• Map Production Chapter 12
• Week 46 (Nov. 15) GIS and Society Chapter 18
• Week 47 (November 22) NO CLASS
• Week 48 Final Exam Dec 1

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Oslo Project

• The aim of this project is to integrate what you
  have learned in GIS lectures and labs through
  practical experience. Working in groups of three
  or four, you will address a spatial issue in Oslo
  (e.g. resource distribution, inequality) through
  the collection, mapping and analysis of data,
  which will then be presented in a concise
  professional report that is no more than 12 pages
  long, including maps and references.

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Groups

• You may select your own group, or we can create
  groups for you. Groups should be established this
  week in lab please email me the members of your
  group.
• Graduate students have the option of doing an
  independent project related to their own
  research, or the Oslo project in a group.

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New Textbook??

• GIS - Geographic Information Systems for the
  Social Sciences Investigating Space and Place
  (Steinbergy, S.J. and Steinberg, S.L. 2005. Sage
  Publications)
• Replace Longley et al.? Supplement it?

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Geographic Databases
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A GIS can answer the question What is where?

• WHAT Characteristics of attributes or features.
• WHERE In geographic space.

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A GIS links attribute and spatial data

• Attribute Data
• Flat File
• Relations

• Map Data
• Point File
• Line File
• Area File
• Topology

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Flat File Database
Attribute
Attribute
Attribute
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Arc/node map data structure with files
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1 x y
11
e
2 x y
l
i
12
3 x y
F

10
2
s
4 x y
t
7
n
5 x y
i
5
o
POLYGON A
6 x y
P
9
7 x y
4
8 x y
6
1
9 x y
2
10 x y
3
11 x y
8
12 x y
13 x y
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File of Arcs by Polygon
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1,2,3,4,5,6,7
A
1,2
, Area, Attributes
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1,8,9,10,11,12,13,7
Arcs File
Figure 3.4
Arc/Node Map Data Structure with Files.
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What is a Data Model?

• A logical construct for the storage and retrieval
  of information.
• Attribute data models are needed for the DBMS.
• The origin of DBMS data models is in computer
  science.

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Definitions

• Database an integrated set of data on a
  particular subject
• Geographic (spatial) database - database
  containing geographic data of a particular
  subject for a particular area
• Database Management System (DBMS) software to
  create, maintain and access databases

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A DBMS contains

• Data definition language
• Data dictionary
• Data-entry module
• Data update module
• Report generator
• Query language

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Advantages of Databases

• Avoids redundancy and duplication
• Reduces data maintenance costs
• Applications are separated from the data
• Applications persist over time
• Support multiple concurrent applications
• Better data sharing
• Security and standards can be defined and
  enforced

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Disadvantages of Databases

• Expense
• Complexity
• Performance especially complex data types
• Integration with other systems can be difficult

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Characteristics of DBMS (1)

• Data model support for multiple data types
• e.g MS Access supports Text, Memo, Number,
  Date/Time, Currency, AutoNumber, Yes/No, OLE
  Object, Hyperlink, Lookup Wizard
• Load data from files, databases and other
  applications
• Index for rapid retrieval

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Characteristics of DBMS (2)

• Query language SQL
• Security controlled access to data
• Multi-level groups
• Controlled update using a transaction manager
• Backup and recovery

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Role of DBMS
Task
System

• Data load
• Editing
• Visualization
• Mapping
• Analysis

Geographic Information System

• Storage
• Indexing
• Security
• Query

Database Management System
Data
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Retrieval

• The ability of the DBMS or GIS to get back on
  demand data that were previously stored.
• Geographic search is the secret to GIS data
  retrieval.
• Many forms of data organization are incapable of
  geographic search.
• GIS systems have embedded DBMSs, or link to a
  commercial DBMS.

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Types of DBMS Model

• Hierarchical
• Network
• Relational - RDBMS
• Object-oriented - OODBMS
• Object-relational - ORDBMS

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Historically, databases were structured
hierarchically in files...
Norge
Akershus
Oppland
Hordaland
Asker
Bærum
Ski
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Relational DBMS

• Data stored as tuples (tup-el), conceptualized as
  tables
• Table data about a class of objects
• Two-dimensional list (array)
• Rows objects
• Columns object states (properties, attributes)

Tuple??? A row in a relational table synonymous
with record, observation. A set of elements.
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Relation Rules

• Only one value in each cell (intersection of row
  and column)
• All values in a column are about the same subject
• Each row is unique
• No significance in column sequence
• No significance in row sequence

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Table
Column property
Table Object Class
Row object
Object Classes with Geometry called Feature
Classes
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Relational Join

• Fundamental query operation
• Table joins use common keys (column values)
• Table (attribute) join concept has been extended
  to geographic case

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Relational Data Bases
File
Patient Record
Key Check-in
Check Out
Room No.
42
2/1/96
2/4/96
N763
78
2/3/96
2/4/96
N712
Purchase Record
File
Item
Date
Price
Customer
Key
Skate Board
2/1/96
49.95
John Smith
42
Baseball Bat
2/1/96
17.99
James Brown
978
File
Accident Report
Date
Injury
Name
Key
Location
2/1/96
Broken Leg
John Smith
42
75 Elm Street
2/2/96
Concussion
Sylvia Jones
654
12 State Street
2/2/96
Cut on Ear
Robert Doe
123
2323 Broad Street
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Most DBMS are now relational databases.

• Based on multiple flat files for records, with
  dissimilar attribute structures, connected by a
  common key attribute.

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Retrieval Operations

• Searches by attribute find and browse.
• Data reorganization select, renumber, and sort.
• Compute allows the creation of new attributes
  based on calculated values.

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Spatial Retrieval Operations

• Attribute queries are not very useful for
  geographic search.
• In a map database the records are features.
• The spatial equivalent of a find is locate, the
  GIS highlights the result.
• Spatial equivalents of the DBMS queries result
  in locating sets of features or building new GIS
  layers.

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The Retrieval User Interface

• GIS query is usually by command line, batch, or
  macro.
• Most GIS packages use the GUI of the computers
  operating system to support both a menu-type
  query interface and a macro or programming
  language.
• SQL is a standard interface to relational
  databases and is supported by many GISs.

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SQL

• Structured (Standard) Query Language
  (pronounced SEQUEL)
• Developed by IBM in 1970s
• Now de facto and de jure standard for accessing
  relational databases
• Three types of usage
• Stand alone queries
• High level programming
• Embedded in other applications

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Types of SQL Statements

• Data Definition Language (DDL)
• Create, alter and delete data
• CREATE TABLE, CREATE INDEX
• Data Manipulation Language (DML)
• Retrieve and manipulate data
• SELECT, UPDATE, DELETE, INSERT
• Data Control Languages (DCL)
• Control security of data
• GRANT, CREATE USER, DROP USER

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Spatial Relations

• Equals same geometries
• Disjoint geometries share common point
• Intersects geometries intersect
• Touches geometries intersect at common boundary
• Crosses geometries overlap
• Within geometry within
• Contains geometry completely contains
• Overlaps geometries of same dimension overlap
• Relate intersection between interior, boundary
  or exterior

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Spatial Methods

• Distance shortest distance
• Buffer geometric buffer
• ConvexHull smallest convex polygon geometry
• Intersection points common to two geometries
• Union all points in geometries
• Difference points different between two
  geometries
• SymDifference points in either, but not both of
  input geometries

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Spatial Search

• Buffering is a spatial retrieval around points,
  lines, or areas based on distance.
• Overlay is a spatial retrieval operation that is
  equivalent to an attribute join.

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Identify
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Recode
OR
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Data overlay
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Overlay
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Types of overlay operations

• And
• Or
• Max
• Min

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Buffer (raster)
1
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Buffer (vector)
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Complex Retrieval Map Algebra

• Combinations of spatial and attribute queries can
  build some complex and powerful GIS operations,
  such as weighting.

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Summary

• Database an integrated set of data on a
  particular subject
• Databases offer many advantages over files
• Relational databases dominate

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Part II Working with Attributes in ArcGIS
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Issues to discuss

• how attribute data is stored in a table of rows
  and columns
• how attribute data is associated with features
• tabular field types supported in ArcGIS
• types of table relationships
• how tables can be related to each other
• how to join tables based on a common field

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Review

• A geographic database contains both spatial and
  tabular data. The spatial data contains feature
  shape and location information, while the tabular
  data contains the attributes for the features.
  Often, feature attributes are contained in
  multiple tables.

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Anatomy of a Table

• Each table in a database has the same basic
  format an array of rows and columns. Rows are
  also called records, and columns are also called
  fields.
• Some tables, like a feature class's default
  feature attribute table, have a preset number of
  columns. For instance, a polygon coverage's
  feature attribute table has four standard
  columns Area, Perimeter, Coverage, and
  Coverage-ID, while a line shapefile's feature
  attribute table has only one default column,
  named Shape. Other tables are completely
  user-defined.

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• The table has three user-added columns Name,
  Country, and Population. ArcMap automatically
  adds a third column (FID) for display purposes.
  The name of this column may be different
  depending on the type of data source. For
  example, it is called FID for a coverage or
  shapefile, OBJECTID for a geodatabase feature
  class, and Order_ID for a grid.
• Because some databases and some operations do not
  support fields with blanks in their names, you
  should avoid creating fields that contain them.
  In addition, every column in a table should have
  a unique name but columns in the same table can
  have a variety of formats. NOTE Norwegian æ å
  ø can also create problems, as can decimal
  formats (10,1 versus 10.1).

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Tabular data field types

• Tables are capable of storing date, number, and
  text values, but most tabular formats have
  several different field types to store this
  information.
• Choosing the best field type for the values to be
  stored is an important consideration. Also, the
  available field types can vary between tabular
  formats. In general, you can store numbers, text,
  and dates. Specifically supported formats in
  ArcCatalog include short integer, long integer,
  float, double, text, date, object-id, and blob.

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Information stored in tables is organized by
fields and field types. When defining a table's
fields, be aware that each database has its own
rules defining what names and characters are
permitted.
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ArcGIS Tabular Formats

• ArcGIS supports the use of multiple formats for
  storing and managing tabular data. Each of ArcGIS
  software's primary spatial formats has its own
  native format. Coverages use INFO-formatted
  tables shapefiles store their attributes in
  dBASE (.dbf) format geodatabases rely on the
  format of their supporting RDBMS (Oracle, for
  example).
• Deciding on the proper format in which to store
  attribute information is an important part of
  database design and can affect the efficiency
  with which you are able to access feature
  attributes. To facilitate sharing data that's in
  different formats, ArcCatalog and ArcToolbox
  contain tools to convert between the various
  tabular formats. In addition, some formats, such
  as the coverage, can link to independent tables
  regardless of their format.

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Tabular information can be stored in a variety of
formats. In this case, feature information is
stored in the coverage feature attribute table,
data about the owners is stored in dBASE format,
and tax information is stored in a relational
database format.
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Associating Tables

• Because features often have many attributes, most
  database design guidelines promote organizing
  your database into multiple tableseach focused
  on a specific topicinstead of one large table
  containing all the necessary fields. This scheme
  is more efficient because it eliminates duplicate
  information in the databaseyou store the
  information only once in one table. Tables can be
  "connected" so that when you need information
  that isn't in the current table, you can access
  it from a table associated with it.

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• Two tables can be connected if there is a similar
  field in each table containing common values.
  Each table must have at least one field
  containing unique values for each record in
  database terminology, this field is called the
  primary key. Even if there are duplicate values
  in all the other fields, the primary key ensures
  that each row will be unique.

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• Row uniqueness is important when connecting two
  tables because you want to make sure the correct
  rows are matched together. As a general rule, you
  connect tables from a primary key field in one
  table to the common field (called the foreign
  key) in the other table. In the next graphic, the
  ZONE_CODE field exists in both tables, contains
  common values in each, and has unique values in
  each row in the attribute table on the right. The
  tables can be connected based on this field.

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In each table above, ZONE_CODE contains the same
valuescodes for zoning types. The attribute
table on the right also contains the descriptions
for each code this information is not stored in
the feature attribute table, but it is
information that users will want to access often.
The tables will be connected so that the zoning
descriptions can be easily accessed.
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Table Relationships

• In ArcMap, you can connect two tables using
  either a join or a relate. In order to know which
  method to use, you need to know how individual
  records in each table relate to one another. You
  need to know if one or more than one record in
  the first table is associated with one or more
  than one record in the second table. There are
  four possible relationship types (also called
  cardinality) one-to-one, one-to-many,
  many-to-one, and many-to-many.

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Cardinality

• A property of a relationship between objects in a
  database, describing how many objects of type A
  are associated with how many objects of type B.
  Relationships can have one-to-one, one-to-many,
  many-to-one, and many-to-many cardinalities.
• For example, one parcel can have one owner
  (one-to-one), one parcel can have many owners
  (one-to-many), many parcels can have one owner
  (many-to-one), or many parcels can have many
  different owners (many-to-many).

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Connecting tables with joins

• You can connect two tables together in ArcMap
  using a join. Join works with shapefiles,
  coverages, and geodatabase feature classes. Once
  the tables are connected, you can query,
  symbolize, and analyze your data based on the
  joined values.
• Table joins are designed for one-to-one or
  many-to-one relationships. For other
  cardinalities you should use a relate instead of
  a join. If you join two tables that have
  one-to-many or many-to-many cardinality, you will
  omit all records after the first match for each
  primary key value.

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• When joining two tables, the names of the common
  fields need not be identical but the fields must
  be the same type (e.g., text, date, float, etc.).
  The ArcMap Join Data dialog is where you specify
  which tables you want to join and which fields
  contain the values that will match.
• Joined tables are not permanently connected. The
  fields from one table are appended to the other
  table. You can tell from which table a field
  originates because its source table name displays
  in its field name. You can remove a table join
  whenever you want. Table joins are virtual
  that is, the two tables still exist as separate
  entities.

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Connecting tables with relates

• Another way that you can connect tables in ArcMap
  is by creating a relate. Like joining tables,
  relating tables defines a relationship between
  two tables and is also based upon a common field.
  Unlike joining tables, a relate doesn't append
  the fields of one table to the other. Instead,
  you access data in the related table by selecting
  records in one table and accessing the related
  records in the other table.
• You relate tables instead of joining them when
  there is a one-to-many or many-to-many
  relationship between the tables.

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The Attributes of parcels table and the Owners
table have a one-to-many relationship (a parcel
may have more than one owner). The two tables are
related based on the Parcel_no field. Selecting
vacant parcels in the attribute table selects the
records with matching parcel numbers in the
related table.
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• In ArcMap, you create a relate in the Relate
  dialog by choosing the tables you want to relate
  and the fields in each that the relate will be
  based on. To access data in a related table, open
  one of the tables and select the records for
  which you want to display related records. Click
  Options, point to Related Tables, and click the
  name of the relate you want to access. The
  related table will display with the related
  records selected. It doesnt matter which table
  you open, because in ArcMap table relates are
  bi-directional.

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• If your data is involved in both joins and
  relates, the order in which the joins and relates
  are created is significant. If you have a table
  for which you have created a relate and you join
  another table to it, the relate will be removed.
  If you perform a relate on a joined table, the
  relate is removed when the join is removed. As a
  general rule of thumb, it is best to create your
  joins, then add your relates.

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Join

• Suppose you have a parcels feature attribute
  table and another attribute table that contains
  the names of parcel owners. The graphic below
  shows a one-to-one relationship. Each parcel has
  only one owner, so each record in the feature
  attribute table will relate to one record in the
  owners attribute table. For this type of
  relationship, you would use a table join.

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• The graphics below show both a one-to-many and a
  many-to-one relationship. On the left, one parcel
  can have many owners therefore, the relationship
  is one-to-many. On the right, many parcels can
  have one owner, resulting in a many-to-one
  relationship. For a one-to-many relationship, you
  should create a table relate for a many-to-one
  relationship, you should create a table join.

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• You can also have relationships where many
  features relate to many records in the other
  attribute table. In this situation, many parcels
  could have many owners. This is the most complex
  relationship and can be difficult to manage. For
  this type of relationship, you should associate
  the two tables using a table relate.

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Other items to discuss

• sort, calculate, and freeze data in a table
• create summary statistics
• edit feature attributes using the Attributes
  dialog
• use the Field Calculator to update attribute
  values
• create a graph
• create a report

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• There are a number of ways you can display
  attribute data. You can change the way data is
  displayed in a table, and you can take data out
  of the table and display it as statistics or in a
  graph or report.

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Access and edit attribute data in ArcMap.

• When you want to edit feature attributes, you
  start an editing session. When you're in an
  editing session, you can view the attributes of
  selected features by clicking the Attributes
  button to bring up the Attributes dialog. The
  Attributes dialog has two parts a tree view on
  the left that lists each selected feature, and a
  pane on the right that shows the attribute values
  for the feature currently selected in the tree
  view.

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• If you select features from more than one layer,
  each layer that contains selected features will
  be listed in the tree view. You can access
  individual selected features by expanding their
  layer

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• If you select features from more than one layer,
  each layer that contains selected features will
  be listed in the tree view. You can access
  individual selected features by expanding their
  layer

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• You can edit the attribute values for a single
  feature by clicking next to the field name and
  typing in the new value.

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• If you want to change values for all the selected
  features at once, you can click the layer name
  and type the new value next to the field you want
  to update. In the graphic below, the OWNER values
  for all the selected homes are being changed to
  "Alvi Contracting."

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Table manipulation

• You can manipulate tables to change how data is
  viewed. Right-clicking any field brings up a
  context menu with many choices. You can sort the
  record values in a selected field either in
  ascending or descending order. You can sort both
  numeric and character fields.

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• You can calculate the values of selected records
  using the Field Calculator. In the Field
  Calculator, you can update all the values or a
  selected set of values in a field at one time.

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Using the Field Calculator

• In ArcMap, you can edit feature attributes by
  creating simple calculations or logical
  expressions in the Field Calculator. The Field
  Calculator works on selected features or on all
  features in a layer if there are none selected.
• To access the Field Calculator, first start an
  editing session, then open the desired layer's
  attribute table by right-clicking the layer name
  in the Table of Contents. Choose Open Attribute
  Table and when the table displays, right-click
  the field you want to update. Choose Calculate
  Values to display the Field Calculator.

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• To create an expression in the Field Calculator,
  you combine fields, functions, and operators. As
  you click on fields and functions, they appear in
  the expression box. You can also type directly
  into the box. The expression below will update
  the VALUE field with the results of multiplying
  each feature's area by 1.5.

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Freeze or unfreeze a column

• Freezing a column locks a column as the left-most
  column in the table view. You can then use the
  horizontal scroll bar to see the other columns in
  the table. When you scroll, the frozen column
  remains in place while all other columns move. A
  frozen column is easily identified because it has
  a thick black line separating it from the other
  columns in the table.

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Calculating statistics

• After selecting features on the map or selecting
  records in a table, you may want to calculate
  simple summary statistics for the data. (Cchoose
  the Statistics option from ArcMap's Selection
  menu)
• After you select the layer and field in the
  feature attribute table for which you want
  statistics calculated, a list of summary
  statistics, as well as a frequency distribution
  chart, display in the Selection Statistics
  window.

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Graphs in ArcGIS

• Values for ArcGIS graphs come directly from
  feature attribute tables. You can represent your
  data and analysis results using many styles of
  graphs, including both two- and three-dimensional
  graphs. Some graphs are better than others at
  presenting certain kinds of information. You
  should carefully consider the information you
  want to present before choosing a graph style.

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• Once you've created a graph, you can add it to a
  map in ArcMap's Layout View. When placed on the
  layout, a graph becomes a graphic element that
  you can size and position as desired. Once you've
  placed a graph on a layout, however, it becomes
  static and changes to the graph's source table
  will not be reflected in the graph.

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Reports

• A report presents tabular information about map
  features (from a feature attribute table)
  formatted in an attractive manner. You can choose
  which fields from your table you want to display
  and how you want to display them. Once you've
  created a report, you can place it on your map
  layout with your geographic data or save it as a
  file for distribution.
• A report includes a title, page numbers and the
  current date, summary statistics, images,
  borders, and, of course, the data from the
  feature attribute table.

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• Displaying your data in a report allows you to
  organize your data. You can sort records based on
  the values in one or more fieldsgiven a list of
  cities, you could sort them by total population,
  for example. You can also group records and
  calculate summary statistics. For example, you
  could group cities by their country. It would
  then be easy to see which city has the largest
  population in a given country. You can also
  calculate summary statisticssum, average, count,
  standard deviation, minimum, and maximum values.
• You can export reports to different file types,
  including Adobe's Portable Document Format (PDF),
  Rich Text Format (RTF), or plain text (TXT).