Difference between GIS map and paper or electronic map
What's the difference between a GIS map and a static paper or electronic map?
- A big difference is that GIS maps are dynamic. While you can look at a static map
and see where features are located and even measure approximate distances
between them, you can't do much more than that. With a GIS map, however, you
are in charge.
- You can zoom in and out to see different areas with more or less detail, you can
decide what features you want to see and how they are symbolized, and, most
importantly, you can access a database of information about all the features
shown on the map.
Data frame
In ArcGIS, data frames are the containers for the layers shown on a map. Like here, you
can have multiple data frames in one map document. Basically, a data frame is
equivalent to a map.
Scale
The scale depends on how large your ArcMap window is, large your map display area is,
and how large a box you drew when you zoomed in. The scale is the ratio between the
size of features on the map and the size of those same features on the earth. If the scale
is 1:59,886, that means that one unit on the map is equal to 59,886 units in the real
world—or, that features in the real world are 59,886 times larger than they are on the
map.
Bookmark
A bookmark is like a snapshot—it's an area of the map saved at a particular scale.
Data-view and lay-out view
Note the following visible differences between Data view and Layout view:
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The map layout elements (north arrow, legend, and scale bar) do not display.
In Data view, you see only one map at a time (the active data frame).
In ArcMap, there are two views for working with data: Data view and Layout view.
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In Data view, you explore, edit, analyze, and symbolize data. In Data view, you
can view only one data frame at a time.
In Layout view, you arrange data frames (maps) and add other elements, such as
scale bars, titles, and legends, to create a map layout that can be published in
print or digital form. In Layout view, you can view multiple data frames.
How is a GIS map organized?
As you saw in the exercise, a GIS map consists of one or more data frames. A data frame
contains a collection of thematic layers. Layers, in turn, contain a collection of features
that represent real-world objects.
On a GIS map, features have a location, shape, and a symbol. Features grouped into a
layer have the same shape and characteristics and are located within the same
geographic extent. To make a GIS map, you can add as many layers as you want
Representing the real world
Each feature shape has its own unique set of characteristics.
- A point is composed of one coordinate pair representing a specific location on the
earth's surface.
- A line is a sequence of two or more coordinate pairs.
- A polygon is composed of one or more lines whose starting and ending coordinate
pairs are the same.
o A line has length, while polygons have two intrinsic values, perimeter and
area. Lines represent objects too narrow to be polygons, such as streets,
rivers, and telephone lines.
o Polygons represent objects large enough to have boundaries, such as
countries, building footprints, and lakes.
o Points are used for objects too small to be polygons, such as cities, trees,
and hospitals. The geometry type used to represent an object depends on
the amount of detail that needs to be shown—the same object may be
represented as a polygon in one layer and a point in another layer.
Linking features to information
On a GIS map, there's more to a feature than its location and shape. There's all the
information associated with that feature. A particular type, or category, of information
associated with a feature in a GIS is called an attribute. Feature attributes are stored in
an attribute table. In an attribute table, each feature is a record (row) and each attribute
is a column, or field. The attributes for all the features in a layer are stored in the same
attribute table.
The different programs of ArcGIS Desktop
ArcGIS Desktop is a scalable family of three products, or license levels: ArcView®,
ArcEditor™, and ArcInfo®. All three products look and work the same—they differ only in
how much GIS functionality they provide. ArcEditor provides more than ArcView, and
ArcInfo provides all the functionality of ArcView and ArcEditor plus tools for advanced
spatial analysis, data management, and high-end cartography.
ArcMap is the application you work with to visualize and analyze data and make GIS
maps. ArcCatalog is the application you work with to manage data.
ArcCatalog
- Notice that the datasets are listed alphabetically and that each one has an icon on
its left. The icon indicates the type of feature geometry stored in the dataset—
point, line, or polygon.
- the Tornado database has the .gdb file extension. This indicates that Tornado is a
file geodatabase. A geodatabase is a database that stores GIS data; you will learn
more about geodatabases in Module 4.
Using location to get information
There are four basic types of spatial relationships: distance, containment, intersection,
and adjacency. It's important to understand these spatial relationships because they
provide a basis for making decisions and solving many problems. Getting answers to
questions that are based on spatial relationships is the reason people use a GIS.
Because a GIS stores feature coordinate locations, it can quickly find and select features
that meet some spatial criteria.
Feature spatial relationships (distance,
containment, intersection, and adjacency)
are the basis of solving problems with a
GIS. [Click to enlarge]
The geographic inquiry process: a way to solve problems
Step
Description
1. Ask a geographic
question
Develop geographic questions that need to be answered such
as, "What is the pattern to when and where crime is occurring?"
2. Acquire geographic
data
Obtain the geographic data you need from a company database,
the Internet, other sources, or create it yourself.
3. Explore geographic
data
Create a map of your geographic area and symbolize data.
4. Analyze
geographic
information
Determine problem-solving approach and perform GIS analysis.
5. Act on geographic
knowledge
Develop your message and intended audience and create
visuals, such as maps, to communicate information.
Review
This module introduced you to GIS and ArcGIS Desktop software. A GIS is a computerbased tool for getting information that can be used to make decisions and solve
problems. ArcGIS Desktop is a scalable GIS software product used to interact with maps,
data, and tools. Listed below are key points you should remember.
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A GIS organizes and stores information about the world as a collection of thematic
layers. Each layer contains features with the same shape and attributes, all
located within a common geographic area.
Each feature is assigned a unique numerical identifier and is characterized by a
unique location in space and a corresponding record in a table.
Features can be stored in a GIS as three primary shapes: points, lines, or
polygons.
Features have spatial relationships with other features, and with a GIS you can
find features based on their spatial relationships.
The geographic inquiry process provides a framework for solving problems with
GIS.
Review questions
1. How is a GIS map different from a static map?
2. What is one way you can get information about a feature using ArcGIS Desktop
software?
3. What are the primary operations that a GIS can perform that make it a useful tool
for solving problems?
4. What are the five steps in the geographic inquiry process?
Answer
1. The dynamic nature of a GIS map makes it different from a static map. In a GIS,
map features are linked to a database of information. You can pan, zoom, get
information about features, control feature display, and change how they are
symbolized.
2. You can use the Identify tool to click a map feature and see its attributes. You can
also open the attribute table to view a feature record.
3. A GIS can capture, store, query, analyze, display, and present data.
4. The five steps in the geographic inquiry process are: 1) ask a geographic
question, 2) acquire geographic data, 3) explore geographic data, 4) analyze
geographic information, and 5) act on geographic knowledge.
Module 2
Maps can be divided into two main categories: reference maps (also called general
maps) and thematic maps.
- Reference maps show the location of features and are useful for multiple
purposes—atlas maps and topographic maps are examples of reference maps.
- Thematic maps show the structure and distribution of one or more phenomena.
Examples of thematic maps include maps of world population, today's weather,
and rice production in the Philippines.
Text in maps
In technical terms, text added manually to a map is called annotation. Unlike feature
labels, which come from a field in a layer attribute table, each piece of annotation is
stored either in a map document or in a database.
Annotation and labels behave differently in ArcMap.
- Annotation always stays at the position where you place it, but you can reposition
it as desired.
- The placement of labels, on the other hand, is dynamic and determined by
ArcMap. ArcMap places labels based on the current map extent and the number of
features being displayed. As the map is zoomed in or out and the number of
features increases or decreases, the position of labels will change as ArcMap finds
the best placement for them. Labels may move, appear, or disappear as the
available space on the map changes.
Categories
Category attributes are names, types, or ranks. Each unique attribute value represents a
different category. The values can be text or numbers.
When a layer is symbolized based on a category attribute, features in different categories
are represented with a different symbol. Exactly how the symbols differ from one another
depends on what you are mapping.
Quantities
Quantity attributes are always numeric. The numbers represent counts, amounts, rates,
or measures
Feature quantities are typically represented on a map by creating groups (classes) of
features with similar values and assigning a different symbol to each class. However,
even though the symbols are different, they usually change gradually from one class to
another, forming a series.
Classifying data
- Grouping attribute values into classes
In ArcMap, you can classify features using one of several standard classification methods.
You can also define your own classes. The available classification methods include:
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Natural breaks (Jenks)—identifies groupings of values that are inherent in your
data. This is the default method because it is appropriate for most data.
Equal interval—this method is like a ruler: the interval between each class is the
same. For example, you might have classes with intervals of 10 percent (1-10%,
11-20%, 21-30%, etc.)
Quantile—each class contains an equal number of values (features). For example,
you might have 15 provinces grouped into three classes—each class would contain
five provinces regardless of the attribute values.

Manual—each class has the range you specify. This method is useful when you
want the classes to reflect specific criteria or data. For example, if you have
temperature data, you might want to specify a break between classes at 32
degrees Fahrenheit (freezing point).
-
Deciding which classificantion scheme to use
Classification
method
-
When to use
How many classes to have
Natural breaks
(Jenks)
When attributes are distributed
unevenly across the overall
range of values
Choose a number that best reflects
the natural groups of attributes you
want to show.
Equal interval
When you want all classes to
have the same range
Choose a number that produces an
easily understood interval, such as
2, 50, 1000, etc. Or, choose the
number of classes that produces a
map with your intended message.
Quantile
When attributes are distributed
in a linear fashion (an even
distribution across the range of
values and little variation in the
number of attributes for each
value)
Choose a number that makes sense
for the purpose of your map.
Manual
When you want classes to break
at specific values
Choose the number that makes
sense with your classification
scheme. For example, you would
need two classes to show values
above and below a certain threshold
value.
Explore methods of classifying data
Mapping density and proportion
This topic presents methods for symbolizing maps to show density and proportion
between two attributes.
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Mapping density using attribute values: One way to map density is to divide the
attribute values by the area of each polygon feature. The process of dividing one
attribute by another is called data normalization.
Mapping density visually: Another way to map density is to do so visually by using
dots to represent quantities of things in the real world. This kind of map is called a
dot density map.
o An advantage of the dot density map is that you can estimate the actual
number of people in a census tract (by counting the dots) in addition to
getting a visual sense of density.
o An advantage of the graduated color map is that you can easily pick out an
individual census tract and determine how it compares with those nearby.
Mapping proportion: You can map the relationship between two attributes by
normalizing (dividing) one by the other to produce a ratio. As when mapping
density, normalized data is typically symbolized using graduated colors or
symbols. (Ratios, percentages or rates)
Review:
Feature symbology greatly affects how readers interpret a map. The right symbols can
mean the difference between confusion and clarity—between conveying a little
information or a lot. The right symbols can also reveal patterns in your data that may not
be obvious. Listed below are key points you should remember about symbolizing maps.
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Point, line, and polygon symbols have properties that you can set, such as shape,
size, color, outline, and width.
Effective symbols take advantage of common associations that people make, such
as blue for water or a larger dot for a more populated city.
Symbolizing features by attributes allows you to communicate more information.
You can symbolize features to show categories (names, types, ranks) or quantities
(counts, amounts, rates, measurements).
Quantity attributes can be classified using different methods, including natural
breaks (Jenks), quantile, equal interval, and manual.
Which classification scheme you choose depends on the purpose of the map and
the characteristics of the data—there is no one "correct" choice.
Review questions
1. When you label map features in ArcMap, where does the text come from?
2. When classifying a layer, what rule of thumb can you use to decide how many
classes to use?
3. Name two things you can learn from a classification histogram.
4. Name two ways that density can be symbolized on a map.
Answer
1. In ArcMap, label text comes from a field in the layer attribute table or you can
manually add your own text to a map.
2. When classifying data, fewer classes is generally better.
3. You can learn many things from a classification histogram. Your answer could
have been any of the following:
 How attribute values are distributed across the whole range of values
 The minimum attribute value
 The maximum attribute value
 The number of classes
 The class breaks (maximum value for each class)
 The size of classes relative to one another
 The number of features that have a particular attribute value.
4. You can show density on a map by normalizing an attribute by area and using
graduated color or graduated size symbols; you can also create a dot density
map.
Module 3: Referencing Data to Real Locations
Coordinate systems: the reference systems used to determine feature locations
Understanding coordinate systems
- Geographic (GCS): used to locate objects on the curved surface of the earth.
Graticule: network of intersecting lines (longitude -> meridians and latitude ->
parallels)
Each geographic coordinate system has its own interpretation of the shape of the earth.
Two shapes are commonly used: sphere (small scale maps) and spheroid (large scale
maps)
Datum: specifies which spheroid you are using as your earth model and at which exact
location you are aligning that spheroid to the earth’s surface.
- Projected (PCS): used to locate objects on a flat surface.
Caresian coordinates: right angels intersecting for the longitude and latitude. X and y x
axis. Center (0,0)
False easting: Number added to the x coordinate to make all the numbers in the raster
positive
False northing: Number added to the y coordinate to make all the numbers in the
raster positive.
Working with different coordinate systems
1st layer has GCS, 2nd layer has same GCS but also PCS -> no problem
1st layer has GCS, 2nd layer has different GCS -> problem Arcmap doesn’t guarantee
perfect alignment.
In ArcCatalog it says in Metadata what type of coordinate system the data uses.
Map units: the units in which the coordinates for a dataset are stored. Determined by
the coordinate system
Display units: are independent of map units, they are a property of a data frame.
Working with map projections
A map projection is used to convert data from a geographic coordinate system to a
projected (planar) coordinate system.
- Types of map projections
Cylinder: produce maps with straight, evenly-spaced meridians and straight parallels.
Cone: produce maps with straight converging longitude lines and concentric circular arcs
for latitudes.
Plane: produce maps on which the longitude lines converge at the north pole and radiate
outward. The latitude lines appear as a series of concentric circles
- Understanding distortion
When converting locations from a spherical surface to a flat surface this causes distortion
for 4 spatial properties: shape, area, distance and direction
- Choosing a map projection
Depends on the map’s purpose and the spatial properties you want to preserve.
Characteristics of Map Projections
Projection
Category
Properties
Common Uses
Conformal
Preserves local shapes and angles
Topographic maps,
navigation charts,
weather maps
Equal Area
Preserves areas
Dot density maps,
thematic maps
Equidistant
Preserves distance from one or two
specified points to all other points on
the map
Maps of airline distances,
seismic maps showing
distances from an
earthquake epicenter
Azimuthal
All directions are true from a single
specified point (usually the center) to all
other points on the map
Navigation and route
planning maps
Compromise
No point is completely distortion free;
distortion is minimized near the center
and along the equator
World maps
Review:
The accuracy of a GIS map or analysis depends on the accuracy with which feature
locations are represented. A coordinate system is used to reference feature locations to
the real world. Listed below are key points about coordinate systems that you should
remember.
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All geographic datasets have a geographic coordinate system (GCS).
There are different spheroids for different parts of the world, and there are
different datums to help align the spheroid with the surface of the earth in
different regions.
As long as they have a common geographic coordinate system, ArcMap can
properly display multiple datasets in the same data frame using a process called
"on-the-fly projection."
In ArcMap, the first layer you add to an empty data frame sets the coordinate
system for the data frame.
You should use a map projection when you need to perform analysis, take
accurate measurements, or when you need to show a particular spatial property
as it really exists on the earth.
Anyone who uses maps should know which projections are being used and which
properties are distorted and to what extent.
Review questions
1. What are the components of a geographic coordinate system?
2. Name one way you can get information about the coordinate system of a dataset
in ArcCatalog.
3. What are the two most important factors to consider when choosing a map
projection?
Answer
1. A geographic coordinate system is defined by a prime meridian (usually
Greenwich), a datum (which includes a spheroid), and an angular unit of measure
(degrees).
2. You can use the Description tab to view the coordinate system information for a
dataset. You can also look at the dataset's Properties dialog box.
3. When choosing a map projection, you should consider the purpose of the map and
which spatial properties you want to preserve.
Module 4: Organizing Geographic Data
Exploring geographic data: To represent real-world features digitally, you use a data
model.
- Geographic data models:
Two types: vector and raster data models
o Vector: represents real-world features as points, lines and polygons whose
boundaries are defined by x, y coordinate pairs. Used when features have
discrete boundaries.
o Raster: represents geographic data, like elevation, as rows and columns of
equally sized cells. One corner of the raster must be defined by an x,y
coordinate pair. Can also represent discrete features but more useful for
continuous geographic data.
- Organizing vector data:
Feature class: is a collection of features that share the same geometry type and the
same attributes and that are located within a common geographic extent.
- The geodatabase: big container for all types of features
Feature datasets: stores feature classes that have the same coordinate system.
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Coverage:???
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Shapefiles: type of feature class (collection of features that have the same
geometry typ and common spatial extent) composed out of at least three files,
and as many as eight. In ArcCatalog only the file with the .shp extentsion.
-
Raster data formats: Two common data formats based on the raster data model
are ESRI Grids and imagery.
o ESRI Grids: file format used to store both discrete and continuous data.
Depending on the type of data being sotred cell values can be either
integers (whole numbers, discrete) or floating points (numbers with
decimals, continuous)
o Imagery: collective term for rasters whose cells store brightness values of
reflected visible light or other types of electromagnetic radiation. Can be
displayed as layers in a map or it can be used as attributes for vector
features.
Organizing data into a geodatabase
- Types of geodatabases
o File geodatabases: for small workgroup
o Personal geodatabases : also for small workgroups
o Multiuser ArcSDE geodatabases: for large organizations
-
Designing a geodatabase: ask yourself:
o What will it be used for?
o What data layers do you need?
o Attributes?
o Level of detail? Etc. etc.
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Getting data into a geodatabase:
o Import: when you already have data stored in other formats
o
o
Load: data from multiple source files can be loaded and combined into one
geodatabase feature class
Copy: for geodatabase to geodatabase
Review:
Geographic data is recorded information about the earth's surface and the objects found
on it, associated to a geographic location. Listed below are key points you should
remember about geographic data.
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Two models for representing real-world features in a GIS are the vector data
model and the raster data model.
Geodatabases, shapefiles, and coverages are common file formats for storing
vector data. Imagery and ESRI Grids are common formats for raster data.
There are three types of geodatabases: file geodatabases, personal geodatabases
for Microsoft Access, and multiuser ArcSDE geodatabases that are used with
relational database management systems and ArcSDE technology.
Geodatabase feature classes can be stand-alone or they can be organized into
larger units called feature datasets.
The field type of an attribute determines the type of data that can be stored in it.
Before you build a geodatabase, you need to spend time designing it.
Review questions
1. When would you use the vector data model versus the raster data model?
2. In a geodatabase polygon feature class, which two fields are automatically
calculated and updated?
3. List three methods of adding data to a geodatabase.
4. If you wanted to combine features from different feature classes into one feature
class, which method would you use?
Answer
1. If you want to represent features with distinct boundaries, it is probably better to
use the vector data model and store the feature x,y coordinate locations. The
raster data model is better suited to representing phenomena whose boundaries
change gradually across a given area.
2. For a geodatabase polygon feature class, the Shape_Length and Shape_Area
fields are automatically calculated and updated.
3. Three methods of adding data to a geodatabase are importing, loading, and
copying data.
4. To combine features from different feature classes into one feature class, you
would load them into a new, empty geodatabase feature class.
Module 5: Creating and Editing Data
- Editing feature shapes
Three primary feature geometries: point, line or polygon.
Vertices: x, y coordinate pairs
Segments: connecting the vertices
Multiple steps:
1. Open a map document and add the data you want to edit
2. Start an edit session
3. Choose a feature template
4. Select the feature and display its sketch
5. Make your edits
6. Save your edits
Snapping:
Feature template: define the information required to create a feature: the layer, the
symbology, default attributes a feature should be assigned when created and default
tool
Topology: defines the spatial relationships among features and maintains them during
editing.
o Map topology: identifies and maintains spatial relationships among
features during an edit sessions
o Geodatabase topology: is a set of rules and properties that defines the
spatial relationships you want to model and preserve in your data.
- Editing feature attributes:
Two different ways of editing attributes in ArcMap: attributes dialog box and via the layer
attribute table. Unlike the Attributes dialog box, the attribute table provides a tool that
automates editing. This goes through the Field Calculator.
- Creating new features and attributes
Heads-up digitzing/onscreen digitizing: common way to create new features by
tracing their shapes on screen using another layer for reference.
Base layer: layer used as a reference
2 important aspects:
o Dgitzing scale: don’t zoom in to much or zoom out to far.
o Number of vertices: too many will increase the size of your data, to less
won’t be accurate enough.
Event layer: looks and acts like any other layer in the Table of Contents. However,
features in an event layer are not permantly stored on disk.
Review:
A GIS database is only as good as the information it stores. As features in the real world
change, it is important to edit your data to keep your GIS database current. In ArcGIS,
you can create and edit both feature shapes and attributes. Listed below are key points
you should remember about creating and editing data.
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To edit the shape of a line or polygon feature, you work with its sketch.
You can modify a feature's shape by moving, inserting, and deleting vertices.
Editing the shape of a feature that is spatially related to another feature affects
the other feature's shape—to maintain the integrity of your database, it is
important to maintain feature spatial relationships when editing.
With map topology you can edit spatially related features simultaneously.
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To edit feature attributes, you can manually enter edits in the Attributes dialog
box or in the attribute table.
The Field Calculator automates the process of updating feature attributes.
To create new features, you follow the same process used to edit features.
Review questions
1. What are the steps in the editing process?
2. What is an advantage of using the Field Calculator?
3. Name two ways to create point features.
Answer
1. The steps in the editing process are: 1) add the data you want to edit to a map
document, 2) start an edit session, 3) choose a feature template, 4) select
features to edit and display their sketches (line and polygon features), 5) make
your edits, and 6) save your edits.
2. In the Field Calculator, you can combine text strings, derive values from different
attribute fields, plus use mathematical and logical operators to quickly calculate
attribute values. You can calculate values for all records or only for selected
records.
3. You can create new point features by heads-up digitizing (clicking the point
locations using a base layer for reference) and you can import their x,y coordinate
locations from a text file
Module 6: Getting started with GIS Analysis
- The analytical process
Several steps:
1. Define the problem
2. Define the criteria
3. Identify the data you need
4. Plan the analysis
5. Prepare the data for analysis
6. Execute the analysis
7. Examine and present the results
- Asking questions and getting answers
There are two types of GIS queries: attribute and location
o Attribute: you select features that have one or more attribute values that
meet a particular criterion.
A query expression: logical statement consisting of three parts: a field name
(attribute), an operator and an attribute value.
Result: a selected set of the features in the layer.
Location: you select features whose location meets particular conditions,
usally in relationship to other features.
A query expression: location query is a descriptive statement. With three part: a target
(‘select from’) layer, a type of spatial relationship (distance, containment, intersection
and adjacency), and a spatially related layer.
o
Map:
Examing and presenting the results
o
o
analysis: prepared quickly and visually simple: minimal context only
essential layers and feature labels
Presentation map: includes information that helps explain its context and
purpose. Data layers for orientation, map symbology, label features, add
callout text or graphics.
Reports:
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Choose which attribute fields to include
Include all the records in a table or a selected set
Sort the records based on the values in one or more fields
Group records and calculate summary statistics (such as sum, average, and
count)
Choose what elements to include, such as a title, image, or page number
Choose a tabular format (fields accross the page) or columnar format (fields down
the page)
Review:
A GIS analysis involves visualizing and combining geographic data to derive new
information. GIS analysis does not solve problems directly; the information it produces is
used by people to draw conclusions and make informed decisions. Listed below are key
points you should remember about GIS analysis.
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GIS analysis is an iterative process that includes clearly defining a problem,
identifying criteria and data, planning and executing the analysis, and evaluating
and presenting the results.
An analysis plan can help you identify necessary data and software tools, prevent
mistakes, and save time.
GIS analysis often involves creating queries to select features that meet attribute
or locational criteria.
To access feature attributes stored outside the layer attribute table, you can
create a join between the attribute table and a nonspatial table.
Maps, graphs, tables, and reports can be used to present analysis results.
Review questions
1. What three things should be identified on a workflow diagram?
2. How can you create a report that lists the attributes of only some of the features
in a layer?
3. Why would you create a table join?
Answer
1. A workflow diagram should identify the sequence of steps, the specific tool to use
at each step, and the data required and produced by each tool.
2. To show the attributes of only some features in a report, first create a selected set
of features, then create the report.
3. You would join two tables if you want to query or symbolize a layer based on an
attribute that is stored in a different table than the layer attribute table.
Module 7: Working with Geoprocessing and Modeling Tools
Geoprocessing: integral part of GIS analysis, encompasses any operation that creates
new data from existing GIS data.
Model: a collection of geoprocessing operation that allows you to visualize and automate
an analysis workflow
- Working with geoprocessing tools
Geoprocessing operations can be used for analysis. These tools can be divided into three
categories:
o Data extraction: creating a new subset of features in one feature class
based on the geographic extent of another feature class. Done by Clip.
o
Overlay: combining different layers to create a new layr that contains the
data from both input layers. Union
o
Proximity: involves finding what is near or within a certain distance of one
or more features. Done by Buffer.
Parameters: tool parameters constist of the name an location of the input data set,
values specific to the geoprocessing operation, and the name and location the output
dataset.
In a typical analysis that includes geoprocessing operations, you would follow the steps
below:
1.
2.
3.
4.
5.
6.
7.
Determine which geoprocessing tools you need.
Determine the order in which the geoprocessing tools should be used.
Locate the first tool and open its dialog box.
Enter the tool parameters, including the input and output datasets.
Run the tool.
Repeat steps 3-5 for each geoprocessing tool in order.
Examine the final output and repeat some or all of the analysis steps as needed.
- Creating and using models
ModelBuilder is the graphical environment in which you create and interact with models.
The building block of a model is called a process.
White elements: not ready to run, a tool parameter needs to be entered
Drophadow: the process has run successfully
Why to use models?:
o Models provide a big-picture view of a project
o
o
o
o
o
Models are reusable
Processes run seamlessly faster
Processes can be run individually
Models make managing intermediate data easy
Models can be shared
Review:
Geoprocessing is an integral part of GIS analysis that creates new data from existing GIS
data, from which information can be derived to solve problems. When you need to
perform many geoprocessing operations or want to be able to easily repeat an analysis,
you can create a model to automate and keep track of your workflow. Listed below are
key points you should remember about geoprocessing and models.
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Geoprocessing tools used for analysis typically fall into three categories: data
extraction, overlay, and proximity.
Geoprocessing tools are stored in toolsets, which are stored in toolboxes.
The basic building block of a model is a process; a process consists of a
geoprocessing tool.
In a model, processes are connected to represent and execute a geoprocessing
workflow.
Models can be saved, easily modified, and run as many times as needed to
perform different analyses and test "what if" scenarios.
Like GIS data, models should be documented so they can be shared with others.
Review questions
1. What are some of the steps in a geoprocessing workflow?
2. What do the element symbols in a model indicate?
3. What is one way a model can help you manage data?
Click to see if you were right
Answer
1. In a typical geoprocessing workflow, you need to determine which tools to use
and in what order; find and open the first tool, enter its parameters, and run it;
then repeat for each tool in the sequence. After all the tools have run, you
examine the final output and make adjustments if necessary.
2. Element symbols indicate the state of a process—whether a process is ready to
run or has already run.
3. When you add processes to a model, you can flag their output data as
intermediate data, then delete it after the model runs.
Module 8: Designing Maps with ArcGIS
o present information through a map effectively, you need to ask yourself questions such
as:
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Who is the intended audience?
What is the purpose of the map?
How will the map be used?
- Working with map layouts
Design principles:
o Audience and purpose
o Size, scale, and media
o Visual balance: a map contains more information than just the central
theme, its elements need to be visually ranked according to importance.
Main elements: Map body, legend, title, scale, north arrow, inset map.
- Creating a presentation map
Template: contains a fully designed layout with the standard map elements you need.
How to make it more readable:
- Adjusting layer transparency
- Converting labels to annotation
- Adding a reference system: Graticule, measured grid or a reference grid.
Gebleven bij stap 5 in laatste opdracht