Geographic Information System Basics
Geographic Information System Basics (v. 1.0)
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Table of Contents
About the Authors
Acknowledgments
Dedications
Preface
Chapter 1: Introduction
Spatial Thinking
Geographic Concepts
Geographic Information Systems for Today and Beyond
Chapter 2: Map Anatomy
Maps and Map Types
Map Scale, Coordinate Systems, and Map Projections
Map Abstraction
Chapter 3: Data, Information, and Where to Find Them
Data and Information
Data about Data
Finding Data
Chapter 4: Data Models for GIS
Raster Data Models
Vector Data Models
Satellite Imagery and Aerial Photography
Chapter 5: Geospatial Data Management
Geographic Data Acquisition
Geospatial Database Management
File Formats
Data Quality
Chapter 6: Data Characteristics and Visualization
Descriptions and Summaries
Searches and Queries
Data Classification
Chapter 7: Geospatial Analysis I: Vector Operations
Single Layer Analysis
Multiple Layer Analysis
Chapter 8: Geospatial Analysis II: Raster Data
Basic Geoprocessing with Rasters
Scale of Analysis
Surface Analysis: Spatial Interpolation
Surface Analysis: Terrain Mapping
Chapter 9: Cartographic Principles
Color
Symbology
Cartographic Design
Chapter 10: GIS Project Management
Project Management Basics
GIS Project Management Tools and Techniques
About the Authors
Jonathan E. Campbell: Adjunct professor at UCLA and Santa Monica College, GIS analyst and biologist at ENVIRON, with 12 years of experience in GIS, environmental policies, and geospatial data analysis. Degrees from UCLA, Southern Illinois University—Carbondale, and Taylor University.
Michael Shin: Associate professor of geography at UCLA, director of UCLA’s professional certificate program in GIST, and cochair of the Spatial Demography Group at CCPR. PhD from CU Boulder. Teaches GIS, digital cartography, spatial analysis, and geographic data visualization. Nominated for UCLA’s Copenhaver Award. Works with the Food and Agricultural Organization of the United Nations and USAID.
Acknowledgments
Thanks to Michael Boezi, Melissa Yu, Jenn Yee, and Scott Mealy.
Colleagues: Rick Bunch, Mark Leipnik, Olga Medvedkov, Jason Duke, I-Shian (Ivan) Shian, Peter Kyem, Darren Ruddell, Victor Gutzler, Wing Cheung, Christina Hupy, Shuhab Khan, Jeffrey S. Ueland, Darcy Boellstorff
Michela Zonta, Ke Liao, Fahui Wang, Robbyn Abbitt, Jamison Conley, Shanon Donnelly, Patrick Kennelly, Michael Konvicka, Michael Leite, Victor Mesev, Scott Nowicki, Fei Yuan, Michela Zonta
Dedications
Campbell: To Walt, Mary, and Reggie Miller.
Shin: To my family.
Preface
Maps are now colorful, searchable, interactive, and shared, reflecting the integration of technology and geographic data. GIS is the key technology.
GIS integrates data and information as maps, giving new meaning to the question of “where.”
Essentials of Geographic Information Systems integrates key concepts with practical concerns and real-world applications.
The book is accessible, pragmatic, and concise, illustrating how GIS is used to ask questions, inform choices, and guide policy.
Learning involves knowing how and where to search for information, as GIS and related technology change rapidly.
Readers are encouraged to construct their own individual frameworks of GIS knowledge through active learning and research.
The book outlines valuable cartographic guidelines and effective GIS project management solutions.
Chapter 1: Introduction
Stuff Happens… somewhere. Knowing where helps us understand what, when, how, and why.
A geographic information system (GIS) answers “where” to understand the world.
GIS is used to organize, analyze, visualize, and share data at various scales and historical periods.
Applications range from climatology to epidemiology, archaeology, and political consulting.
GIS is about geography and learning about the world.
Recognizing and increasing geographical awareness improves the use and application of GIS.
Spatial Thinking
Mental maps are maps of our environment stored in our brains, used for navigation and understanding.
Mental maps reflect geographic knowledge and spatial awareness.
Mental mapping exercise illustrates what you know, how you relate to your environment, and how humans think spatially.
Comparing mental maps reveals similarities and differences in spatial thinking.
Reveals artistic and cartographic abilities.
Filling gaps in mental maps requires asking questions about the world. Questions unlock answers, knowledge, and understanding.
Five general types of geographic questions:
Location: Where is it? Why is it here?
Distribution: Is it local or global? Clustered or dispersed?
Association: What else is near it? What occurs with it?
Interaction: Is it linked to something else? What is the nature of the association?
Change: Has it always been here? How has it changed?
GIS assists in answering these questions, opening up additional avenues of inquiry.
Geographic Concepts
Key concepts: location, direction, distance, space, and navigation.
These concepts establish a framework for learning and applying a GIS and communicating geographic information.
Location: The concept that distinguishes geography
a position on the surface of the earth. Defined in nominal or absolute terms.
Nominal locations: Defined by name (e.g., city names). Toponymy studies place names.
Absolute locations: Use a reference system (e.g., latitude and longitude). Geocoding assigns coordinates.
Postal codes and street addresses follow local logic.
GNIS database for naming standards
GPS technology: Uses 24 satellites to triangulate location.
The network of satellites orbiting the earth, transmitting signals from which latitude and longitude can be obtained with GPS units.
Relative location: Defines places in relation to other known locations
Direction: Position relative to something else.
Egocentric direction: Uses ourselves as a benchmark.
Landmark direction: Uses a known landmark as a benchmark.
True north: Based on the Earth’s rotational axis.
Magnetic north: Point on Earth where magnetic fields converge.
Grid north: Direction of latitude and longitude grid lines.
Distance: Measured in nominal or absolute terms.
Space: Abstract concept, described rather than measured.
Topological space: Concerned with relationships and connectivity.
Transportation maps illustrate topological spaces.
Navigation: Destination-oriented travel through space.
Involves motor skills, technology, mental maps, and awareness.
Geographical knowledge is continuously updated.
Landmark knowledge: Locating and identifying points of interest.
Route knowledge: Connecting and traveling between landmarks.
Survey knowledge: Understanding landmark relationships and taking shortcuts.
Acquired in stages, influencing sense of direction.
Geographic Information Systems for Today and Beyond
GIS is software, hardware, a service, a tool, a system, and a science.
Software perspective: Computer program for storing, editing, processing, and presenting geographic data as maps.
Hardware: Computer, memory, storage devices, scanners, printers, GPS units.
Tool: Maintains, analyzes, and shares data. Used across sectors.
People unify GIS through learning, application, development, and study.
Three Approaches to GISs:
Application approach: GIS is primarily a tool to answer questions, support decision making, and maintain data.
Developer approach: Concerned with improving and extending the GIS as a software or technology platform.
Science approach: (GIScience) Concerned with broader questions, including geography, cognition, map interpretation, accuracy, errors, and social implications of GIS technology. (e.g Privacy and locational privacy)
GIS Futures: The geospatial web integrates Internet content with geographic information via geotagging.
Chapter 2: Map Anatomy
Maps are essential components of GIS and are both input and output.
Cartography: the formal study of maps and mapping.
This chapter defines maps, describes map types, explains map scale, coordinate systems, map projections, and discusses map abstraction.
Maps and Map Types
Maps are artistic, scientific, preserve history, clarify, reveal the invisible, and inform the future.
Map makers have power and influence. Types of Maps: the reference map, thematic map, dynamic map.
Maps are a representation of the world (stored in our brain, printed on paper, or appearing online) to describe various aspects of the world.
Reference Maps:
Deliver location information.
Geographic features and map elements treated equally.
Represent geographic reality accurately (e.g., topographic maps, image maps).
Critical to local and national governments, and navigation devices.
Thematic Maps:
Concerned with a particular theme or topic.
About how things are distributed across space.
Often abstract concepts made visible.
Reference and thematic maps are not mutually exclusive. They complement each other.
Dynamic Maps:
Changeable or interactive representations of the earth.
Refer more to how maps are used and delivered.
They can be reference or thematic maps.
Encourage and require user interaction (e.g., zooming, selecting features, starting/stopping animation).
Map Scale, Coordinate Systems, and Map Projections
Expectations of map viewers are formed from previous experience and change with exposure to maps.
Mapping conventions are accepted rules, norms, and practices behind the making of maps (e.g."north is up").
Most important cartographic considerations: map scale, coordinate systems, and map projections.
Map Scale:
Reduces the world to a manageable size. It is represented by text, a graphic, or both.
Scale bar: Allows users to approximate distances.
Representative fraction (RF): Scale as a ratio (e.g., 1:10,000). One unit on the map represents 10,000 units on the ground.
Can be “small” or “large.” RF of 1:1,000 is large-scale compared to 1:1,000,000.
More detail and less area in large-scale maps.
Less detail and more area in small-scale maps.GISs are multiscalar.
Coordinate Systems:
Frameworks that define unique positions.
Geographic coordinate system (GCS) is based on a sphere or spheroid, using latitude and longitude in degrees.
Latitude: Measured relative to the equator.
Longitude: Measured relative to the prime meridian.
Can be expressed in degrees-minutes-seconds (DMS) or decimal degrees (DD).
Datum: Specifies the orientation and origins of latitude and longitude.
Local datums (e.g., NAD83) are accurate locally. Global datums (e.g., WGS84) are more consistent globally.
Map Projections:
Methods to transform the spherical Earth to two-dimensional surfaces.
Mathematical formulas translate latitude and longitude to x and y coordinates.
Three surfaces used: plane, cylinder, and cone.
Introduce distortions in distance, angles, and areas.
Equidistant projections: Accurately represent distances.
Conformal projections: Represent angles (bearings).
Equal area/equivalent projections: Preserve area.
Choice depends on the purpose of the map. Overlay analysis requires all map layers to be in the same projection.
Map Abstraction
Also, you should have the information that Map abstraction is the process of explicitly defining and representing real-world features on a map.
Geometric form of geographic features.
Point, line, and polygon (or area).
Clear and consistent definitions are critical
Map generalization is simplification in order to be represented on a map.
Chapter 3: Data, Information, and Where to Find Them
Maps are shared, available, and distributed unlike at any other time in history.
Mapping has also been decentralized and democratized and digital map production and consumption.
Digital maps are highly changeable, exchangeable, and dynamic in terms of scale, form, and content.
To understand digital maps and mapping, it is necessary to put them into the context of computing and information technology.
Then, this chapter provides an introduction to the building blocks of digital maps and geographic information systems (GISs), with particular emphasis placed upon how data and information are stored as files on a computer.
Data and Information
Data: Facts, measurements, characteristics, or traits of an object of interest.
Information: Knowledge of value obtained through the collection, interpretation, and/or analysis of data.
Geographic data: Geographic facts, measurement, or characteristics of an object that permits us to define its location on the surface of the earth.
Attribute data: Are concerned with its nongeographic traits and characteristics.
The data and information is the stuff of computer files (of Files and Formats).
File: Container of a complex set of instructions. They come in all different sizes and types. One of the clues we can use to distinguish one file from another is the file extension.
Extension: filename.txt (Simple text file ), filename.doc (Microsoft Word document), filename.pdf (Adobe portable document format ), filename.jpg (Compressed image file), filename.tif (Tagged image format), filename.html, filename.xml, filename.zip
What you will realize as you begin to work more with information technology, and GISs in particular, is that familiarity with different file types is important.
Rows are for records; columns are for fields.
A database is a collection of multiple files