Geographic Information Systems Overview

Geographic Information Systems (GIS)

Passing or Failing

  • Factors determining success:
    • Attending classes.
    • Punctuality.
    • Paying attention.
    • Submitting assignments on time.
    • Working smart.
    • Consulting with instructors.
    • Asking questions and participating in class.
    • Making a deliberate choice to pass.

Quote for the Semester

  • "The capacity to learn is a GIFT; the ability to learn is a SKILL; the willingness to learn is a CHOICE." - Brian Herbert

Introduction to GIS

  • Many professionals are becoming interested in learning GIS to better understand their environment.
  • Environment refers to the geographic space of a study area and the events that occur there.
  • Examples of professions using GIS:
    • Urban planners: studying urban fringe growth and quantifying population growth in suburbs.
    • Biologists: assessing the impact of slash-and-burn practices on amphibian species.
    • Natural hazard analysts: natural hazard risk profiling.
    • Geologic engineers: determining optimal building locations in earthquake-prone areas by analyzing rock formations.
    • Mining engineers: identifying best prospect copper mines based on extent, depth, and ore quality.
    • Geoinformatics engineers: finding best sites for telecommunication relay stations considering land prices and terrain.
    • Programmers: developing algorithms for spatial analysis and studying human behavior using big data (e.g., Twitter, Facebook, WhatsApp).
  • All these professionals work with data related to space and positional information.
  • Positional data indicates where things are, were, or will be.
  • The primary purpose of GIS is to maintain data about geographic space.
  • The world is constantly changing, necessitating monitoring of these changes, both natural and man-made.
  • Most GIS applications focus on understanding phenomena with geographic, temporal, and spatial-temporal dimensions, considering variations based on location and time.
  • GIS can be defined by the stages of working with geographic data:
    • Data preparation and entry.
    • Data analysis: reviewing data to discover patterns.
    • Data presentation: presenting analysis results appropriately.

Definition of GIS

  • A computerized system that facilitates data entry, analysis, and presentation, especially when dealing with georeferenced data.
  • Functionality includes:
    • Support for various coordinate systems.
    • Methods for computing with georeferenced data.
    • Flexibility in presentation parameters like color scheme, symbol set, and medium.
  • Other definitions:
    • A computer system capable of assembling, storing, manipulating, and displaying geographically referenced information.
    • An organized collection of computer hardware, software, geographic data, and personnel for efficient data management.

GIS Description: Primary Roles

  • Collection: Gathering data from various sources like remote sensing, terrestrial surveys, and paper maps.
  • Storage and management: Administering and tracking data, including integrating various datasets into a common database for efficient digital storage.
  • Retrieval: Easy and efficient selection and viewing of data in a variety of ways.
  • Conversion: Changing data from one form or map format to another, or converting geographic projections to make data more useful.
  • Analysis: Analyzing data to produce insight and new information using data investigation techniques, statistical procedures, and other methodologies.
  • Modelling: Simplifying data to understand how things work, explaining data meaning, generalizing data, or providing a simple explanation of reality (e.g., creating a contour map from elevation data).
  • Display: Presenting data in various formats like maps, graphs, and reports for easy understanding.

GIS Features

  • Users expect to define requirements and interact with the system through a user-friendly interface (icons).
  • An information system aims to improve decision-making ability.
  • It involves a chain of operations from planning data collection to data storage, analysis, and the use of derived information in decision-making.
  • Maps are examples of GIS outputs.

GIS Components

  • Six primary components of a GIS:
    • Organization and people
    • Applications
    • Methodology
    • Data
    • Software
    • Hardware

GIS Components Explained

  • Organization and people:
    • The most important part of a GIS infrastructure.
    • GIS needs dedicated people and facilities for success.
  • Applications:
    • Uses, questions, or “customers” of GIS.
    • The purpose of its production, such as environmental analysis or city planning.
  • Methodology:
    • Procedures, techniques, and ways of using GIS data.
    • The problem being addressed determines the approach.
    • It also determines the type of data to be used.
  • Data:
    • The heart of GIS operations.
    • Much emphasis is on the data, from input through analysis to presentation.
    • The nature of the data determines the methodology.
  • Software:
    • Computer programs needed to run GIS (e.g., ArcGIS, QGIS).
  • Hardware:
    • The machinery on which GIS operates, including computers, printers, plotters, and digitizers.

GIS as Multidisciplinary

  • Uses data and techniques from many professions and academic disciplines, with applications in diverse fields.
  • Adopted by phone companies, banks, advertising firms, emergency services, and many public and private activities.
  • A major information and decision-support technology.
  • Ideal for dealing with multidisciplinary problems because it integrates data from various sources with different formats.

Are Maps True Representations of Reality?

  • Maps can be distorted.
  • Example: Countries that fit into Africa.

Map Distortions

  • Canada, Russia, the United States, and Europe appear greatly enlarged on some maps.
  • Distortion is largest near the poles.
  • Greenland appears about the same size as Africa on the Mercator projection, but in reality, it is no bigger than the Democratic Republic of Congo.

Geographic Data and Databases

  • GIS uses spatial data as its primary component.
  • Spatial data occupies geographic space and has a specific location according to a world referencing system.
  • GIS datasets contain spatial data and associated nonspatial data, all termed spatial data.
  • Geographic data consists of location, shape, and size as spatial components.
  • Descriptions and associated data are the nonspatial attributes.

Geographically Referenced Data

  • This differentiates GIS from other information systems.
  • Data describes both the locations and characteristics of spatial features.
  • These are termed spatial data and attribute data, respectively.
  • Spatial data is further categorized into two types: discrete features and continuous features.

Discrete and Continuous Phenomenon

  • Two basic measures of the geographic landscape:
    • Discrete data:
      • Distinct features with definite boundaries and identities.
      • Constitute separate entities.
    • Continuous data:
      • Does not have definite borders or distinctive values.
      • Transition from one measure to another is implied.

Examples of Discrete and Continuous Features

  • Discrete features:
    • Individually distinguishable features that do not exist between observations.
    • Examples include points (wells), lines (roads), and areas (land use types).
  • Continuous features:
    • Features that exist spatially between observations.
    • Examples include elevation, temperature, and precipitation.
    • These features are represented on a map within the GIS environment.

Attribute Data

  • Describes the characteristics of spatial features.
  • For a land parcel, the attribute data could include:
    • Name of owner
    • Size of land parcel
    • Contacts of owner

Types of Spatial Data

  • Three main types of spatial data:
    • Point:
      • A spot (or location) that has no physical or actual spatial dimensions but does have a specific location.
    • Line:
      • One-dimensional feature having only length, no width.
      • Has a beginning and an end.
      • Represents linear features that are either real (roads or streams) or artificial (administrative and property boundaries).
    • Polygon:
      • An enclosed area.
      • A 2D feature with at least three sides.
      • Examples: agricultural fields, land parcels, and political districts.

Data Models

  • Vector (Points, Lines, Polygons)
  • Raster (Cell, Pixels, Elements)

Vector Data Model

  • Points, lines, and polygons.
  • More closely resembles the real world.

Advantages of Vector Data Model

  • Less data redundancy.
  • Discrete features are represented clearly and continuously.
  • Topology of spatial features can be more clearly identified.
  • Greater precision in computation of spatial properties and processing of map features.

Disadvantages of Vector Data Model

  • Complex data structure.
  • Expensive technology.
  • Analysis is complex.

Raster Data Model

  • Areas broken into pixels or cells.
  • Each cell contains data.
  • Good at representing dense data, such as land cover and elevation.

Advantages of Raster Data Model

  • Simple data structure.
  • Cheap technology.
  • Simple analysis.
  • Same grid cell for several attributes.

Disadvantages of Raster Data Model

  • Large data volume.
  • Inefficient use of computer storage.
  • Difficult network analysis.
  • Less accurate or attractive maps.
  • Loss of information when using large cells.

GIS and the 4 Ms

  • Like any other Information System, GIS is associated with 4 Ms based on the key activities involved:
    • Measurement
    • Monitoring
    • Modelling
    • Mapping

Terminologies

  • Data: \text{Representations that can be operated upon by a computer}.
  • Spatial data: Data that contains positional values.
  • Information: \text{Data that has been interpreted by a human being}. Human perception and mental processing leads to information, and hopefully understanding and knowledge.

Applications of GIS

  • Applications exist for both man-made structures and the natural environment (e.g., boundaries of natural vegetation and land parcels).
  • A second distinction in applications of GIS stems from the overall purposes of use of the system.
  • Project-based GIS applications versus institutional GIS applications.
  • \text{Priori defined where as the other has no priori defined or is indefinite}

Spatial Data Relationships

  • Features on maps relate to one another in different ways.
  • Tobler’s first law of geography.
  • Some of the relationships are listed below:
    • Distance:
      • \text{Shortest path connecting two points}.
      • Can easily be deduced using a scale.
    • Distribution: Collective location of features; dispersal of features.
    • Density: \text{Number of items per unit area}.
    • Pattern: Consistent arrangement of features.

Proximity Relationships

  • Three common proximity / neighborhood characteristics:
    • Connectivity:
      • Considers features that connect or at least touch.
      • Connected features may have some meaningful association.
      • Streams that connect may be part of the same hydrologic system.
      • Stream and road connection could indicate a bridge or drainage pipe.
    • Contiguity:
      • This is another aspect of connectivity.
      • Polygons with shared borders probably have functional relationships proportional to the amount of border that is shared.
    • Adjacency:
      • Nearness or the features that are close to each other.
      • Buffer zones are usually used.

Time and GIS Data

  • Time is an important data quality element.
  • Can be expressed in terms of data quality, dynamic data and trends.
  • Very important in understanding the processes affecting and shaping physical and cultural landscapes.
  • Dynamic data: \text{Changing data}.
  • The universe is continually evolving.
  • Time is an important attribute to consider.
  • Trends:
    • Determined by comparison of data over time (temporal trends).
    • Spatial trends: \text{changing shape, size or position over time}.
    • Non-spatial: \text{changing attributes}.

The GIS Database