Geography 3056: Introduction to GIS

1
Working with Spatial Data

• Geography 3056 Introduction to GIS
• Department of Geography Geology
• Nipissing University
• Autumn 2008

2
Review Introduction to GIS

• Introduction
• Development of GIS
• GIS Software
• Data Models
• GIS Operations

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Spatial Data

• Georeferenced Data
• Properties
• i) Location
• ii) Attributes
• iii) Topology

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Spatial Data

• Importance of Location
• i) Data Integration
• ii) Analysis

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Spatial Data

• Components
• i) Datum
• ii) Projections
• iii) Co-ordinate Systems
• (NB. terminology in ArcGIS)

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Sources

• Most common sources
• i) Maps
• ii) Remote Sensing
• iii) Digital Spatial Data
• (e.g. Global Positioning Systems)

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Sources

• Considerations
• i) Primary vs. Secondary data
• ii) Compatibility w/ objectives
• iii) Common Georeferencing System
• iv) Common Scale

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Datum

• Defn
• Datum is a mathematical model of the Earth used
  to project and/or calculate geographical
  co-ordinates.
• Most Datum are based on a spheriod
• i) NAD 27 is based on the Clarke (1866)
  spheriod
• ii) NAD83 is based on the GRS80 spheroid
• iii) WGS84 is also based on GRS80 spheroid

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Datum

• Datum are particularly important for horizontal
  accuracy, i.e. horizontal shifts
• e.g. 10-100 m in the x and y see fig 2.5.

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Projections

• Defn A projection is a systematic
  transformation of the datum onto a plane.
• Distortion of Properties
• (i.e. area, distance, direction)
• Categories of Projections
• i) Equivalent
• ii) Conformal
• (NB. mutually exclusive)

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Co-ordinate Systems

• Defn A co-ordinate system used to reference the
  location of spatial features.
• Categories of Co-ordinate System
• i) Relative Systems
• (e.g. Geocoding)

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Co-ordinate Systems

• ii) Absolute Systems
• a) Geographical Co-ordinates
• i) Angular Measures
• (see fig 2.2)

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Co-ordinate Systems

• ii) Absolute Systems
• a) Geographical Co-ordinates
• ii) Positive and Negative Values
• iii) Format
• (e.g. DMS and DD)

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Co-ordinate Systems

• ii) Absolute Systems
• b) Plane Co-ordinates
• i) Cartesian Co-ordinates
• ii) Types
• (e.g. UTM)

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Co-ordinate Systems

• UTM Co-ordinate System
• i) Purpose
• ii) Divides world into 60 zones
• (see fig. 2.12)

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Co-ordinate Systems

• UTM Co-ordinate System
• iii) Each zone is mapped in a secant transverse
  Mercator projection (see fig. 2.13)

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Co-ordinate Systems

• UTM Co-ordinate System
• iv) Accuracy (1 in 2500)

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Georeferencing in ArcGIS

• Two Types
• i) Geographic
• ii) Projected
• Georeferencing
• i) Predefined
• ii) Imported from Existing Data
• iii) Customised

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Georeferencing in ArcGIS

• Methods
• i) Project on the fly
• a) Defaults to first data layer displayed
• b) The co-ordinate system of the actual data
  layer is not changed

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Georeferencing in ArcGIS

• Methods
• ii) Define Projection Tool
• a) Defines/labels the projection
• b) The co-ordinate system of the actual data
  layer is not changed

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Georeferencing in ArcGIS

• Methods
• iii) Project Tool
• a) Projects/re-projects the data layer into a
  different co-ordinate system

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Scale

• Defn
• Does digital spatial data have a scale?
• Importance
• i) Accuracy
• ii) Resolution

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Scale

• Appropriate Scale
• i) Source data
• ii) Application
• Common scale
• i) Mapping
• ii) Analysis