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Introduction to Cartography GEOG 2016 E. Lecture-6 Data Processing and Classification. Cartographic Data Management. Management of data to produce a map consists of following steps: Selection Preliminary steps to gather the appropriate data. Classification Simplification

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introduction to cartography geog 2016 e

Introduction to CartographyGEOG 2016 E

Lecture-6

Data Processing and Classification

cartographic data management
Cartographic Data Management
  • Management of data to produce a map consists of following steps:
    • Selection
      • Preliminary steps to gather the appropriate data.
    • Classification
    • Simplification
      • These are the data processing steps.
classification
Classification
  • Classification means grouping values into classes such that the required geographic patterns become prominent.
class boundaries equal interval
Class Boundaries – Equal Interval
  • Equal Interval
    • The whole range is divided into equal intervals called classes.
    • Each class is filled with the number of values found in the corresponding interval.

l1

l2

l3

l4

l5

class boundaries quantile
Class Boundaries - Quantile
  • Quantile
    • Each class is creates such that it contains equal number of values.
    • The classes may have different widths.

a1

a2

a5

a4

a5

class boundaries natural break
Class Boundaries – Natural Break
  • Natural Break
    • Class boundaries are choses when there is appreciable change in data.
    • Classes may have different widths.
class boundaries standard deviation
Class Boundaries – Standard Deviation
  • Standard Deviation
    • Class boundaries are chosen with respect to deviation from the mean.
    • Classes may have different widths.

σ

simplification
Simplification
  • Simplification means changing geometry such that relevant details get pronounced and irrelevant details get suppressed.

Line Simplification

Area Simplification

storing information
Storing Information
  • To generate maps we need data.
  • These data can be in analog or digital form.
  • The generated map can also be in analog or digital form.
  • Analog
    • World is scaled to a miniature representation
    • A paper map is analog
  • Digital
    • Data and map are stored in computer memory
    • Manipulation and analysis of data and maps are possible
geographic information
Geographic Information
  • A piece of geographic information can have location, time and attribute
  • Analog information
    • It’s cold today in Sudbury
  • Digital information
    • At 46.45783 degrees latitude and -81.00443 degrees longitude at 7 am the temperature was -10 degrees Celsius
discrete objects
Discrete Objects
  • Objects on a map are represented by points, lines and areas
  • These discrete objects can be stored in a digital database
  • They can then be:
    • Analyzed
    • Manipulated
    • Counted
parameters
Parameters
  • There are a number of parameters that are important in terms of geographic representation.
    • Temperature
    • Soil pH
    • Soil type
    • Land type
    • Elevation
    • Rainfall
    • Taxation rate
    • Population
    • ……
geographic representation
Geographic Representation
  • In geography each variable can be represented in different ways:
    • Polygons
    • Grids
    • TIN (Triangular Irregular Network)
    • Sample points
    • Contours
spatial data
Spatial Data

Grid co-ordinate

Placename

Latitude / Longitude

Postcode

Description

Distance & bearing

characteristics of spatial data
Characteristics of Spatial Data

Geometry

  • The shape of a building or county
  • The course of a river, the route of a road
  • The shape of the landscape, relief
characteristics of spatial data1
Characteristics of Spatial Data
  • Topology
      • Connected to
      • Within
      • Adjacent to
      • North of . . .
  • Example
      • Within the town of Lively
      • Opposite the Fraser building
      • South of main library
      • Adjacent to the Parker building
data modeling steps
Data Modeling Steps
  • Identify the important features
  • Decide how you can best represent them: point, line, polygon
  • Find the important attributes related to all the features
  • Store information in a geographic database
digital data formats

GIS VectorFormat

GIS RasterFormat

Map Feature

(X,Y)Coordinate in space

Cell Locatedin an Array

Digital Data Formats
  • In geography, there are two main digital data formats:
    • Raster
    • Vector
comparison raster and vector formats
Comparison: Raster and Vector Formats

Raster

Vector

  • Raster formats are efficient when comparing information among arrays with the same cell size.
  • Raster files are generally very large because each cell occupies a separate line of data, only one attribute can be assigned to each cell, and cell sizes are relatively small.
  • Vector formats are efficient when comparing information whose geographical shapes and sizes are different.
  • Vector files are much smaller because a relatively small number of vectors can precisely describe large areas and many attributes can be ascribed to these areas.
digital databases
Digital Databases
  • There is no single database that can store every imaginable piece of geographic information.
  • Specialized databases have been developed to handle selected pieces of spatial data.
  • Some of these databases are in proprietary formats while others are in open formats.
thematic database
Thematic Database
  • A thematic database contains special datasets associated with a particular activity.
  • Soil Survey Geographic Database or SSURGO contains the attributes related to soil. This database has been developed by the Soil Conservation Service of the US Department of Agriculture.
  • Similarly, the National Wetland Inventory or NWI has constructed a database that contains information on wetland location and types.
digital elevation database
Digital Elevation Database
  • Digital Elevation Model or DEM consists of an array of regularly spaced elevations.
  • The United States Geological Survey or USGS provides a number of DEM databases with different array spacings and geographical coverages.
  • In Canada, GeoBase provides DEM in support from Natural Resources Canada.
digital image data
Digital Image Data
  • More and more governmental and private agencies are starting to provide digital imagery.
  • These photos are based on satellite and aerial photography
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