Introduction to Cartography GEOG 2016 E

1 / 25

# Introduction to Cartography GEOG 2016 E - PowerPoint PPT Presentation

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

I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.

## PowerPoint Slideshow about ' Introduction to Cartography GEOG 2016 E' - ami

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.

- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript

### Introduction to CartographyGEOG 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
• These are the data processing steps.
Classification
• Classification means grouping values into classes such that the required geographic patterns become prominent.
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
• 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
• Natural Break
• Class boundaries are choses when there is appreciable change in data.
• Classes may have different widths.
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 means changing geometry such that relevant details get pronounced and irrelevant details get suppressed.

Line Simplification

Area Simplification

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
• A piece of geographic information can have location, time and attribute
• 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
• 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
• 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
• In geography each variable can be represented in different ways:
• Polygons
• Grids
• TIN (Triangular Irregular Network)
• Sample points
• Contours
Spatial Data

Grid co-ordinate

Placename

Latitude / Longitude

Postcode

Description

Distance & bearing

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 Data
• Topology
• Connected to
• Within
• North of . . .
• Example
• Within the town of Lively
• Opposite the Fraser building
• South of main library
• Adjacent to the Parker building
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

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

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
• 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
• 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 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
• More and more governmental and private agencies are starting to provide digital imagery.
• These photos are based on satellite and aerial photography