# Introduction to Cartography GEOG 2016 E - PowerPoint PPT Presentation

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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

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## 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

GIS VectorFormat

GIS RasterFormat

Map Feature

### Vector and Raster Representations

GIS VectorFormat

GIS RasterFormat

Map Feature

### 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