Introduction to Cartography GEOG 2016 E

1. Introduction to CartographyGEOG 2016 E Lecture-6 Data Processing and Classification

2. 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.

3. Classification • Classification means grouping values into classes such that the required geographic patterns become prominent.

4. 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

5. 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

6. Class Boundaries – Natural Break • Natural Break • Class boundaries are choses when there is appreciable change in data. • Classes may have different widths.

7. Class Boundaries – Standard Deviation • Standard Deviation • Class boundaries are chosen with respect to deviation from the mean. • Classes may have different widths. σ 

8. Simplification • Simplification means changing geometry such that relevant details get pronounced and irrelevant details get suppressed. Line Simplification Area Simplification

9. 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

10. 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

11. 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

12. 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 • ……

13. Geographic Representation • In geography each variable can be represented in different ways: • Polygons • Grids • TIN (Triangular Irregular Network) • Sample points • Contours

14. Spatial Data Grid co-ordinate Placename Latitude / Longitude Postcode Description Distance & bearing

15. 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

16. 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

17. 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

18. 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

19. GIS VectorFormat GIS RasterFormat Map Feature Vector and Raster Representations

20. GIS VectorFormat GIS RasterFormat Map Feature Vector and Raster Representations

21. 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.

22. 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.

23. 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.

24. 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.

25. 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