What is a map? A simple representation of the real world Two types of maps

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1 Mapping with GIS

2 What is a map? A simple representation of the real world Two types of maps Reference maps showing reference features such as roads, locations, political boundaries, cities etc. Thematic maps maps on special themes maps on a particular theme or a special topic.

3 Types of Maps Reference maps general information about the location of features Ex; Road maps Thematic or statistical maps show the distribution of a specific topic Ex; Population distribution maps Food Accessibility Natura Miles N Kilometers N Food Affordability and Accessibility Classification Type - Natural Break Roads Critically Vulnerable Area Vulnerable Area Moderately Vulnerable Area Less Vulnerable Area Least Vulnerable Area North and Eastern provinces Sri lanka

4 Type of Thematic Maps Choropleth maps Map showing quantitative data as a colour Can show the quantity, average value, density, percentage of an event within a geographical area Sequential colour increasing or decreasing vales

5 Type of Thematic Maps Proportional or graduated symbols represent data associated with point locations such as cities Data is displayed on these maps with proportionally sized symbols to show differences in occurrences

6 Types of thematic maps Isarithmic (Isopleth) or contour maps uses isolines to depict continuous values like precipitation levels Isarithmic maps also follow the basic rule that there is a high and low side in relation to the isoline data for isarithmic maps is gathered via measureable points (e.g. - weather stations) or is collected by area (e.g. - tons of corn per acre by county).

7 Types of thematic maps Dot density maps Uses dots to show the presence of a theme and display a spatial pattern On these maps, a dot can represent one unit or several, depending on what is being depicted with the map

8 Types of thematic maps Dasymetric maps is a complex variation of the choropleth map works by using statistics and extra information to combine areas with similar values

9 General Mapping Concepts All maps are representations. Model of the earth at a reduced scale 3D objects 2D display. map projection are use to transfer from 3D to 2D Symbols represent Actual objects Symbols should be easily understood by the map reader

10 Composition of a map Map Title Legend Scale Other information that required for complete presentation data 30 Food Accessibility Natural Br Food Accessibility 0 30 Miles N Food Affordability and Accessibility Classification Type - Natural Breaks Critically Vulnerable Area Vulnerable Area Moderately Vulnerable Area Less Vulnerable Area Least Vulnerable Area North and Eastern provinces

11 Map Scale Maps - models of the earth indicates the relationship between a certain distance on the map and the distance on the ground A ratio or representative fraction (RF) indicates how many units on the earth's surface is equal to one unit on the map It can be expressed as 1/100,000 or 1:100,000 word statement gives a written description of map distance; Eg. "One centimeter equals one kilometer graphic scale Suitable when the maps are modified using photocopying etc. Large and small scales scsle should be sufficient enough to display required information

12 Symbolization Assigning symbols to represent features Map symbolization is the characters, letters, or similar graphic representations used on a map to indicate an object or characteristic in the real world Factors considered selecting symbols for a map Map Scale Nature of the phenomenon being mapped Available data

13 Mapping Understanding the data Geographic Dimension Type of geographic features Points features Ex; Airports, oil wells Line Features Ex; Railways, highways Areal features Ex; Districts, forest areas In some cases feature type decides by the map scale

14 Mapping Measurement Level of data Qualitative data Quantitative data Data can be Nominal - basically refers to categorically discrete data such as name of your school, type of car you drive or name of a book. Ordinal - refers to quantities that have a natural ordering, With ordinal data you cannot state with certainty whether the intervals between each value are equal. Interval - data is like ordinal except we can say the intervals between each value are equally split, Eg. temperature in degrees Fahrenheit. The difference between 29 and 30 degrees is the same magnitude as the difference between 78 and 79. Ratio - interval data with a natural zero point, time is ratio since 0 time is meaningful. Degrees Kelvin has a 0 point (absolute 0) and the steps in both these scales have the same degree of magnitude.

15 Mapping Choosing symbols Visual Variables Size Shape Orientation Pattern Hue value

16 Mapping combinations of data and symbols Location data Points low values small symbols high values large symbols Dotted values Density high High value For Quantitative data shaded area map low values - light high values - dark When colour use different shades of a single hue light red medium red dark red

17 Quantitative and Qualitative data

18 Classification Necessary to classify the data before mapping maximize the between-class differences minimize the within-class differences Several approaches to classify data Understanding basic statistics is important Mean Standard deviation Data distribution

19 Classification Equal range Equal distance between class breaks Useful enumeration areas are of equal size

20 Classification Quantiles Equal number of observations in each class Class intervals can be dramatically different in size

21 Classification Standard deviation Class breaks based on distance of standard deviation from the mean Useful - Data that is normally distributed

22 Classification Natural breaks Class breaks conform to gaps in data distribution mathematically minimizes variation within classes and maximizes variation between classes.

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26 What is Map Projection? Apply a Model. Sphere,Ellipsoid or Geoid Scale the model. (Usually Reduction) Apply Transformation

27 Map Projections Set of rules for transforming features from the threedimensional earth onto a two-dimensional display. All map projections distort the surface in some way Map projections differ in the way they handle four properties: Area Angles Distance Direction

28 Map Projections Equal Area projections preserve areas Conformal projections Equidistant projections -preserve distance from some standard point or line Azimuthal projections - directions from a central point are preserved Compromise projections - seeking a balance between distortions or make things "look right

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30 Projections by surface Three developable surfaces (plane, cylinder, cone) provide useful models for understanding, describing, and developing map projections

31 Transverse Mercator Projection

32 Transverse Mercator Projection

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34 Conical Projection

35 Azimuthal Projection

36 Universal Transverse Mercator Projection (UTM) Cylindrical projection system Presented by Gerardus Mercator in 1569 preserving the angles and the shapes of small objects conformal The system instead divides the Earth into sixty zones, each a six-degree band of longitude.

37 Datum Transformation Kandawala WGS84 Everest WGS84 Reference Ellipsoid Used by GPS

38 Coordinate Sri Lanka National Grid Piduruthalagala #

39 T. M. Parameters Latitude N Longitude E Scale False Northing m False Easting m