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Geographic Context
 

Geographic Context

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September 2012 GIS ToT Webinar

September 2012 GIS ToT Webinar

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    Geographic Context Geographic Context Presentation Transcript

    • Geographic Context
    • Everything happens somewhere
    • Knowing where things happen canhelp us understand why thingshappen.
    • Location and Health There is a close link between geography and health.
    • Question What are some ways that people‟s health can be affected by geography?Geography can affect health through landscape, location of services, location of population in need, human interaction with landscape
    • Medical geography A branch of geography that looks at the relation between location and people‟s health Concepts are useful beyond medical geography Long history of use of geography to understand health and disease patterns.
    • John Snow cholera map 1854 London Used map to illustrate cholera outbreak was centered around a pump on Broad St Locking pump led to decrease in disease
    • Malaria in India
    • Maps Valuable tool for displaying data and helping people understand data and direct action Picture of a place which can give you a better understanding When well-made, a map can give both content and context
    • Important Properties of Maps When creating maps there are four factors that are important  Scale  Legend  Title  SourceAll affect the context of data displayed and how the data is and can be INTERPRETED
    • Scale of a Map What is scale? It is the „representative fraction‟ and states therelationship between the distance on the map (such as one centimeter) and the distance on the ground (such as one kilometer) Why is scale so IMPORTANT? The scale affects the level of detail a map shows
    • Map ScaleLarge-scale maps cover small areas, but caninclude a higher level of detail than small-scalemaps which depict larger areas at lower detail.There are no precise definitions of large- or small-scale, but formost map users, the following general scale categories apply:• Large-scale: 1:250 to 1:1,000• Medium-scale: 1:1,000 to 1:10,000• Small-scale: 1:10,000 to 1:100,000• Very Small-scale: 1: 100,000 to above Source: ICIMOD, 2000
    • Large Scale Small Scale1:50,000 1:500,000
    • Scale What are the general rules with scale?  Do not zoom below the scale as stated for the dataset (that is scale at which the data was collected)  Only integrate GIS datasets that have been collected at the same or at a similar scale  The maximum scale a dataset should be viewed is approximately 100 times the Scale that is stated in the Metadata.  For Example: Data collected at 1:5,000 should not be viewed above 1:500,000
    • NorthTitle Arrow Scale Bar Legend Data Source
    • TYPES OF MAP
    • Concentration of Vulnerable Population-Meerut City POPULATION DISTRIBUTION (Using 2 Km Radius)Graduated Circle MapSize of symbol corresponds to data.Advantages:•Easily see extreme ends of thedata distribution•Geographic patterns emergeDisadvantages•Can be challenging to differentiatethe middle of the distribution sincethe eye can‟t easily detect smalldifferences in size Map credit UHRC
    • ChoroplethPolygons are shaded to match datadistributionAdvantages:•Easy to see geographic distribution•Easy for most people to interpretDisadvantages•Polygons can hide unevendistributions within boundaries•If patterns/colors aren‟t chosenwisely the map can be difficult tointerpret
    • 2002 2004 2002 2004Continuous surfacemapsData is distributed continuouslyacross spaceAdvantages:• Very easy to see hot spots or areas that deviate from other areasDisadvantages• Not all data can be distributed continuously Depiction of Malaria incidences in Trans Yamuna Region (Allahabad D Low High High Low Village-wise Slide Positivity Rate (Malaria) of Trans-Yamuna Region 2002 2004
    • Other typesWith advanced software it‟spossible to produce diagram mapsthat display data using charts.Advantages•Effectively displays complexinformation•Lots of information on each mapDisadvantages•Can have too much information•Can be difficult to structure data toproduce such maps•Requires an advanced GIS
    • Which map style should you use? Depends on type of data you have What purpose you want the map to serve Sometimes a matter of experimentation to find the map style that best fits the data and purpose of the mapIt‟s important to pick the type of map that makes the data most useful
    • Basic cartographic concepts Map Design  Cartographic standards  Generalization  Graphic Variables  Use of Color  Classification of Data  Methods of Mapping
    • Map DesignMap making is both science and art.Maps influence people‟s perception of space. Thisinfluence is partly because of convention and partlybecause of the graphics used.People understand the world differently, express thisunderstanding differently in maps, and gain differentunderstanding from the maps.
    • Cartographic standardsThere are cartographic standards that have emerged thatmake it easier to interpret and read maps.These standards do not have to be followed, but if they aren‟tyour map may be less readable.
    • AdministrativeBoundaries--Most often black orgray.--The higher theadministrative unitthe thicker the line
    • RoadsColor and line styles torepresent road type withmajor roads beingthicker or moredistinctively colored thanminor roads.
    • Rivers and Lakes--Blue--Streams dashed,lines light blue
    • Map DesignGeneralization  Maps contain a certain level of detail depending upon the scale and purpose.  Sometimes the map maker will need to simplify features to make them more readable.
    • Use of ColorColor perception has psychological, physiological andconventional aspects.It has been noted that it is difficult to perceive color in small areas,and more contrast is perceived between some colors thanbetween others.In addition to distinguishing nominal categories, color differencesare also used to show deviations or gradation. Hue Saturation Intensity Source: ICIMOD
    • Use of Color Color blindness  5-8% of men  0.5% of women
    • Black-and-white Consider method of reproduction or output of maps
    • Making an effective map is amatter of finding the right balancebetween the limitations of thedata, the needs of the map readerand the message you, as the mapmaker, want to convey.
    • Issues to RememberMaps can LIE!! Maps are just one person‟s representation of the “real world” Like any source of information they can be misleading especially when used out of context How maps can be deceiving  Inappropriate Legend  Inappropriate Scale  Inappropriate Data Classification Source: ICIMOD,
    • Key points Everything happens somewhere Geography is a common denominator across human activity There are different types of maps. Picking the right style means balancing the needs of the reader, the data and the message you as mapmaker want to convey.
    • Key points The mapmaker can use colors, symbology, and generalization techniques to make maps readable to the audience.
    • Any questions?