Maps and Mapping - Malareo

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Maps and Mapping - Malareo

Understanding MapsWhat is a map?Lots of definitions• Most Simple• “Maps show us where places and things are located and help us find ourway from one place to another.”We Read Maps – Hence Map reading• Need to understand the language– a title - stating what the map shows (e.g. land use or vegetationcover)– a key/reference /legend - so the reader knows what the symbolson the map represent (Map Alphabet)– compass points - showing which way is up (North)– a scale - so the reader can translate distances shown on the mapinto distances on the ground


Understanding MapsTypesGeneral Reference Maps• (Basic maps showing features(Atlases)• Country/ocean/road/riverPlanimetric Maps (Plans ofobjects)• (Maps that represents only thehorizontal positions of features i.e.has no altitudes)• Cadastral maps: showing theboundaries of properties, includesownership, property name, land-usetype or zoning.Cadastral Concept (FIG, 1995)


Topographic Maps (ShowLandform and Elevation),• (Large scale map using contours orcolours to represent relief (shapeand altitude)• Topographical map (showingtopography and landforms)Topocadastral (1:50 000)• (includes Cadastral data such asproperty boundaries, roads,buildings)


Thematic Maps (Shows themes)• (Maps showing information about 1 or more topics)• Soil• Geology• Population• Temperature• RainfallCharts (Marine/Aeronautical)• Used for traveling by sea or air


Map Elements


Map ElementsTitle (What is the map showing)Symbols representing reality(Places, Roads, Areas, Quantities)Examplesof mapelementsFrame(Boundary of map)Mapped AreaLegend /Reference(What thesymbols mean)Source: ESRI virtual CampusDescriptive text(Where the data is from,Who made the map,the date etc)Distance indicator(Scale bar rep. Fraction)Direction indicator(North Arrow,Graticule)


What makes a MapSymbols(The map alphabet) – Reference/Legend/KeyDirection(N/S/E/W 0 – 360) – Compass and BearingLocation(Lat Lon) - Degrees minutes SecondsScale(1:50 000) – Verbal, Bar, FractionHeight(Contours 100m msl) – indicating altitude


Map Symbols► Communicate Geographical Information effectivelyA Map is a simplification of an environment.Abstraction is used to simplify features.= OnnieAbstracted Symbols used to represent features


Cartographic AbstractionProcess of transforming collected data into a graphicalrepresentation of features on a map.Makes maps more legible by removing noise or redundantdata.Uses 4 possible processesSelectionGeneralizationClassificationSymbolization


SelectionProcess of choosing/selecting geographic features touse on the mapRoadsRiversPrimary SchoolsSecondary SchoolsClinicsMunicipal Boundaries


GeneralisationProcess of simplifying geographic features on a mapEliminates unnecessary detailMaintains the visual clarity or legibility of the map.• Grouping many points into one (Huts into a settlement)• Decreasing the complexity of lines (Smoothing roads to remove kinks)• Amalgamate many polygons into one (Magisterial districts into a province)


ClassificationThe process of arranging into classes or categories tosimplify and clarify presentation► Used mainly with thematic maps toassign values to classes• 4 different scales of measurementused► Nominal (no inherent order =Qualitative)► Ordinal (uses categories of rank forcomparison)► Interval (uses exact intervals e.g.temperature)► Ratio (uses exact intervals with anabsolute zero)012345678910A (0 – 4)B (5 – 6)C (7 – 9)D (10)


ClassificationDifferent methods ofThematicClassificationavailable:• Need to use theoptimal method basedon data and desiredoutput• Statistically based


SymbolisationThe process of choosing the symbols you will use torepresent features or quantitiesHouseClinicSmall HouseMedium HouseLarge HouseVSRiverSwampSmall HouseMedium HouseLarge House


Reference or LegendDefines the Symbols used onthe mapSelf explanatory symbols canbe omittedCities, Roads, Rivers iflabelled need not be included.


ScaleIndicates the amount of reduction on a map or allowsthe user to measure distances.1:50,000 scale map.At this scale, 1 cm on the map represents 50,000 cm onthe ground (= 500 metres or 0.5 kilometres).3 typesRepresentative fraction• (1:50000)Verbal Scale• (1 cm equals 5 km)Scale Bar


OrientationRefers to the indication of directionon a mapUsually done using a North Arrow(and/or magnetic north)North is usually at the top of thepage, but include indicator unless it isobviousIf North is not a constant direction(i.e. Map covers a Large area)graticules should be used(Meridians of longitude)


Compass DirectionCardinal PointsNorth – Naughty / NeverEast – Elephants / EatSouth – Squirt /West – Water /SilkWormsSE• Intercardinal Points• NE, NW, SE, SW• SSW, NNE etc.


BearingUses 0 – 360 0 of a circle/compassClockwise from 0Bearing is taken from one point to another using N asthe 0 reference clockwise to the second point


Magnetic DeclinationTrue North – The North Pole• Lines of longitude meetMagnetic North – The Earths MagneticField• Use Magnetic Compass to get direction• Large Lump of Molten Iron in the Earth’s Core• Moves around (1987 – 1990 moved 24‘westwards for PMB)• Different dependant on where you are on the globe• Can calculate the change over time– Original + (Years x Change)– 2011 – 1990 =21 years x Change


Location/PositionLongitude and LatitudeMeasure position Using Meridians and ParallelsLongitude and Latitude


Longitude and LatitudeUse direction N/S/E/W from:• Greenwich Meridian 0• (E+/W-)• Equator 0• (N+/S-)Uses angle to measure distance• Degrees 90 0• Minutes 60’• Seconds 60”RSA is S (–ve) and E (+ve)Therefore -29 0 S +30 0 E


Longitude / Latitude0 – 90 0 Latitude N and S0 – 180 0 Longitude E and W60” in 1’60’ in 1 0Use Downright ruleFormatOr29 0 36’ 45” S 31 0 24’ 12” E-29 0 36’ 45” 31 0 24’ 12”• Can use Decimal degrees -29.5807466 31.4508653


Longitude / LatitudeShown on 1: 50 000 as a grid on the sides of themap sheet1 ‘ intervals with 5’ numbersUse these grids to get positions of places offmaps


ReferencesFIG, 1995. Statement on the Cadastre. Report prepared for the International Federation ofSurveyors by Commission 7 (Cadastre and Land Management). http://www.fig7.org.uk/ Accessed15 August, 2000.http://www.spaceage.co.in/cadastral-surveys.php

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