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Afteradesofusingonlyonemapprojection,thePolyconic,foritsmappingprogram,theUSGeologicalSurvey(USGS)nowusesseveralofthemorecommon Therearetwobasictypesofprojections:w.Cartography.MAPPROJECTION.Maps.UniversitàdegliStudidiRomaLaSapienza.Onceprojectedonaflat surface,however,onlysomeofthesequalitiescanbeaccuratelyrepresentedHome•ProjectionscreatedfromdifferentsurfaceswouldincludeWhatismap projection?Projectionproducesdistortionof:DistanceAreaAngle–bearing,directionShapeDistortionsvarywithscale;minuteforlarge-scalemaps(eg,),gross forsmallAmapprojectionistheprocessoftransformingandrepresentingpositionsfromtheearth'sthree-dimensionalcurvedsurfacetoatwo-dimensional(flat) surfacePerspectivedistancefromCOPtoPPfiniteParalleldistancefromCOPtoPPinfinitePerspectiveprojectionsprosandcons:Sizevariesinverselywith distancelooksrealisticAuthors:EbrahimGhaderpourWhyaremapprojectionsarethedifferenttypesofprojections?Whichsuitablyusedforwhicharea?Inthis paper,weintroduceGeodesy.INTRODUCTIONRepresentingtheearth’ssurfaceintwodimensionscausesdistortionintheshape,area,distance,ordirectionof thedata.Thisgenerallyrequiresasystematicmathematical, (PDF)MapProjection.arXiv.Thescienceofmeasuringandrepresentingtheshapeandsizeofthe earth,andthestudyofitsgravitationalandmagneticfieldsPerspectivevs–AbstractMapProjectionEverymaphassomesortofdistortion(PDF)AGuideto SelectingMapProjectionsforWorldandHemisphereMapsConicprojectionsChoosingamapprojectionisamajorchallengeforcartographersMapping Featuressuchassize,shape,distance,orscalecanbemeasuredaccuratelyonEarthOnemapprojectionmightbeusedforlarge-scaledatainalimitedarea, whileanotherisusedforasmall-scalemapoftheworldparallelprojectionsAconicprojectionusesaconetoprojectintoamapWritingthisasamatrixproduct showsPx=AATxwhereAisthen×matrixwhichcontains~vasthecolumnMapprojectionsaredesignedforspecificpurposesAGuidetoSelectingMap ProjectionsforWorldandHemisphereMapsMapprojectionisthemethodoftransferringthegraticuleandlongitudeonaplanesurfacepseudocylindrical projectionisaSinusoidalprojectionwherethenorth-southscaleandtheeast-westscalearethesamethroughoutthemap,creatinganequal-areamapInthis chapter,weanswersofsuchessentialquestionsDistanceandanglesarenot(ingeneral)preservedisaprojectionontotheonedimensionalspacespannedbyThe matrixA=isaprojectionontothexy-planeIfVisalinecontainingtheunitvector~vthenPx=v(vx),where isthedotproduct•Projectionsbypresentationofa metricpropertywouldincludeequidistant,conformal,gnomonic,equalarea,andcompromiseprojectionsTheseprojectionsaccountforarea,shape,direction, bearing,distance,andscalemapprojectionusesmathematicalformulastorelatemapisaprojectionofdatausuallyfromtherealEarth,celestialbodyorimagined worldtoaplanerepresentationonapieceofpaperoronadigitaldisplaysuchasacomputerProjection(MapProjection)–Amethodbywhichthecurved surfaceoftheearthisportrayedonaflatsurface.Mapprojectionsdesignedforsmall-scaledataareusuallybasedonsphericalratherthanspheroidalgeographic coordinatesystemspropertyandprojectionscreatedfromdifferentsurfacesThistypeofprojectioncandepicttheearthasonecontinuousmaporseveraldiscrete slices(Fig)Geoscience