Understanding Map Projections

More documents

Recommendations

Info

POLYCONICDirectionLocal angles are accurate along the central meridian;otherwise, they are distorted.DistanceThe scale along each parallel and along the centralmeridian of the projection is accurate. Distortionincreases along the meridians as the distance fromthe central meridian increases.The central meridian is 90° W.DESCRIPTIONThe name of this projection translates into ‘manycones’. This refers to the projection methodology.This affects the shape of the meridians. Unlike otherconic projections, the meridians are curved ratherthan linear.PROJECTION METHODMore complex than the regular conic projections, butstill a simple construction. This projection is createdby lining up an infinite number of cones along thecentral meridian. This projection yields parallels thatare not concentric. Each line of latitude representsthe base of its tangential cone.LIMITATIONSDistortion is minimized on large-scale maps, such astopographic quadrangles, where meridians andparallels can be drawn in practice as straight-linesegments. Producing a map library with this kind ofmap sheet is not advisable because errorsaccumulate and become visible when joining sheetsin multiple directions.USES AND APPLICATIONSUsed for 7½- and 15-minute topographic USGS quadsheets, from 1886 until approximately 1957. Note:Some new quad sheets after this date have beenfalsely documented as Polyconic. The presentprojection for east–west State Plane CoordinateSystem zones is Lambert Conformal Conic, andTransverse Mercator for north–south state zones.LINES OF CONTACTMany lines; all parallels of latitude in the projection.LINEAR GRATICULESCentral meridian of the projection and the equator.PROPERTIESShapeNo local shape distortion along the central meridian.Distortion increases with distance from the centralmeridian; thus, east–west distortion is greater thannorth–south distortion.AreaDistortion in area increases with distance from thecentral meridian.78 • Understanding Map Projections
QUARTIC A UTHALICUSES AND APPLICATIONSThematic world maps. The McBryde–Thomas Flat-Polar Quartic projection is based on this projection.The central meridian is 0°.DESCRIPTIONThis pseudocylindrical equal-area projection isprimarily used for thematic maps of the world.PROJECTION METHODPseudocylindrical equal-area projection.LINEAR GRATICULESThe central meridian is a straight line 0.45 times thelength of the equator. Meridians are equally spacedcurves. Parallels are unequally spaced, straightparallel lines perpendicular to the central meridian.Their spacing decreases very gradually as they moveaway from the equator.PROPERTIESShapeGenerally distorted.AreaEqual area.DirectionDirection is generally distorted.DistanceScale is true along the equator. Scale is also constantalong any given latitude and is symmetrical aroundthe equator.LIMITATIONSUseful only as a world map.Supported map projections• 79
Page 1 and 2:
Understanding Map ProjectionsMelita
Page 3 and 4:
ContentsCHAPTER 1: GEOGRAPHIC COORD
Page 5:
State Plane Coordinate System .....
Page 8 and 9:
GEOGRAPHIC COORDINATE SYSTEMSA geog
Page 10 and 11:
SPHEROIDS AND SPHERESThe shape and
Page 12 and 13:
DATUMSWhile a spheroid approximates
Page 15 and 16:
2ProjectedcoordinatesystemsProjecte
Page 17 and 18:
WHAT IS A MAP PROJECTION?Whether yo
Page 19 and 20:
PROJECTION TYPESBecause maps are fl
Page 21 and 22:
maintained for both small-scale and
Page 23 and 24:
Planar projectionsPlanar projection
Page 25 and 26:
OTHER PROJECTIONSThe projections di
Page 27:
The four parameters above are used
Page 30 and 31:
GEOGRAPHIC TRANSFORMATION METHODSMo
Page 32 and 33:
Unless explicitly stated, it’s im
Page 34 and 35: National Transformation version 2Li
Page 36 and 37: LIST OF SUPPORTED MAP PROJECTIONSAi
Page 38 and 39: LoximuthalMcBryde-Thomas Flat-Polar
Page 40 and 41: AITOFFUSES AND APPLICATIONSDevelope
Page 42 and 43: ALASKA SERIES ELIMITATIONSThis proj
Page 44 and 45: AZIMUTHAL EQUIDISTANTAreaDistortion
Page 46 and 47: BIPOLAR OBLIQUE CONFORMAL CONICDESC
Page 48 and 49: CASSINI-SOLDNERAreaNo distortion al
Page 50 and 51: CRASTER PARABOLICDistanceScale is t
Page 52 and 53: DOUBLE STEREOGRAPHICOblique aspect
Page 54 and 55: ECKERT IIThe central meridian is 10
Page 56 and 57: ECKERT IVparallels. Nearer the pole
Page 58 and 59: ECKERT VIcentral meridian. Scale is
Page 60 and 61: EQUIDISTANT CYLINDRICALLINES OF CON
Page 62 and 63: GALL’S STEREOGRAPHICAreaArea is t
Page 64 and 65: GEOCENTRIC COORDINATE SYSTEMGeograp
Page 66 and 67: GNOMONICPROPERTIESShapeIncreasingly
Page 68 and 69: HAMMER-AITOFFLIMITATIONSUseful only
Page 70 and 71: KROVAKDirectionLocal angles are acc
Page 72 and 73: LAMBERT CONFORMAL CONICAreaMinimal
Page 74 and 75: LOXIMUTHALDistanceScale is true alo
Page 76 and 77: MERCATORGreenland is only one-eight
Page 78 and 79: MOLLWEIDEDistanceScale is true alon
Page 80 and 81: ORTHOGRAPHICPROPERTIESShapeMinimal
Page 82 and 83: PLATE CARRÉEDirectionNorth, south,
Page 86 and 87: RECTIFIED SKEWED ORTHOMORPHICDESCRI
Page 88 and 89: SIMPLE CONICEquirectangular project
Page 90 and 91: SPACE OBLIQUE MERCATORDESCRIPTIONTh
Page 92 and 93: Montana—The three zones for Monta
Page 94 and 95: TIMESLIMITATIONSUseful only for wor
Page 96 and 97: 10,000,000 meters to ensure that al
Page 98 and 99: UNIVERSAL POLAR STEREOGRAPHICAreaTh
Page 100 and 101: VAN DER GRINTEN IDistanceScale alon
Page 102 and 103: WINKEL IDistanceGenerally, scale is
Page 104 and 105: WINKEL T RIPELDistanceGenerally, sc
Page 107 and 108: Glossaryangular unitsThe unit of me
Page 109 and 110: High Accuracy Reference NetworkA re
Page 111: UTMSee Universal Transverse Mercato
Page 114 and 115: Eckert VI 52ED 1950 6Ellipse 101Ell
Page 116: Projections (continued)planar 17, 1
show all

Understanding Map Projections

Create successful ePaper yourself

Delete template?

Save as template?