Understanding Map Projections

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ALASKA SERIES ELIMITATIONSThis projection is appropriate for mapping Alaska,the Aleutian Islands, and the Bering Sea region only.USES AND APPLICATIONS1972 USGS revision of a 1954 Alaska map that waspublished at 1:2,500,000 scale.1974 map of the Aleutian Islands and the Bering Sea.Parameters are set by the software.DESCRIPTIONThis projection was developed in 1972 by the USGSto publish a map of Alaska at 1:2,500,000 scale.PROJECTION METHODApproximates Equidistant Conic, although it iscommonly referred to as a Modified TransverseMercator.LINES OF CONTACTThe standard parallels at 53°30' N and 66°05'24" N.LINEAR GRATICULESThe meridians are straight lines radiating from acenter point. The parallels closely approximateconcentric circular arcs.PROPERTIESShapeNeither conformal nor equal area.AreaNeither conformal nor equal area.DirectionDistortion increases with distance from the standardparallels.DistanceAccurate along the standard parallels.36 • Understanding Map Projections
ALBERS EQUAL A REA CONICparallels are preserved, but because the scale alongthe lines of longitude does not match the scale alongthe lines of latitude, the final projection is notconformal.AreaAll areas are proportional to the same areas on theearth.DirectionLocally true along the standard parallels.The central meridian is 96° W. The first and second standardparallels are 20° N and 60° N, while the latitude of origin is40° N.DESCRIPTIONThis conic projection uses two standard parallels toreduce some of the distortion of a projection withone standard parallel. Although neither shape norlinear scale is truly correct, the distortion of theseproperties is minimized in the region between thestandard parallels. This projection is best suited forland masses extending in an east-to-west orientationrather than those lying north to south.PROJECTION METHODConic. The meridians are equally spaced straightlines converging to a common point. Poles arerepresented as arcs rather than as single points.Parallels are unequally spaced concentric circleswhose spacing decreases toward the poles.LINES OF CONTACTTwo lines, the standard parallels, defined by degreeslatitude.LINEAR GRATICULESAll meridians.PROPERTIESShapeShape along the standard parallels is accurate andminimally distorted in the region between thestandard parallels and those regions just beyond.The 90 degree angles between meridians andDistanceDistances are most accurate in the middle latitudes.Along parallels, scale is reduced between thestandard parallels and increased beyond them. Alongmeridians, scale follows an opposite pattern.LIMITATIONSBest results for regions predominantly east–west inorientation and located in the middle latitudes. Totalrange in latitude from north to south should notexceed 30–35 degrees. No limitations on theeast–west range.USES AND APPLICATIONSUsed for small regions or countries but not forcontinents.Used for the conterminous United States, normallyusing 29°30' and 45°30' as the two standard parallels.For this projection, the maximum scale distortion forthe 48 states is 1.25 percent.One method to calculate the standard parallels is bydetermining the range in latitude in degrees north tosouth and dividing this range by six. The ‘One-SixthRule’ places the first standard parallel at one-sixththe range above the southern boundary and thesecond standard parallel minus one-sixth the rangebelow the northern limit. There are other possibleapproaches.Supported map projections• 37
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 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 84 and 85: POLYCONICDirectionLocal angles are
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
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Understanding Map Projections

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