map projection 1

8/17/2019 Map Projection 1

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Size and Shape of the Earth

Geoid

Datum

Reference Ellipsoid


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“A m ap is a graphic representation of themilieu” (1976, Robinson and Petchenik)

Maps can either be tangible (or “real”) or

v i r tua l in nature Men ta l m ap s are also developed in our minds

over time by the accumulation of manysensory inputs


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The art, science and technology of makingmaps, together with their study as scientificdocuments and works of art. In this contextmay be regarded as including all types ofmaps, plans, charts and sections, three-dimensional models and globes representingthe Earth or any celestial body at any scale(1973, International CartographicAssociation)


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Geographic cartography is distinct from other branches of cartography because it is both a tooland a product of the geographer

The geographic cartographer understands thespatial perspective of the physical environment

and has the skills to abstract and symbolize thisenvironment

The cartographer specializing in this branch ofcartography is skillful in map projectionselection and the mapping and understanding of

areal relationships, and has a thoroughknowledge of the importance of scale to the finalpresentation of spatial data (1954, Robinson)


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Furthermore, geographic cartography,involving an intimacy with the abstraction ofgeographical reality and its symbolization tothe final map product, is capable of“unraveling” or revising the process, that is,geographic cartographers are very adept atmap reading (1981, Muehrcke)


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Descar tes , a Frenchmathematician of the 17th century devised a systemfor the geometricinterpretation of algebraic

relationships, which led tothe development ofanaly t ic geom etry

One of his remarkablecontributions is the concept

of Car tes ian coordina tege ome t r y


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When describing real-world space in theCartesian system, it is common amongcartographers and land surveyors to use theterms eas t ings and nor th ings

A number of cartographic systems are setupso that the origin is always to the south andwest of the coordinate spaces

False origin, false easting and false northing


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The Earth’s geometry is more complex because of its spherical shape

To specify a location on Earth (or anyspherical body), angular measurements must

be used in addition to the elements of theordinary plane system

Sex age s im al s cale : division of a circle into

360 degrees, each degree into 60 minutes andeach minute to 60 seconds◦ DMS (degrees, minutes, seconds)


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Lati tude is simply the location on the Earth’ssurface between the equator and either theNorth or South Pole◦ It is a function of the angle between the horizon

and the North Star (or some other fixed star)

◦ As one travels closer to the pole, the angleincreases

◦ Designated in angular degrees, from 0° at the

equator to 90° at the poles◦ Labels N or S to indicate whether the position is

north or south of the equator, respectively


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Longitude, as compared to latitude, is muchmore difficult to determine◦ Because the Earth rotates on its axis, there is no

fixed point at which to begin counting position◦

The Earth rotated on its axis approximately every24 hours◦ Any point on Earth would move through 360

angular degrees in a day’s time or 15 degrees ineach hour

◦Marine ch ron om eter – a relatively accuratetimepiece for determining longitude; developed andperfected by John Harrison


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By international agreement, at the International MeridianConference in 1884, the line passing through the BritishRoyal Observatory at Greenwich, England, called the PrimeMeridian , was designated as the origin for longitude

Longitude position is designated as 0° to 180° east or west

of the Prime Meridian

The 180° meridian provides the basis for the InternationalDate Line,

Unlike the surface distances between lines of latitude,

lines of longitude are unequally spaced◦ At the equator, each degree is 69.2 miles (111.3 km) apart

◦ Con ve rgen ce of Mer id ians : The distance narrows going awayfrom the equator, until all meridians converge at the poles


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Important Properties:1. Scale is the same everywhere on the globe; all great

circles have equal lengths; all meridians are of equallength and equal to the equator; the poles are points.

2. Meridians are spaced evenly on parallels; meridiansconverge toward the poles and diverge toward the

equator.3. Parallels are parallel and are spaced equally on the

meridian.4. Meridians and parallels intersect at right angles.5. Quadrilaterals that are formed between any two parallels

and that have equal longitudinal extent have equal areas.6. The areas of quadrilaterals between any two meridians

and between similarly spaced parallels decreasepoleward and increase equatorward.

map projection 1

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