7/24/2019 LOCATIONAL SETTINGS.docx

http://slidepdf.com/reader/full/locational-settingsdocx 1/5

LOCATIONAL SETTINGS

A location is the place where a particular point or object

exists. Location is an important term in geograph! an" isusuall consi"ere" more precise than #place.# A localit is a

human settlement$ cit! town! %illage! or e%en archaeological

site.

Locational settings $

A location in the earth can be locate" b latitu"es &

longitu"es. This locational setting is "one b Geographiccoor"inate sstem. A geographic coor"inate sstem is

a coor"inate sstem that enables e%er location on the Earth to

be speci'e" b a set o( numbers or letters. The coor"inates are

o(ten chosen such that one o( the numbers represents %ertical

position! an" two or three o( the numbers represent hori)ontal

position. A common choice o( coor"inates

is latitu"e! longitu"e an" ele%ation.

A geographic coordinate system (GCS) uses a three-dimensional

spherical surface to define locations on the earth. A GCS is often incorrectly

called a datum, but a datum is only one part of a GCS. A GCS includes an

angular unit of measure, a prime meridian, and a datum (based on a spheroid).

A point is referenced by its longitude and latitude values. Longitude and

latitude are angles measured from the earths center to a point on the earths

surface. !he angles often are measured in degrees (or in grads). !he follo"ing

illustration sho"s the "orld as a globe "ith longitude and latitude values.

7/24/2019 LOCATIONAL SETTINGS.docx

http://slidepdf.com/reader/full/locational-settingsdocx 2/5

#n the spherical system, hori$ontal lines, or east%"est lines, are lines ofe&ual latitude, or parallels. 'ertical lines, or north%south lines, are lines of e&ual

longitude, or meridians. !hese lines encompass the globe and form a gridded

net"or called a graticule.

!he line of latitude mid"ay bet"een the poles is called the e&uator. #t

defines the line of $ero latitude. !he line of $ero longitude is called the prime

meridian. or most geographic coordinate systems, the prime meridian is the

longitude that passes through Green"ich, *ngland. +ther countries use

longitude lines that pass through ern, ogota, and aris as prime meridians.

!he origin of the graticule (,) is defined by "here the e&uator and prime

meridian intersect. !he globe is then divided into four geographical &uadrants

that are based on compass bearings from the origin. /orth and south are above

and belo" the e&uator, and "est and east are to the left and right of the prime

meridian.

!his illustration sho"s the parallels and meridians that form a graticule.

Latitude and longitude values are traditionally measured either in decimal

degrees or in degrees, minutes, and seconds (01S). Latitude values are

measured relative to the e&uator and range from -23 at the South ole to 423

at the /orth ole. Longitude values are measured relative to the prime meridian.

!hey range from -563 "hen traveling "est to 563 "hen traveling east. #f the prime meridian is at Green"ich, then Australia, "hich is south of the e&uator

7/24/2019 LOCATIONAL SETTINGS.docx

http://slidepdf.com/reader/full/locational-settingsdocx 3/5

and east of Green"ich, has positive longitude values and negative latitude

values.

#t may be helpful to e&uate longitude values "ith 7 and latitude values

"ith 8. 0ata defined on a geographic coordinate system is displayed as if a

degree is a linear unit of measure. !his method is basically the same as the lateCarr9e pro:ection.

Although longitude and latitude can locate e;act positions on the surface

of the globe, they are not uniform units of measure. +nly along the e&uator does

the distance represented by one degree of longitude appro;imate the distance

represented by one degree of latitude. !his is because the e&uator is the only

 parallel as large as a meridian. (Circles "ith the same radius as the spherical

earth are called great circles. !he e&uator and all meridians are great circles.)

Above and belo" the e&uator, the circles defining the parallels of latitudeget gradually smaller until they become a single point at the /orth and South

oles "here the meridians converge. As the meridians converge to"ard the

 poles, the distance represented by one degree of longitude decreases to $ero. +n

the Clare 56<< spheroid, one degree of longitude at the e&uator e&uals 555.=>5

m, "hile at <3 latitude it is only ??.6> m. ecause degrees of latitude and

longitude dont have a standard length, you can@t measure distances or areas

accurately or display the data easily on a flat map or computer screen.

 Tpes o( Location $

 Absolute Location

Absolute location "escribes the location o( a place base"

on a 'xe" point on earth. The most common wa is to i"enti(

the location using coor"inates such aslatitu"e an" longitu"e.

 Lines o( longitu"e an" latitu"e crisscross the earth.

Latitude is used to mar the north-south position of a location on the *arth@ssurface and ranges from degrees at the e&uator to 2 degrees at the /orth and

South oles. !here are 56 degrees of latitude and the distance bet"een each

degree of latitude is roughly <2 miles (555 m).

7/24/2019 LOCATIONAL SETTINGS.docx

http://slidepdf.com/reader/full/locational-settingsdocx 4/5

An e;ample of an absolute location using latitude and longitude is

the nited States Capitol "hich is located at =63 ?=B =? /, DD3 B => E.

 Latitude is al"ays "ritten first and latitude and longitude are composed of

degrees, minutes, and seconds (01S).

Absolute location can also refer to an address, the street address of the S

State Capitol is irst St S* in Eashington, 0C >F. #n both instances,absolute location refers to a fi;ed point based on an abstract net"or of

imaginary locations.

Relative Location

elative location refers to the position of a place or entity based on its

 positive "ith respect to other locations. or e;ample, the location of the S

Capitol is located about =6 miles south"est of altimore. elative location can

 be e;pressed in terms of distance, travel time, or cost.

elative location can also be used to provide geographic conte;t. or

e;ample, overvie" or locator maps sho" the relative location of a place or

entity based on a larger geographic vie". or e;ample, the inset map belo",

sho"s the relative location of the state of !e;as "ithin the nited States.

7/24/2019 LOCATIONAL SETTINGS.docx

http://slidepdf.com/reader/full/locational-settingsdocx 5/5