Latitude and Longitude:Finding Locations on

Planet Earth.

With thanks and credit to Step.com

Typical Graph

This is an example ofa typical graph.

It is made up of pointsthat are connected bya line.

Typical GraphY axis

X axis

Each point has two values:

An ‘X’ value that runs alongthe horizontal ‘X’ axis and.......

A ‘Y’ value that runs alongthe vertical ‘Y’ axis

Each point is expressed as an X value and a Yvalue with the X value written first. For example...

(4,7)

and...........

7,5)

Typical Graph

X

Y

(-X,+Y)

(+X,-Y)

(+X,+Y)

(-X,-Y)

Graphs may be dividedinto quadrants with theX and Y values beingeither positive (+) ornegative (-) dependingon the quadrant in whichthey are located.

Now let’s apply the sameprinciples to latitude andlongitude.

On the map horizontal linesare lines of latitude and....

vertical lines are lines oflongitude.

The X axis is the equator

and the Y axis which runsthrough Greenwich, Englandis the Prime Meridian.Equator

Prime Meridian

Any location north of the equator is a NORTH LATITUDE

Any location south of the equator is a SOUTH LATITUDE

Any location west of the prime meridian is a WEST LONGITUDE

Any location east of the prime meridian is an EAST LONGITUDE

We can divide the Earth into quadrants: NE where alllatitudes are NORTH and all longitudes are EAST.

We can divide the Earth into quadrants: SE where alllatitudes are SOUTH and all longitudes are EAST.

We can divide the Earth into quadrants: SW where alllatitudes are SOUTH and all longitudes are WEST.

We can divide the Earth into quadrants: NW where alllatitudes are NORTH and all longitudes are WEST.Notice that EVERY point in the United States will have a NORTHlatitude and a WEST longitude since we are in the NW quadrant.

90°S

90°N What is latitude?Latitude is the distancefrom the equator along theY axis. It is expressed in degrees.The north pole is 90° NThe south pole is 90° SAnd remember that theequator is 0° latitude.

What is the maximum possible latitude on Earth? 90° is maximum. You could be at 90°N or 90°S butthere is no greater latitude on Earth (or anywhere else)

0°

What is longitude?Longitude is the distancefrom the prime meridianalong the X axis.Just like latitude, longitudeis measured in degrees.The prime meridian is 0°

0°

And if you go half wayaround the world you willreach the 180° longitudeline.180° 180°

Understand that there aren’t two 180° lines. On this FLAT map it just looks that way. It’s the SAME line.What is the maximum possible longitude on Earth?180° is the maximum possible longitude on Earth.

Each box on this map is 15°. With that in mind how can we identify specific locations(red dots)? Remember, write latitude first!What are the coordinates of location......A

60°N, 30°W

What are the coordinates of location......B

15°S, 105°W

What are the coordinates of location......C

75°S, 75°E

But what about location D ? It’s in the middle of a box. What do we do now?

Prime meridianInternational Date line

Equator

Northern Hemisphere

Southern Hemisphere

WE

Reference Table Page 5-Tectonics Plate Map 7min.flv

60’

60’

Let’s use an example from the referencetables (page 3). Look at Ithaca, NY.

Ithaca

The latitude is morethan 42°N

42°N

but less than 43°N

43°N

and the longitude ismore than 76°W

76°W

but less than 77°W

77°W

Each degree is about 111 kilometers so the yellow-shadedbox (1° x 1°) in which Ithaca is located covers over 12,000square kilometers of land.We need to be more precise. We can do that by subdividingeach degree into 60 smaller units called minutes.

If there are 60minutes in eachdegree then halfa degree wouldbe 30 minutes.Let’s draw in the 30 minute (30’)line.

See these 2 marks?They are half way(30’) between 42°N and 43°N.Using a ruler,connect them.

The line you just drew is 42°30’N. Now let’s look at lines of longitude.See these 2 marks? They are half way (30’) between 76°W and 77°W.Using a ruler, connect them.The line you just drew is 76°30’W.Now let’s see if we can locate Ithaca more precisely.

First comes latitude.Notice that Ithaca isjust south of the42°30’N line. If it’snot quite 30’ thenlet’s call it 25’.Ithaca is located 42°25’N.

Now we’ll do longitude which, for Ithaca is easy since it’s located righton the 76°30’W line. Ithaca’s longitude is 76°30’W.Now we’ll put latitude and longitude together to give a precise location:Ithaca is 42°25’N , 76°30’W.Let’s try another............................

Let’s find thelocation of Plattsburgh, NYto the nearest minute.First draw the44°30’ lineThen, the 73°30’line.Now let’s try toestimate thelocation.

Plattsburgh is more than 44°30’N but less than 45°N. A good estimatewould be 44°40’N.Plattsburgh is more than 73°W but less than 73°30’W. A good estimatewould be 73°25’WPutting the two together, Plattsburgh is about 44°40’N, 73°25’W.

Here are some things to remember:> Latitude is written first and must always include N (north) or S (south) of the equator.> Longitude is written next and must always include E (east) or W (west) of the prime meridian.> All latitudes in New York State are N (north), and all NYS longitudes are W (west). > Each degree of latitude or longitude can be divided into 60 minutes. > A minute, as used here, is a unit of distance on the earth’s surface. It is not a unit of time.

> The map on page 3 of your reference tables is small and it is impossible to be absolutely precise. Your best estimate should be to the nearest 5 or 10 minutes. In other words, an estimate of 73°25’W is OK but 73°28’W is trying to be more accurate than is reasonably possible with this map.> As with anything else you learn you will get better with practice.........

SO PRACTICE, PRACTICE, PRACTICE!