This exercise will show you how we describe locations on earth with geographical coordinates. You will also learn how to use Google Maps and Google Earth to visualize locations. You should go through the Google tutorial before answering the questions for this asignment. After you have gone through the information, you will be asked to answer some questions to check your skills.

__What are latitude and longitude?__

The
location of any place on the earth's surface can be described by its **latitude**
and **longitude**. The lines that run east and west (left and
right) are the latitude lines and the
lines that run north and south (up and down) are the longitude lines. The
lines are numbered as angles of a sphere measured from the center of the earth.
The latitude measures the angle above or below the equator of a point at the
surface.

The
longitude measures the angle from the ** prime meridian**, which
runs through Greenwich, England.

The
prime meridian was chosen so that the longitudes in Europe would increase
eastward without duplication of values between east and west. The distance
east or west of the prime meridian is measured by angles of 0 to 180 °
E or 0 to 180 ° W.

**°** ) is divided into 60 minutes (symbol
**' **) and each minute is divded into 60 seconds (symbol ").
A given location would be described with degrees, minutes, and seconds of
latitude and **DMS**
system and is the most common system used.

**DD**. Thirty minutes is one half of a
degree, so 45° 30' would be 45.5°

To convert the
DMS 49° 30' 30" to decimal, you would start at the seconds. 30"
/ 60 = 1/2 minute. Add it to the minutes. 30' + **.**5 ' = 30**.**5'
.Now change the minutes to degrees 30.5'/60 = .508 degree so 49° 30' 30"is
49.508 degrees.

__Check
yourself __ Try to answer these questions. You can check your answers by
selecting the link below.

*1.
Suppose we have a location of **
30° 30' 45" N latitude, 90° 50' 30" W longitude .
Which letter is closest to
that location on this globe?*

*2. What
would be the decimal latitude and longitude? *

Note in the globe
diagram that the longitude lines get closer together as you go toward the
poles. This means that a map that uses a even spaced grid causes distortion.
This kind of map is called a Mercator projection and cannot show both the
polar regions because of the distortion. Look at a map that shows Greenland
and Australia. Actually, Australia is 3 times larger
than Greenland but your map may make Greenland look larger.

The Earth is a sphere and since the Earth rotates every 24 hours, when the sun is overhead at noon, the opposite side of the earth is at midnight. Generally, every 15 degrees of longitude is also an hour different in time. Our local time (Central Standard Time) would be different anywhere more than 15 ° away from us. (Daylight savings time causes a shift of 1 hour when it is in effect but the time reference is based on standard time.)

If we want to refer
to an event such as an earthquake, we want to refer to the time so people
anywhere on the globe understand when it was. That international time zone
is called **Universal Coordinated Time** or **UTC**.
UTC uses a 24 hour clock so noon is 12 hours and 3 pm would be 12 + 3 or 15
hours.

UTC was formerly refered to as Greenwich Mean Time or GMT. The UTC is also based on the prime Meridian which runs through Greenwich England. England is at 0 degrees E or W and Chicago is near 90 degrees W so Chicago is one quarter the way around the earth.

That means we are
one quarter of 24 hours or 6 hours different, The earth rotates conterclockwise
as seen from the North pole so London has noon before we do in Chicago. That
is if it is noon in London it is 6 AM standard time in Chicago. (During Daylight
Savings Time we are only 5 hours earlier.)**-** 6

Suppose an earthquake
was reported to have occurred January 29, 2009 at 16:28 UTC.

An excellent reference site for times zones is http://www.worldtimezone.com/time-us24.html

__Check
yourself 3 __*check
your answers here*

*Suppose
it is January 21, 2009 at 10:00 AM in Chicago. What time is it in London?*

**Universal
Transverse Mercator** grid or **UTM**
grid.

In
this grid, the world is divided into 60 north-south **zones**,
each covering a strip 6° wide in longitude. These zones are numbered consecutively
beginning with Zone 1, which is between 180° and 174° west longitude, and
progressing eastward to Zone 60, between 174° and 180° east longitude.

The **zone**
number gives the location. From the diagram above you can see that Chicago
is in zone 16.

The
distance north or (South) from the equator is measured in meters and is called
the **Northing **(or Southing). For instance, 16 359226E 4756749N is a location
in zone 16 that is 4756749 meters North of the equator.

A
line is given down the middle of each zone. A location in the zone is East
of this line or West of this line. The
center line is given a value of 500,000 meters. Distances to the west of this
central meridian are less than 500,000 meters; to the east, more than 500,000
meters.

Our
example location 16 359226E 4756749N is then
in zone 16 and 359226 meters east (actually 140774 meters east of the centerline),
and 4756749 meters north of the equator. This means it is in the west half of zone 16.

This system is pretty awkward
for us but it is very easy for computers. Satellite navigation and GPS usually
convert to degrees, minutes, and seconds. but they actually use the UTM.

**Check
yourself 4 :***check
your answers here*

*Chicago
is in zone 16. Would Hawaii's zone number be greater or less than Chicago's?*

There are a number of places here you can obtain maps online.

You can look up
a location by latitude and longitude in ** Mapquest**
at http://www.mapquest.com/maps/latlong.adp

You can obtain maps from **MSN**
and **MSN virtual earth** at http://maps.live.com/

**Google
maps** are avilable at

**Google Earth**

*You Tube.*

** Check
your self 5**.

*Use
Google Earth and Google maps to answer these questions:*

*What
is located at 36° 46' 56.20" N latitude and 103° 58' 16.27"
W longitude?*