Latitude and Longitude
It’s a “coordinate system” (uses 2
points). It is designed to help find your
place on earth. Latitude and longitude
are measured in degrees.
Latitude
► Run
parallel (even with) the equator.
► Used to show how far north or south of the
equator you are.
► Lines of latitude never cross each other.
► All latitude lines must be labeled North or
South.
Polaris: The north star
► In
the northern hemisphere (where we live),
the angle of Polaris above the horizon is =
the latitude at that place.
Examples:
Examples continued
Longitude
► Measures
east/west locations. All longitude
lines must be labeled as either East or West.
► Longitude lines run next to each other in a
north/south manner, and they all come
together at the poles.
► Longitude lines are called Meridians.
► 0 degrees longitude is called the prime
meridian, and passes through Greenwich
England.
Longitude Continued
► The
opposite of that is 180 degrees
longitude. It’s called the international
dateline, and found in the middle of the
pacific ocean.
Let’s put it all together
Back to Polaris: How can we
measure its Altitude??
► The
altitude of Polaris (as well as anything
else in the sky) can be measured using an
Astrolabe.
► As you look up, the string will fall straight,
and show you what your angle is.
Using an Astrolabe
Latitude/Longitude and New York
State
► New
York State falls in the North West
section of the planet, so all it’s latitudes are
North and its longitudes are West.
► Latitudes 40* 30’ to 45*.
► Longitudes 72* to 79* 45’.
► Degrees are further broken into minutes (‘)
and seconds (“). Remember 60 minutes per
degree, and 60 seconds per minute, just like
time.
Longitude and Time
► The
earth rotates (makes the sun appear to move)
at 15 degrees per hour.
► Time starts at the Prime Meridian, known as
Greenwich Mean Time (GMT).
► If you know the time where you are, and the time
in Greenwich, then you can find your longitude.
Example, in NY we are 5 hours behind GMT (15* x
5 hours = 75*). Take our time here and add 5
hours, that gives you GMT.
► See page 18 in the reference tables for more!!!!
Longitude and time problems
► If
the time is 5pm in NY, what time is it in
Greenwich?
► 5pm + 5 hours = 10pm.
► If the time is 6am in NY, what is the time in
California? (California is 45* west of NY).
► 45*/15*per hour = 3 hours behind. So, 6am
– 3 hours = 3am.
Longitude and time problems
► What
is the time difference between 30*W
longitude and 75*W longitude?
► 75*-30*=45*. 45*/15*per hour = 3 hours.
► If the time in Austin Texas (90*W) is 4pm,
what is the time in Greenwich?
► 90*-0*=90*. 90*/15*per hour = 6 hours.
4pm + 6 hours = 10pm GMT.