Transcript What is a coordinate system?

Locating Positions on Earth
• Coordinates are needed to located a fixed
position on Earth.
• Coordinates are two numbers or points on
the Earth’s surface.
What is a coordinate system?
A coordinate system is used for determining
the coordinates of a point .
The most commonly used coordinate system
is the latitude-longitude coordinate system to
locate points on the Earth’s surface.
Latitude and longitude are measure in
angular units: degrees (°) and minutes (΄).
There are 60 minutes in a degree.
What is latitude and what are
the units of measurements?
Latitude is an angular distance north or
south of the equator.
All points that have the same latitude lie on
a circle that is parallel to the equator. These
circles are called parallels of latitude or
parallels.
What is a main line of latitude?
The main line of latitude is called the
equator. The equator is considered to be
the parallel of latitude 0°. Since the lines
are parallel, the never intersect or touch.
Increasing latitude means you are moving
away from the equator!
Decreasing latitude means you are
moving toward the equator!
Understanding latitude!!!
Shown in the figure to the right is
the altitude (angle above the
horizon) to Polaris –the North
Star.
The altitude to Polaris equals the
degree of latitude of the observer
in the Northern Hemisphere.
Be sure to include a north or
south direction when stating the
latitude.
How do you determine the
latitude of a location?
To determine the altitude of
an object in the sky, an
angular-measuring
instrument is used. This is
called a sextant.
In addition: the altitude of
Polaris equals the latitude of
the observer (in the
N.Hemi).
What is longitude and what are
the units of measurement?
Longitude is an angular distance
east or west of the prime meridian.
A meridian of longitude is any
semicircle on Earth’s surface
connecting the north and south
geographic poles.
All longitude lines converge or
come together and intersect at the
poles, like the lines on a basketball.
What is a main line of longitude?
The main line of longitude is called
the prime meridian. The meridian
passes through Greenwich, England.
The other half of the prime meridian is
the international date line (180°).
Any point on the prime meridian has a
longitude of 0°.
Decreasing longitude means you are
moving toward the prime meridian
and away from the 180° meridian.
Increasing longitude means you are
moving away from the prime meridian
and towards the 180° meridian.
Understanding longitude!!!
In writing a location’s longitude, be sure to include a west or
east direction – because that point is either west or east of
the prime meridian.
The hours of the day are based upon the sun’s position in
the sky. Local noon is when the sun is at its highest altitude
in the sky (usually at 12 pm).
We use longitude as a reference to time. If we know that in
24 hours, the earth rotates 360° from west to east, then in
one hour the earth rotates 15° west to east. So technically,
every 15° of longitude, the time changes by an hour.
How do you determine the
longitude of a location?
In order to measure longitude, if you know Greenwich
mean time (GWT – time in Greenwich, England) and your
local time, then you can calculate the time difference in
hours and multiply by 15°.