Chp 1 The Earth Flashcards
(33 cards)
Define Ecliptic
The apparent path of the Earth around the Sun
What is the plane of eliptic
The imaginery plane containing the Earths orbit around the sun
What defines the axis of the Earths spin?
The North and South Pole
What is the ICAO standard navigation chart
WGS 84
World Geodetic System 84 - Global reference system
Define Geoid
An irregular shape based on the surface of the oceans, influenced only by gravity and the centrifugal force
Define ellipsoid
The approximation of the Earths shape
What is a geocentric coordinate system
X,Y,Z centered at Earths center of mass
What does the gravitational model do?
Models Earths gravity
Define datum
A way to link mathematical models to real-world locations, used in GPS, mapping, nativgation ect…
What is a negative of modelling the earth as a geoid?
It will always be irregular and complex to model directly as affected by density and topography variations
What are the key characteristics of the WGS84 ellipsoid
It has a semi major axis and also shows flattening
What is the difference between an ellipsoid and a geoid
Geoid undulation
The simplified mathematical approximation vs the true shape of the earth due to gravity
What is a centrifugal force
The apparent force that arises due to the earths rotation around its axis
Where is the centrifugal force the strongest
At the equator as rotational velocity is the highest
What are the two main effects of centrifugal force
Flattening at the poles
Bulging at the equator
These significantly deform the Earth to make it an oblate ellipsoid
How does the centrifugal force effect the geoid model
It redistributed the gravitational potential upon Earth
So we get the flattening at the poles and bulging at the equator
What is the gfs at the equator
9.78m/s^(2)
What is the gfs at the poles
9.83m/s^(2)
What is the great circle
A circle on the surface of the earth that has a radius and center the same as the Earth itself
Between two points on a great circle is the shortest distance across the Earth
What is a small circle
A circle on the surface of the Earth whose center and radius is not the same as the Earth
Define the equator
The main great circle across the Earth that lies in an East-West direction
It divides the Earth into two equal hemispheres
What are the parallels of latitude
They lie in an East-West direction, creating small circles, and are used to define the postition of North/South of the equator
Define rhumb line
A line that cuts all meridians at the same angle, a line of constant direction
Define antimeridian
The meridian which is 180 or directly oppposite to the meridian on the otherside of the Earth
