Introduction to Coordinate Systems Flashcards
X values
Longitude
Y values
Latitude
What is the Earth’s shape?
Oblate Ellipsoid
Earth rotates on what axis?
Shortest axis, minor axis
Equator is what kind of axis?
Major axis
Earth’s shape is ellipsoid, what other term is also used? Most map project authorities consider both terms correct.
Spheroid
Satellite technology has revealed several elliptical deviations on the earth. The south pole example?
The most southerly point on the minor axis, is closer to the major axis (the equator) than is the north pole, the most northerly point on the minor axis.
Name two common spheroids for North America?
1) Clarke 1866 spheroid and
2) GRS80 spheroid is replacing Clarke 1866
Remember that changing ________ changes the location values for the features that you are mapping. Because of the complexity of changing ________, ground-measured ___________ will remain in use for several years. (same word for all blanks)
Spheroids
Differences in spheroids are not noticeable at scales smaller than what?
1:5,000,000
Every GIS requires at least one _______ system
Coordinate
Two types of coordinate systems used in a GIS?
Geographic coordinate systems and projected coordinate systems
A ________ uses a three-dimensional spherical model to identify points or areas on the surface of the earth. The pairs of coordinate values that identify a feature on a map are relative to its geographic coordinate system. Each coordinate system is commonly illustrated with a network of intersecting lines of latitude (parallels) and longitude (meridians) called the graticule.
Geographic coordinate system
A _______ is based on a geographic coordinate system. They are used to convert feature locations from the spherical earth to a flat map. To do so, latitude and longitude coordinates from geographic coordinate systems are projected to planar coordinates.
Projected coordinate system
True/False: A geographic coordinate system identifies location on a globe using angular degrees rather than linear measurements.
True
At which scale do differences in spheroids generally become visible?
1:5,000,000
True/False: No matter which coordinate system you use, a specific location on the earth will have the same coordinates.
False
True/False: When a more accurate spheroid has been produced, all spatial geodatabases are updated to use the new spheroid.
False
Uses a three-dimensional spherical model to identify points or areas on the surface of the earth. The pairs of coordinate values that identify a feature on a map are relative to its _______?
Geographic coordinate system