Basic Coordinate Systems Flashcards
Definitions
What enables geographic datasets to use common locations for integration?
Coordinate System
Definitions
A reference system used to represent the locations of geographic features, imagery, and observations such as GPS locations within a common geographic framework
Coordinate System
Definitions
- The network of intersecting lines of latitude and longitude
- It is imaginary on the Earth but is drawn on globes and maps for reference
Graticule
In 1878, Canadian Sir Sanford Fleming, proposed a system of worldwide ________ based on lines of longitudes
(Two words, similar to the name of an arcade)
Time Zones
The earth was divided into ____ time zones using zones of longitude which were 15 degrees wide
24
Definitions (The shape of the earth)
- Defined as the surface of the earth’s gravity field, which is approximately the same as mean sea level
- The mass of the earth is not uniform at all points and the direction of gravity changes, hence the shape is irregular
(Weird ahh spelling)
Geiod
Definitions (The shape of the earth)
________ is the simplest approximation of the Earth’s surface and radius is constant
Sphere
Definitions (The shape of the earth)
- The Earth is flattened at the poles and bulges at the equator due to its revolution
- Mathematical approximation of the shape of the Earth
Ellipsoid/Spheroid
Rotating the ellipse around the semi minor axis creates a spheroid and also known as oblate ________
Ellipsoid
Definitions (The shape of the earth)
Is built on top of the selected spheroid and can incorporate local variations in elevation
Datum
While spheroid approximates the shape of the Earth, a datum defines the position of the ________ relative to the center of the Earth
Spheroid
When a datum is created to suit a particular country or region, ellipsoid/spheroid is positioned so that it best matched the ________ of the country
Geiod
True or False
The coordinate system origin of a local datum is not at the center of the Earth
True
Definitions (The shape of the earth)
Provides a frame of reference for measuring locations on the Earth’s surface and is usually defined by latitude and longitude lines
Datum
Definitions
Best earth-fitting spheroid which relates coordinates to the Earth’s center of mass
Geocentric Datum
Use of local datums results to ________ lines of longitude and latitude between different countries or regions
Uneven
A ________________ (GCS) uses a three-dimensional spherical surface to define locations on the earth
Geographic Coordinate System
A ________________ (PCS) is defined on a flat, two-dimensional surface
Projected Coordinate System
Definitions
Is a system of mathematics and geometry whereby the information on the surface of a sphere (the Earth) is transferred onto a flat piece of paper (a map)
(Hint: MP)
Map Projection
Definitions
- This describes the way an imaginary piece of paper is laid on the Earth to obtain the latitude and longitude for the map
- Where the imaginary ‘piece of paper’ touches the Earth, there is no distortion on the map but as you move away, distortion increases
Basic Projection Techniques
- It has constant lengths, angles and areas across the two dimensions
- A ________ is always based on a geographic coordinate system that is based on a sphere or spheroid
Projected Coordinate System (PCS)
- A ________ includes an angular unit of measure, a prime meridian, and a datum (based on spheroid)
- A point is referenced by its longitude and latitude
Geographic Coordinate System (GCS)
Definitions
- Is the center line of longitude of projection systems projection systems use line of longitude like the prime meridian that splits east and west, central meridian do the same thing
- UTM zone uses the central meridian as an origin of X-coordinates (eastings)
- Central meridian is assigned a value of 500,000 m (false easting)
Central Meridian
Three types of Cylindrical Projection
- Cylindrical Projection - Mercator
- Cylindrical Projection – Transverse Mercator
- Cylindrical Projection – Universal Transverse Mercator
What are the three basic projection techniques?
- Azimuthal Projection
- Conical Projection
- Cylindrical Projection
What are the eight elements of a latitude?
- Latitude
- Parallel
- Equator
- Pole
- Arctic Circle
- Antarctic Circle
- Tropic of Cancer
- Tropic of Capricorn
What are the three elements of a longitude?
- Longitude
- Meridian
- Prime Meridian (Greenwich)
Two examples of local or regional datum
- Luzon 1911
- PRS 1992
Two examples of geocentric datum
- WGS 1984
- GRS 1980
