Coordinate Systems Flashcards
What is the best model of the Earth?
A globe since it has the only true scale
What are the Three types of Coordinate Systems?
- Rectangular (Cartesian)
- Geographic
- Astronomic
What is the purpose of the Coordinate systems?
- simplify the earths surface
- surveying applications
- naviagtion
Who created the rectangular coordinate system?
Rene Descartes
What is Geographical Coordination
- Define position and Orientation, relative distance between two points
- Equator: formed by the intersection of a right angle to the axis of rotation
- Meridians: formed by vertical planes passing through the center. (0-180d)
- Parallels: 0-90d
- Latitude(n,s) and longitude(e,w) are points from the centre of the earth
Where is the Prime Meridian Located?
Greenwich, England
Astronomical Coordinates
- early form of mapping
- determined on a celestial sphere with Earth at the centre
What is a Map Projection?
a method for mapping spatial patterns from a curved surface to a flat surface.
What are some valuable properties of a map? (SADD)
- Shape
- Area
- Distance-(Scale of distances)
- Direction-(Compass Directions)
What is Conformal?
When a map preserves shape over a small area. Means “right” in Greek
What are three surfaces you can project a map on?
Plane, Cone and Cylinder
On a plane projection map, what are three possibilities for the projection centre?
- Gnomonic (oldest map Projection)
- Stereographic
- Orthographic
Gnomonic Projection:
-projection from centre of the earth onto the plane
- Great circles show up as straight lines
- (Will look like a compass)
Stereographic Projection:
- Projection center opposite to the point of plane tangency. (projects through the earth onto a plane)
- (will look like a stretched bed sheet at the corners)
Orthographic:
- Projection centre at infinity
- (projected from the edges of the earth)
- (will look like a circle with a straight line down the centre and curved lines radiating outwards)
What are the two types of conical map projections? (light still projected from centre of earth)
- Secant (cone that passes through the edges of the earth)
- Tangent (cone that sits on top of the sphere, does not enter the surface)
Tangent Conical Maps:
- STANDARD PARALLEL: to scale where the cone would touch the surface, distorts as you move away from this point.
- As the height of the cone increases, the standard parallel moves closer to equator
- When standard parallel reaches the equator it becomes a cone, when it hits the north pole it becomes a plane
Secant (Lambert Conformal Conic):
- has 2 standard parallels since it passes through the surface of the globe that intersect at 1/6 of distance of top and south of map.
- Parallels: arcs of concentric circles with centre at apex
- Meridians: straight lines
- Scale true at both standard parallels
Mercator Map Projection:
- will look like a stretched grid map, shows a constant bearing. These are called rhumb lines or loxodrome
- Meridians have equal spaced lines, while the parallels are horizontal lines whose spacing increases towards the poles
Universal Transverse Mercator Map Projection (UTM):
- Similiar to the Mercator map but the projection is rotated 90d.
- looks like 4 ellipsoids, two from the poles and two from the equator.
- Can have one or two meridians with true scale
- projection zones are 6d wide
What shape is the Earth?
An oblate ellipsoid and also a spheroid
What Axis does the Earth rotate about?
Its short Axis (Minor Axis)
