Creating a Flat Earth Image Flashcards
(38 cards)
What is the difference between graticule and grid
Graticule Latitude and longitude is an example. For grid X/Y coordinates is an example.
Transverse
Rotated cyclindar 90 degrees
Developable Surface:
A geometric shape such as a cone, or cylinder, that can be flattened without being distorted. Many map projections are classified in terms of these shapes.
Cylindrical Projection
Cylindrical projections result from projecting a spherical surface onto a cylinder. Can be tangent or secant. A secant cylindrical projection has 2 lines of intersection between the cylinder and the globe both are small circles. When the cylinder is tangent to the sphere contact is along a great circle (the circle formed on the surface of the earth by a plane passing through the center of the earth. Cylinder is a good projection for wanting all of earth! The end result is a rectangular map!
Conic Projection
Conic projections result from projecting a spherical surface onto a cone. When the cone is tangent to the sphere, contact is along a small circle. In the secant case the cone touches the sphere along 2 lines, one great circle and the other a small circle. Not a good projection if wanting to map all of earth. Great for one of the poles.
Planar Projection:
Results from projecting a spherical surface onto a plane. When the plane is tangent to the sphere contact is at a single point on the surface of the earth. In the secant case the plane touches the sphere along a small circle if the plane does not pass through the center of the earth when it will touch along a great circle.
Line of Tangency
When a developed surface comes into contact with the globes surface along a single line the projection is considered to be tangent. (the projection surface is tangent to the globes along that line).
Line of Secancy
When a developed surface comes into contact with the globes surface along 2 lines, the projection is considered to be secant! ( the surface cuts through the surface of the globe)
Secant Cylindrical Projection:
the cylinder touches the sphere along 2 lines, both small circle (a circle formed on the sruface of the earth by a plane not passing through the center of the earth)
Tangent Cylindrical Projection:
Contact is along a great circle (the circle formed on the surface of the earth by a plane passing through the center of the earth)
What happens when the cylinder upon which the sphere is projected is at a right angle to the poles?
The cylinder and resulting projection is transverse! When the cylinder is at some other non-orthgonal angle with respect to the poles the cylinder and resulting projection is oblique.
When the cone is tangent to the sphere, contact is along what?
A small circle!
When the cone is secant to the sphere the cones touches the sphere along….
2 lines! one a great circle and the other a small circle.
In a planar projection what happens when the plane is tangent to the sphere?
The contact is at a single point on the surface of the earth.
In a planar projection what happens when the plane is secant to the sphere?
The plane touches the sphere along a small circle if the plane does not pass through the center of the earth, when it will touch along a great circle.
What are the different types of light sources?
- ) Orthographic: Infinite light source. A view of the world from a vetical perspective. As if you were looking at it at the entire earth from directly above the surface.
- ) Stereographic: Light source at antipode
- ) Gnomic: Light source at center of globe. Map projection with a theoretical
Equation for Scale Factor
Actual scale/Principal Scale= Scale Factor
Scale factor is used for
Understanding the amount of distortion on the map
Lambert Azimuthal Equal Area is a product of….
Planar surface
mercator projection is also a
cylindrical projection
If we move away from a standard line does distortion increase or decrease?
It increases!
What does a conformal map preserve?
Shape preservation
What does a Equidistant Map Preserve?
Distance
What does a Azimuthal Map Preserve?
Direction
