A map projection is a transformation applied to a geographic coordinate system (GCS).
There are three main ways to project the 3D oblate spheroid onto a 2D plane.
How/where to reference the surface influences how the map is distorted.
Sometimes also called azimuthal or zenith projections, planar projections are the simplest approach.
The Polar Azimuthal projection, tangent to the north pole.
Conic projections are a great option for the mid-latitudes. They have one central meridian and one/two standard parallel(s).
The BC Environment Albers projection, secant to 50° N and 58° N, central meridian 126° W.
Canada's "official" map projection: Canada Lambert Conformal Conic
A secant conic projection has one standard parallel while a tangent conic projection has two.
The only method that works (well) for displaying the full Earth.
The Mercator projection, tangent to 0° N and, central meridian 0° W.
Transverse cylinders projections are also frequently used.
Some special projections apply more complex transformations.
These tend to be used less frequently.
Which of the these methods for projecting spatial data are best for global scale maps?
All map projections must induce distortions in order to display the 3D earth in 2D, they can cause different distortions in different ways:
All projections require tearing, some projections have more than others.
Shapes and angles are contorted by some, but not all projections.
Areas can be "inflated" or "deflated" some, but not all projections.
All map projections must induce distortions in order to display the 3D earth in 2D. But there are different types of projections that are designed to preserve some attributes.
These projections are designed to maintain the shapes/angles across the map.
These projections are designed to maintain the shapes/angles across the map.
Globe is divided into 60 strips 6° wide, spanning 80°N to 80°S.
A special type of conformal projection.
Vancouver is in UTM Zone 10N.
The Mackenzie Delta, UTM Zone 8N.
These projections are designed to preserves area.
These projections are designed to preserves area.
These projections are designed to preserves distance.
These projections are designed to preserves direction.
These projections are designed for aesthetics.
Minimize distortion without preserving any one property.
A conformal projection will maintain which properties? (select all that apply)
There isn't a "correct" answer here, but there are definitely wrong answers.
Where do the data come from?
What is the map's purpose?
The relationship between distance on a map to distance in the real world.
Small Scale Zoomed out, large area, more generalization, less detail.
Large Scale Zoomed in, small area, more detail, less generalization.
Small Scale 1:10,000,000
1/10,000,000 = 0.0000001
Large Scale 1:1,000
1/1,000 = 0.001
All maps require simplification of real world features. The degree of simplification is a function of the map's scale.
Map scale will impact our choice of projection.
A large scale map shows a _____ area of the earth and small scale map shows a _____ area of the earth.
On a scale of 1 to 5: How do you feel about the lecture topics covered in Module 2 (Steps of Abstraction & Map Projections)?
1 = It makes no sense at all.
3 = Unsure.
5 = I makes perfect sense.
(Participation points only, please answer honestly)
Are there any topics from Module 1 or Module 2 which you would like me to discuss further before moving on to Module 3?