integrated ch 3 Flashcards
scale
Scale: Measures the proportion of a given distance on a map to the corresponding distance on the ground.
projections
Projections: Methods for turning a 3D globe into a 2D map, involving distortion.
types of map scales
Representative Fraction:
Expressed as a ratio (e.g., 1:25,000).
Numerator is always 1; denominator represents the ground distance.
Graphic Scale:
A scale bar that remains accurate even when resized.
Verbal Description:
Written as a statement (e.g., “1 inch represents 200 feet”).
small vs large scale maps
Small Scale:
Shows a large area with less detail (e.g., 1:1,000,000).
Common for world maps.
Large Scale:
Shows a smaller area with greater detail (e.g., 1:1,000).
Useful for local maps.
extent vs resolution
Extent
The area visible on the map.
Example: National extent vs. state-level extent.
Resolution
The smallest unit that is mapped.
Example: A map showing counties (resolution) across the United States (extent).
coordinate systems
Cartesian Coordinate System
Grid-based system with an x (horizontal) and y (vertical) axis.
Origin (0,0) is the reference point.
Geographic Coordinate System
Accounts for Earth’s spherical shape.
Longitude: Measures east-west position.
Latitude: Measures north-south position.
Reference lines:
Prime Meridian (0° longitude).
Equator (0° latitude).
map projections
Map Projections
Purpose
Convert a 3D globe to a 2D surface while preserving specific map properties.
Developable Surfaces
Plane (planar projection): Best for polar regions.
Cone (conic projection): Suitable for mid-latitudes.
Cylinder (cylindrical projection): Works well for equatorial regions.
Tangent Point/Line
The place where the developable surface touches the globe.
Minimal distortion occurs here.
types of projections
Conformal:
Preserves shape and angles.
Example: Mercator projection (used for navigation).
Distorts area, especially near the poles.
Equal Area:
Preserves area but distorts shape.
Example: Gall-Peters projection (used for density mapping).
Equidistant:
Preserves distances along specific lines.
Example: Azimuthal Equidistant projection (used for flight paths).
Compromise:
Balances distortions of shape, area, and distance.
Example: Robinson projection (used for world maps).
Interrupted:
Reduces distortion by “tearing” the map in less critical areas.
Example: Goode Homolosine projection (used for global area relationships).
Artistic:
Focuses on aesthetic appeal rather than accuracy.
Example: Stabius-Werner projection.
distortions in projections
-Properties Affected by Distortion
Shape (Conformal maps preserve this).
Area (Equal Area maps preserve this).
Distance (Equidistant maps preserve this).
Direction (Azimuthal maps preserve this).
-Trade-Offs in Projections
No projection can preserve all properties simultaneously.
Choice depends on the map’s purpose.
applications of use cases
Examples of Use Cases
Navigation:
Conformal maps (e.g., Mercator) for accurate angle measurements.
Density Analysis:
Equal Area maps (e.g., Gall-Peters) for comparing land masses.
Distance Mapping:
Equidistant maps (e.g., Azimuthal Equidistant) for flight paths.
What is a tangent point in map projections?
Answer: The point where the projection surface touches the globe, minimizing distortion.
What is the difference between small-scale and large-scale maps?
Answer:
Small-scale: Covers large areas with less detail (e.g., 1:1,000,000).
Large-scale: Covers small areas with more detail (e.g., 1:1,000).
Why is scale critical in mapmaking?
Answer: It determines the level of detail and the extent of area covered.
What is the primary purpose and example of a conformal projection?
to preserve shape and angles
-e.g. mercator projection, used for navigation
equal area projection and example
-preserves area and distorts shape
-e.g. gall-peters projection, used for density mapping
