Test 1 (ch 1-4)
Map Purpose
- Locating points of interest - navigating - compiling complex data - convincing the reader of fact or hypothesis - comparing data - analyzing data
Questions to ask yourself in the design process
- what is the purpose? - who is the audience? - what is the medium? - under what conditions will it be viewed?
Projections
A mathematical conversion of points on the earths surface to a flat plane. Cylindrical, conic, azimuthal
Coordinate space
An agreed upon range of coordinates used to portray the features
Unprojected CS
Based on spherical coordinates, measured in degrees of latitude and longitude.
Projected CS
Converts spherical coordinated to planar coordinates using math equations. Projects 3D coordinates to a 2D map.
Continuous data
Data existing and measurable everywhere, such as temperature or elevation. Consist of rasters
Longitude
Distance east or west of the prime meridian, measured in degrees
Tangent conic
Has one standard parallel
Secant conic
Has two standard parallels
Latitude of origin/reference latitude
Latitude at which the y coordinates equal 0
Nominal data
Names or uniquely identifies objects. Usually portrayed on a single symbol map.
Types of data
Nominal, Categorical, Ordinal, interval, or ratio
Discrete data
Objects exist in a defined and specific location/space, such as houses and roads. Consist of points, lines, and polygons
Standard parallel
Occurs where the projection surface touches the ellipsoid, in the center of tangent projections
Medium
Paper map Electronic files Computer screen Projection screen
Azimuthal projection
Place a plane tangent or secant to the sphere
Oblique cylindrical
Places the line at an angle
Interval data
Places values along a regular numeric scale with no meaningful zero point, ex: elevation. values can be negative.
Ratio data
Places values along a regular scale with a meaningful zero point, ex: population. Cannot be negative.
Transverse cylindrical
Rotating the cylinder sideways that touches the prime meridian
Categorical data
Separates features into distinct categories, ex: rock type. Category names may be text or numeric. Portrayed with a unique values map.
Coordinate system (CS)
The choice of values
Central meridian
The line of longitude in the center of the map, where the x coordinates equal 0.
Source scale
The original scale or resolution the data are captured. Impacts detail and accuracy of the data set.
Extent
The range of x-y values present in the data
Map scale
The ratio of distance on the map to distance on the ground. 1 cm on map = 100,000 cm on ground.
Ordinal data
Type of categorical data, that ranks categories along an arbitrary scale, ex: snail habitats. Based on some quantitative measure.
Types of coordinate systems
Unprojected and projected
Generalization
Used to simplify map feature for clear display. The smaller the map is, the less detailed it will be.
cylindrical projection
Uses a cylindrical surface that touches the earth at the equator
Artistic principles
Visual hierarchy - visual center - rule of thirds - alignment - negative space - size of elements
Map Audience
Who will be viewing the map? What is their expected level of knowledge? Ab the subject and maps Do they have special requirements? Color blindness, large print
Conic projection
based on setting a cone on the sphere
Raster model
designed to store continuous data by breaking a geographic area into small cells or pixels. A single numeric value stored in each.
Vector model
designed to store discrete data using three basic shapes, known as features; points, lines, and polygons
Latitude
distance north or south of the Equator, measured in degrees
Scale range
specifies the range of scales for which the display of the data is valid so that it will only be shown at those scales