Comprehensive GIS and Cartography: Map Types, Data, and Projections

Cartography

The science or study of making and understanding maps.

Maps

Abstract models of the real world; a symbolic language for describing or communicating about the world; depictions of the spatial arrangement of our institutions.

Marshallese Stick Chart

An example of an early navigational map used by Micronesian peoples to represent ocean currents and islands.

GIS (Geographic Information System)

"A computerized system for capturing, storing, analyzing, visualizing, and managing data that are spatially referenced. The key function is linking LOCATION to INFORMATION."

Vector Data

"A representation of the world using points, lines, and polygons."

Raster Data

A representation of the world as a surface divided into a regular grid of cells.

Feature

"Each geographic object in a vector layer (e.g., city, river, lake, or country)."

Attribute Table

A database table where attributes (identifying and descriptive information) of features are stored.

Layers

"Data organized by theme in GIS (e.g., streets, rivers); one theme per layer."

Data Layers

"Both raster and vector systems have data layers grouped by theme (e.g., streets, rivers, parcels). One theme per layer."

Map Design Principles

"Factors including purpose, geographic space/expanse, available data, map scale, audience, conditions of use, technical limits, and conventions & standards."

Map Composition Elements

"Map body, inset/overview map, title, legend, scale, orientation/direction indicator (north arrow, graticule), and map metadata (source, projection, name, date)."

Visual Hierarchy

The order of graphical representation of map information; helps define figure-ground relationship. First: large masses of color & shape; second: specific information.

Balance

"The organization of map elements and empty space, resulting in visual harmony and equilibrium."

Figure-Ground Relations

Organization used to make objects pop out (figure) or recede into the background (ground).

Typographic Guidelines

"Avoid decorative fonts; use italics for water features; consistency in font type (vary size, not style); legibility (no less than size 7 font); pronounced labels for important features; do not accept default label settings."

Thematic Map

"A map showing the spatial distribution of one or more specific data themes for standard geographic areas (e.g., physical, social, political aspects)."

Spatial Distribution

"The arrangement (spread, pattern) of thematic phenomena in geographic space; can be discrete or continuous, abrupt or smooth."

Levels of Data Measurement

"Nominal (categorization); Ordinal (categorization & ordering); Interval (ordering & explicit values, arbitrary zero); Ratio (ordering & explicit values, non-arbitrary zero)."

Choropleth Mapping

"Portrays data for enumeration units (e.g., counties) using color shading; suited to abrupt data; requires standardization for uneven units."

Proportional Symbol Mapping

Scales symbols proportional to data magnitude; suited to raw data totals; can show multiple variables in graph format.

Isarithmic/Isopleth Mapping

Interpolates isolines between sample points; isopleth uses enumeration units; suited to smooth data totals.

Dot Mapping

"One dot equals a certain amount of phenomena, placed where likely to occur; suited to raw data totals."

Standardization/Normalization

Adjusting raw data totals for the size of enumeration units to allow appropriate comparisons.

Data Classification Methods

Equal Intervals (equal sub-ranges); Quantiles (equal number of observations per class); Natural Breaks/Jenks (natural groupings from histogram); Mean-Standard Deviation (variation from mean); Geometrical Interval (geometrical series minimizing square sum); Manual (user-defined).

Cartogram

"A map where areas are distorted proportional to a variable (e.g., population)."

Bivariate Mapping

Mapping two variables on one map using color blends or symbols.

Quick Review

Spatial Distribution (Review)

"Arrangement of phenomena: discrete/continuous, abrupt/smooth."

Coordinate System

"Reference system for locations; includes geographic (lat/long), projected (2D plane), and grid systems."

Latitude

Angular distance north or south of the equator.

Longitude

Angular distance east or west of a prime meridian.

Datum

Defines position of spheroid/ellipsoid relative to Earth's center.

Map Projection

"Process of transforming spherical Earth to flat map; involves class (cylindrical, conic, planar), case (tangent, secant), aspect (equatorial, polar, oblique)."

Distortion

"Inevitable in projections; affects area, shape, distance, direction."

Geographic Coordinate System

"Global/spherical system using latitude-longitude (e.g., DMS or DD)."

Projected Coordinate System

"Projects Earth's surface onto 2D plane (e.g., using feet/meters)."

Grid System

"Plane/Cartesian (x,y) system over a map projection."

Reference Globe

Reduced-scale model of Earth for projections.

Developable Surface

"Surface (cylinder, cone, plane) onto which graticule is projected."

Distortion Patterns

Vary by projection; minimized along lines of tangency/secancy.

Database

"A set of structured or related data, managing spatial and attribute data in GIS."

DBMS (Database Management System)

"Manages linkages between features and attributes, interactions, versions, integrity, and access."

Attribute Table

"Table with records (rows), attributes (columns), and unique keys."

Query

Method to retrieve data; aspatial (attribute-based) or spatial (location-based).

SQL (Structured Query Language)

"Language for accessing/managing databases using set algebra (<, >, =) and Boolean (AND, OR, NOT)."

Join

Appends attributes from one table to another based on common field (one-to-one or many-to-one).

Relate

Defines relationship between tables without appending (many-to-one or many-to-many).

Primary Key

Unique identifier for each row.

Foreign Key

Non-unique identifier linking to primary key in another table.

Spatial Join

"Joins based on spatial relationships (e.g., intersect, within distance, contains, within)."

Adjacency

Features that touch others.

Containment

Features that contain or surround others.

Model

An idealized and simplified representation of the world.

Data Model

Set of constructs for representing objects and processes in digital environment.

Spatial Data Model

"Constructs for geographical objects, data, processes, and relationships for analysis."

Vector Data Model

"Stores spatial data using coordinate pairs (x,y) for points, lines, arcs, or polygons."

Topology

"Mathematical relationships between points, lines, and polygons; enforces geometric rules (e.g., connectivity, adjacency)."

Raster Data Model

Stores data in grid cells (pixels) with assigned values.

Relational Database Model

"Uses fixed data types (numbers, dates, strings) for attributes; quick but requires modeling."

Object-Oriented Database Model

Models objects after real-world entities.

Object-Relational Database Model

"Blends relational with object-oriented behaviors (e.g., ESRI Geodatabase)."

TIN (Triangulated Irregular Network)

Height observations joined into triangles for elevation modeling.

Network Model

"System of interconnected elements (lines, junctions) for routing analyses."

Modeling Process

"Steps for problem-solving: identify problem, simplify, organize data, flowchart operations, run and modify model."