Summary
Highlights
The lecture begins by introducing thematic maps, which display specific data. These can be qualitative, showing the distribution of categories (e.g., oil fields, libraries), or quantitative, illustrating numerical data (e.g., population density). Various symbol types are used, including point symbols (dots, triangles) for discrete features, dot maps where each dot represents a quantity, and graduated symbol maps where symbol size varies by quantity.
Area symbols color regions based on features, applicable to both qualitative (e.g., religion, language) and quantitative data. Choropleth maps, also known as graduated color maps, group data into classes represented by distinctive colors or shades to show how amounts vary geographically, such as population density by county.
Cartograms distort geographical areas based on a specific variable, such as population, altering shapes, distances, and directions to visually represent data. The lecture highlights three problems with area-based maps: they can imply uniformity where variation exists, suggest abrupt changes where they are gradual, and poorly chosen colors can imply disproportionate importance.
Line symbols represent features with length but insignificant width, like roads or political boundaries. Isolines, such as contour lines on topographic maps, connect points of equal value (e.g., elevation, temperature). Flow line maps depict movement between places, with arrows indicating direction and line width varying to represent quantity (e.g., migration, traffic).
Maps can be intentionally misused to convey a specific bias, through techniques like omitting scales, using impactful colors, or distorting symbols. Examples include Nazi propaganda maps seeking sympathy and various electoral maps that display results by state or county, often misleadingly emphasizing certain regions without accounting for population density. Cartograms of election results visually adjust state or county sizes by population or electoral votes, offering a more representative view of voter distribution.
The lecture introduces spatial technologies, starting with remote sensing, which gathers information about Earth's surface without direct contact, including aerial photography and non-photographic imagery like infrared or radar. Global Navigation Satellite Systems (GNSS), known as GPS in the US, use orbiting satellites to transmit positioning data, enabling accurate location (latitude, longitude, altitude) for various applications, from navigation to environmental assessment.
GIS is a computer-based system for assembling, storing, manipulating, analyzing, and displaying geographically referenced data. It involves five components: data input, management, manipulation, analysis (to find patterns), and output. GIS creates geographic databases by tying data to precise geographical locations, allowing for complex spatial analysis and the creation of layered maps for diverse applications in fields like biology, epidemiology, governmental planning, and business.