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CV-21 - Map Reading

Map reading is the process of looking at the map to determine what is depicted and how the cartographer depicted it. This involves identifying the features or phenomena portrayed, the symbols and labels used, and information about the map that may not be displayed on the map. Reading maps accurately and effectively requires at least a basic understanding of how the mapmaker has made important cartographic decisions relating to map scale, map projections, coordinate systems, and cartographic compilation (selection, classification, generalization, and symbolization). Proficient map readers also appreciate artifacts of the cartographic compilation process that improve readability but may also affect map accuracy and uncertainty. Masters of map reading use maps to gain better understanding of their environment, develop better mental maps, and ultimately make better decisions. Through successful map reading, a person’s cartographic and mental maps will merge to tune the reader’s spatial thinking to the reality of the environment.

CV-11 - Common Thematic Map Types

Thematic maps cover a wide variety of mapping solutions, and include choropleth, proportional symbol, isoline, dot density, dasymetric, and flow maps as well as cartograms, among others. Each thematic map type requires a different data processing method and employs different visual variables, resulting in representations that are either continuous or discrete and smooth or abrupt. As a result, each solution highlights different aspects of the mapped phenomena and shapes the message for the map readers differently. Thematic maps are tools for understanding spatial patterns, and the choice of thematic map type should support this understanding. Therefore, the main consideration when selecting a thematic map type is the purpose of the map and the nature of the underlying spatial patterns.

This entry reviews the common types of thematic maps, describes the visual variables that are applied in them, and provides design considerations for each thematic map type, including their legends. It also provides an overview of the relative strengths and limitations of each thematic map type.

CV-01 - Cartography and Science

"Science" is used both to describe a general, systematic approach to understanding the world and to refer to that approach as it is applied to a specific phenomenon of interest, for example, "geographic information science." The scientific method is used to develop theories that explain phenomena and processes. It consists of an iterative cycle of several steps: proposing a hypothesis, devising a way to make empirical observations that test that hypothesis, and finally, refining the hypothesis based on the empirical observations. "Scientific cartography" became a dominant mode of cartographic research and inquiry after World War II, when there was increased focus on the efficacy of particular design decisions and how particular maps were understood by end users. This entry begins with a brief history of the development of scientific cartographic approaches, including how they are deployed in map design research today. Next it discusses how maps have been used by scientists to support scientific thinking. Finally, it concludes with a discussion of how maps are used to communicate the results of scientific thinking.

DM-85 - Point, Line, and Area Generalization

Generalization is an important and unavoidable part of making maps because geographic features cannot be represented on a map without undergoing transformation. Maps abstract and portray features using vector (i.e. points, lines and polygons) and raster (i.e pixels) spatial primitives which are usually labeled. These spatial primitives are subjected to further generalization when map scale is changed. Generalization is a contradictory process. On one hand, it alters the look and feel of a map to improve overall user experience especially regarding map reading and interpretive analysis. On the other hand, generalization has documented quality implications and can sacrifice feature detail, dimensions, positions or topological relationships. A variety of techniques are used in generalization and these include selection, simplification, displacement, exaggeration and classification. The techniques are automated through computer algorithms such as Douglas-Peucker and Visvalingam-Whyatt in order to enhance their operational efficiency and create consistent generalization results. As maps are now created easily and quickly, and used widely by both experts and non-experts owing to major advances in IT, it is increasingly important for virtually everyone to appreciate the circumstances, techniques and outcomes of generalizing maps. This is critical to promoting better map design and production as well as socially appropriate uses.

CV-08 - Symbolization and the Visual Variables

Maps communicate information about the world by using symbols to represent specific ideas or concepts. The relationship between a map symbol and the information that symbol represents must be clear and easily interpreted. The symbol design process requires first an understanding of the underlying nature of the data to be mapped (e.g., its spatial dimensions and level of measurement), then the selection of symbols that suggest those data attributes. Cartographers developed the visual variable system, a graphic vocabulary, to express these relationships on maps. Map readers respond to the visual variable system in predictable ways, enabling mapmakers to design map symbols for most types of information with a high degree of reliability.

DC-42 - Changes in Geospatial Data Capture Over Time: Part 2, Implications and Case Studies

Advances in technological approaches and tools to capture geospatial data have contributed to a vast collection of applications and enabled capacity for new programs, functions, products, workflows, and whole national-level spatial data infrastructure. In this entry, such outcomes and implications are described, focusing on developmental changes in specific application areas such as land use & land cover inventory, land parcel administration, and business, as well as examples from federal agencies, including the US Geological Survey, the Census Bureau, US Fish and Wildlife Service, and the US Department of Agriculture. These examples illustrate the diverse ways that the dramatic changes in geospatial data capture methods and approaches have affected workflows within agencies and have spatially empowered millions of users and the general public. For additional information on specific technical changes, see Part 1: 

DA-31 - GIS&T and Libraries, Archives, and Museums

Libraries, archives, and museums (LAMs) are an important part of the GIS&T ecosystem and they engage in numerous activities that are critical for students, researchers, and practitioners. Traditionally these organizations have been at the forefront of developing infrastructures and services that connect researchers and others to historical and contemporary GIS data, including print maps. More recently, as a result of greater interest in spatial thinking and research, these organizations and institutions have become a place for instruction, outreach, and practice. This entry will discuss the historical role that LAMs have played in supporting and developing GIS&T as well as focus on current trends.

GS-26 - Mapping Spatial Justice for Marginal Societies

Marginal populations are those populations that are often overlooked by government, dependent upon non-governmental aid, and lack access to basic resources such as water, food, shelter, and security.  However, these groups are increasingly included in partnerships to map their resources (or lack thereof), develop basic applications in geospatial data collection, and devise innovative approaches to participatory mapping using geospatial technologies to address local and regional problems. Rapid technological changes and increased access to mobile geospatial tools enhance data creation efforts to map marginal populations and identify their needs. However, such mapping activities reveal fundamental inequities in collecting, disseminating, and visualizing spatial data.  This chapter defines marginal populations and provides an overview of data needs, geospatial tools, and ethical obligations necessary for these partnerships.

CV-42 - Collaborative Cartography

Collaborative cartography is a newly emerging approach for engaging community-centered processes of map production to represent harm caused by oppressive systems and pathways for healed futures. While mapping has a long history of engagement in activist movements, community involvement is often segmented to considerations determining the topic of the map and the subsequent supporting data-collection/validation processes. Collaborative cartography, however, ensures that communities are also central to discussions around and implementation of the design of the map. While the cartographic processes may differ from those of a professional cartographer, the term cartography and cartographer are used (rather than mapping or mapmaker) to indicate the close attention to design this technique facilitates. A collaborative cartographer commits to work that supports community control, embraces multiple forms of knowledge, and engages in non-linear and iterative process. These three key elements work together to support the production of a map whose standards of effectiveness are defined specifically by the needs, desires, and goals of those who produced it. This may lead to the creation of maps that fall outside of traditional expectations of cartographic design, aesthetic, and function. However, such creative ruptures are considered a necessary aspect in the pursuit of community empowerment and liberation.

GS-27 - GIS&T for Equity and Social Justice

A geographic information system (GIS) can be used effectively for activities, programs, and analyses focused on equity and social justice (ESJ).  Many types of inequities exist in society, but race and space are key predictors of inequity. A key concept of social justice is that any person born into society, no matter where they were born or live, will have an equitable opportunity to achieve successful life outcomes and to thrive. Geographic information science and its technologies (GIS&T) provide powerful tools to analyze equity and social justice issues and help government agencies apply an equity lens to every aspect of their administration. Given the reliance on spatial data to represent and analyze matters of ESJ, the use of these tools is necessary, logical, and appropriate. Some types of analyses and mapping commonly used with ESJ programs require careful attention to how data are combined and represented, risking misleading or false conclusions otherwise. Such outcomes could build mistrust when trust is most needed. A GIS-supported lifecycle for ESJ is presented that includes stages of exploratory issue analysis, community feedback, pro-equity programs analysis, management monitoring and stakeholder awareness, program performance metrics, and effectiveness analysis.