3.1 Types of Maps
The primary output of a GIS is a map. For a GIS to be widely useful, maps must be created to disseminate the data. That’s not to say that maps are the only output of a GIS, as statistics, reports, and videos, among others, can be outputs from a GIS, however, maps are the primary means in which spatial information is displayed from a GIS.
Let us first define the idea of a map. A map is a graphic representation of a milieu. What that means is a map is a way of representing our world-based on the knowledge and culture of the mapping society at a particular time in history. The purpose of a map is to transmit knowledge visually, and is often considered to be one of the three major modes of communication.
A cartographer is someone who designs and prepares a map for distribution. Cartographers also study the philosophical and theoretical bases of the rules for making maps. Cartographers are trained professionals in the field of cartography which is the art and science of making maps. Cartography is a professional field that has existed for hundreds of years, and it takes cartographers many years of apprenticeship to become skilled at their craft. However, nowadays, with computer technology allowing us to quickly manipulate, analyze, and visualize spatial information, map-making is now being shared by professions outside of cartography. Therefore, it is important that any user of a GIS, be trained in cartography so that their maps will be effective communications. This module will provide an introductory look at the skills required to perform proper cartographic design for maps.
Broadly speaking, there are two kinds of maps: reference maps, and thematic maps. The reference map emphasizes the location of objects in the world. It also shows a variety of the world, and primarily displays physical objects. A thematic map, on the other hand, emphasizes attributes. Typically, a thematic map will display information pertaining to a single subject, or theme, and will emphasize the spatial patterns, and variations of an attribute in that theme.
If we drill down into the thematic map kind, there are two types of thematic maps: qualitative, and quantitative. A qualitative map shows nominal data and focuses on the distribution of that nominal information. It is important to note, that since it is a qualitative map, it is not focused on the variation of quantities, rather, it focuses on the location of distribution of kinds of things. The quantitative map, on the other hand, shows numerical data, and focuses on the variation of that numerical information from place to place. It is common practice to generalize numbers on a quantitative thematic map, so that the information being visualized can display potentially hidden patterns, and appropriate scales.
Let’s take a look at an example of a qualitative thematic map. This thematic map is a qualitative thematic map showing the standard Time zones of the United States of America taken from the national Atlas. Since a time zone is a nominal type of information, this map focuses on the distribution and location of the time zones, but not any numerical, or quantitative information. In other words, it only shows the different kinds of time zones and where they’re located.
Now let’s consider a quantitative thematic map showing a single variable. This quantitative thematic map shows the relative advantage of votes gained by each of the two major party candidates in the 2008 presidential election in the United States of America. The voting information has been aggregated to County level information, for two reasons: one, so that the data can be clearly seen at this map scale, and two, so that patterns of distribution of the quantitative voting information can be more easily seen.
In addition to the kinds of maps, there are three mediums on which a map may be produced for distribution: tangible, virtual, and mental. A tangible map medium is any concrete object that can be manifested physically, and passed from person to person. For maps, the most common tangible medium is paper. Paper has many advantages as a medium, such as ease of transport, low cost of production, and no requirement of specialized hardware or software to view. A disadvantage of paper maps is that they are not easily updatable, cannot show dynamic content, and are set at a single scale. The virtual map medium is when the map is stored in a computer’s memory and visualized on output device, such as a monitor, or tablet screen. The virtual medium has the advantage of being easily updatable, supporting animation, able to switch between scales, and able to quickly transport large distances. Disadvantages are that it requires an investment of hardware and software to view, and may not be as intuitive to use as a tangible map. The third medium is the mental medium of maps. A mental map is a map that is stored inside your mind. This mental map is your conceptualization of reality. Mental maps are not concrete, nor are they stored inside of a computer. Therefore, mental maps cannot be transferred between people, without first becoming either tangible, or virtual. In the field of GIS, tangible and virtual maps are the two most common mediums of maps.
In summary, we can create a tree to show how the concepts of map types, map kinds, and map mediums work together. Starting at the top, a map type is stored as either a mental, tangible, or virtual medium. If the map is stored on a tangible or virtual medium, then this will be either a reference, or thematic map. Thematic maps can be further broken down into qualitative or quantitative maps. A quantitative map can display a single or multiple variables at once.
Let us first define the idea of a map. A map is a graphic representation of a milieu. What that means is a map is a way of representing our world-based on the knowledge and culture of the mapping society at a particular time in history. The purpose of a map is to transmit knowledge visually, and is often considered to be one of the three major modes of communication.
A cartographer is someone who designs and prepares a map for distribution. Cartographers also study the philosophical and theoretical bases of the rules for making maps. Cartographers are trained professionals in the field of cartography which is the art and science of making maps. Cartography is a professional field that has existed for hundreds of years, and it takes cartographers many years of apprenticeship to become skilled at their craft. However, nowadays, with computer technology allowing us to quickly manipulate, analyze, and visualize spatial information, map-making is now being shared by professions outside of cartography. Therefore, it is important that any user of a GIS, be trained in cartography so that their maps will be effective communications. This module will provide an introductory look at the skills required to perform proper cartographic design for maps.
Broadly speaking, there are two kinds of maps: reference maps, and thematic maps. The reference map emphasizes the location of objects in the world. It also shows a variety of the world, and primarily displays physical objects. A thematic map, on the other hand, emphasizes attributes. Typically, a thematic map will display information pertaining to a single subject, or theme, and will emphasize the spatial patterns, and variations of an attribute in that theme.
If we drill down into the thematic map kind, there are two types of thematic maps: qualitative, and quantitative. A qualitative map shows nominal data and focuses on the distribution of that nominal information. It is important to note, that since it is a qualitative map, it is not focused on the variation of quantities, rather, it focuses on the location of distribution of kinds of things. The quantitative map, on the other hand, shows numerical data, and focuses on the variation of that numerical information from place to place. It is common practice to generalize numbers on a quantitative thematic map, so that the information being visualized can display potentially hidden patterns, and appropriate scales.
Let’s take a look at an example of a qualitative thematic map. This thematic map is a qualitative thematic map showing the standard Time zones of the United States of America taken from the national Atlas. Since a time zone is a nominal type of information, this map focuses on the distribution and location of the time zones, but not any numerical, or quantitative information. In other words, it only shows the different kinds of time zones and where they’re located.
Now let’s consider a quantitative thematic map showing a single variable. This quantitative thematic map shows the relative advantage of votes gained by each of the two major party candidates in the 2008 presidential election in the United States of America. The voting information has been aggregated to County level information, for two reasons: one, so that the data can be clearly seen at this map scale, and two, so that patterns of distribution of the quantitative voting information can be more easily seen.
In addition to the kinds of maps, there are three mediums on which a map may be produced for distribution: tangible, virtual, and mental. A tangible map medium is any concrete object that can be manifested physically, and passed from person to person. For maps, the most common tangible medium is paper. Paper has many advantages as a medium, such as ease of transport, low cost of production, and no requirement of specialized hardware or software to view. A disadvantage of paper maps is that they are not easily updatable, cannot show dynamic content, and are set at a single scale. The virtual map medium is when the map is stored in a computer’s memory and visualized on output device, such as a monitor, or tablet screen. The virtual medium has the advantage of being easily updatable, supporting animation, able to switch between scales, and able to quickly transport large distances. Disadvantages are that it requires an investment of hardware and software to view, and may not be as intuitive to use as a tangible map. The third medium is the mental medium of maps. A mental map is a map that is stored inside your mind. This mental map is your conceptualization of reality. Mental maps are not concrete, nor are they stored inside of a computer. Therefore, mental maps cannot be transferred between people, without first becoming either tangible, or virtual. In the field of GIS, tangible and virtual maps are the two most common mediums of maps.
In summary, we can create a tree to show how the concepts of map types, map kinds, and map mediums work together. Starting at the top, a map type is stored as either a mental, tangible, or virtual medium. If the map is stored on a tangible or virtual medium, then this will be either a reference, or thematic map. Thematic maps can be further broken down into qualitative or quantitative maps. A quantitative map can display a single or multiple variables at once.