“After more than 30 years, we are still confronted by the same major challenge that GIS professionals have always faced: You must have good data. And good data are expensive and difficult to create.” (Wilson, 2001, p. 54)

Data consist of symbols that represent measurements of phenomena. People create and study data to help understand how natural and social systems work. Such systems can be hard to learn because they are made up of many interacting phenomena that are often difficult to observe directly and tend to change over time. We attempt to make systems and phenomena easier to study by measuring their characteristics at certain times. Because it is not practical to measure everything, everywhere, at all times, we measure selectively. How accurately data reflect the phenomena they represent depends on how, when, where, and what aspects of the phenomena were measured. All measurements, however, contain a certain amount of error.

Measurements of the locations and characteristics of phenomena can be represented with several distinct kinds of symbols. For example, pictures of the land surface, including photographs and maps, are made up of graphic symbols. Verbal descriptions of property boundaries are recorded on deeds using alphanumeric symbols. Locations determined by satellite positioning systems are reported as pairs of numbers called coordinates. All data types – images, words, and numbers – can be digitally represented on computers. Obviously, digital data can be stored, transmitted, and processed much more efficiently than their physical counterparts that are printed on paper. These advantages set the stage for the development and widespread adoption of GIS.

Information is data selected or created in response to a question. For example, the location of a building or a route is data until they are needed to dispatch an ambulance in response to an emergency. When used to inform those who need to know “where is the emergency, and what is the fastest route between here and there?” the data are transformed into information. Data transformation involves the ability to ask the right kind of question and the ability to retrieve existing data or to generate new data from the old that helps people answer the question. The more complex the question and the more locations involved, the harder it becomes to produce timely information with paper maps alone.

Interestingly, the potential value of data is not necessarily lost when used. On the contrary, data can be transformed into information repeatedly, provided that the data are kept up-to-date. Given the rapidly increasing accessibility of computers and communications networks in the U.S. and abroad, it is not surprising that information has become a commodity and that the ability to produce it has become a significant growth industry.

Information Systems

Information systems are computer-based tools that help people transform data into information. Many problems and opportunities faced by government agencies, businesses, and other organizations are complex. In addition, they involve so many locations that the organizations need assistance creating valuable and timely information. That is what information systems are for.

To understand how we get from analog to digital maps, let us begin with the building blocks and foundations of the geographic information system (GIS) – namely, data and information. Geographic information systems store, edit, process, and present data and information. However, what exactly is data? Moreover, what exactly is information? The terms “data” and “information” refer to the same thing for many. For our purposes, it is helpful to distinguish between the two. Data refer to facts, measurements, characteristics, or traits of an object of interest. For example, we can collect data about geographic features, like the length of rainbow trout in a Colorado stream, the diameter of mahogany tree trunks in the Brazilian rainforest, student scores on the last GIS midterm, or the altitude of mountain peaks in Nepal.

Once data are put into context, used to answer questions, situated within analytical frameworks, or obtained insights, they become information. Information refers to the knowledge of value obtained through collecting, interpreting, and analyzing data. Though a computer is not necessary to collect, record, manipulate, process, or visualize data or process it into information, information technology can significantly help. For instance, computers can automate repetitive tasks, store data efficiently in terms of space and cost, and provide tools for analyzing data from spreadsheets to GIS. In addition, an incredible amount of data is collected daily by satellites, grocery store product scanners, traffic sensors, temperature gauges, smartphone apps, and endlessly more. Again, this data would not be possible without the aid and innovation of information technology.

Geographic or spatial data refer to an object’s geographic facts, measurements, or characteristics that permit us to define its location on the earth’s surface. Such data include, but are not restricted to, the latitude and longitude coordinates of points of interest, street addresses, postal codes, political boundaries, and even the names of places of interest. It is also important to note and reemphasize geographic and attribute data differences. Geographic data defines the location of an object of interest; attribute data is concerned with its nongeographic traits and characteristics.

“Spatial data is information about the locations and shapes of geographic features and the relationship between them, usually stored as coordinates and topology.” – Esri

To illustrate the distinction between geographic and attribute data, think about your home, where you grew up, or where you currently live. Within the context of this discussion, we can associate geographic and attribute data to it. We can define the location of your home in many ways, such as with a street address, the street names of the nearest intersection, the zip code or Census block your home is located in, or latitude and longitude coordinates. What is essential is that geographic data permit us to define the location of an object on the surface of the earth.

In addition to the geographic data that defines the location of your home are the attribute data that describes the various qualities of your home. Such data could include the number of bedrooms and bathrooms in your home, whether your home has central air, the year your home was built, the number of occupants, or whether there is a swimming pool. These attribute data tell us much about your home but little about where it is.

It is beneficial to recognize and understand how geographic and attribute data differ and complement each other, but it is also vital when learning about and using GIS. Because a GIS requires and integrates these two distinct types of data, being able to differentiate between geographic and attribute data is the first step in organizing your GIS. Furthermore, determining which data you need will aid in implementing and using a GIS. Often, and in the age and context of information technology, the data and information discussed thus far is the stuff of computer files, which are the focus of the next section.

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