UNIT 1: PHYSICAL GEOGRAPHY

The digital mapping revolution caused an explosion of map creation in the 1990s. In 1996, MapQuest, the first popular online mapping service, allowed anyone with internet access the ability to create customized maps of almost any location in the United States. Within a few months, millions of people had become “cartographers”. They were soon producing more unique maps in a single day than had been created during the entire history of paper cartography!

GPS

For thousands of years, we have used the position of the stars to navigate. Now, using artificial "stars" (satellites), we can navigate using computers and the Global Positioning System. The GPS system is based on a network of satellites that send out signals along the radio frequency. This system provides accurate positions no matter the weather, time of day or location. As long as a GPS unit can get a proper signal, the position can be determined. These satellites orbit the earth twice a day at very high altitude. A user with a GPS receiver needs at least four satellites above the horizon in order to able to computer his position. Each of these satellites will tell the receiver how far the satellite is away and the satellite's exact position in space. The GPS receiver now does some fancy math to figure out absolute position, usually in latitude and longitude. GPS receivers can theoretically be accurate down to centimeters, but usually they are not this accurate due to various errors.

Once just used for science, GPS units have become affordable enough that they are used by emergency services, utilities and your average car driver. Geographers use GPS to accurately record the position of an area of interest and in remote sensing.

GIS

A geographic information system (GIS) is a computer system for capturing, storing, checking, and displaying data related to positions on Earth’s surface. By relating seemingly unrelated data, GIS can help individuals and organizations better understand spatial patterns and relationships.
 
GIS technology is a crucial part of spatial data infrastructure, which may be defined as “the technology, policies, standards, human resources, and related activities necessary to acquire, process, distribute, use, maintain, and preserve spatial data.”

GIS can use any information that includes location. The location can be expressed in many different ways, such as latitude and longitude, address, or postal code.
 
Many different types of information can be compared and contrasted using GIS. The system can include data about people, such as population, income, or education level. It can include information about the landscape, such as the location of streams, different kinds of vegetation, and different kinds of soil. It can include information about the sites of factories, farms, and schools; or storm drains, roads, and electric power lines.
 
With GIS technology, people can compare the locations of different things in order to discover how they relate to each other. For example, using GIS, a single map could include sites that produce pollution, such as factories, and sites that are sensitive to pollution, such as wetlands and rivers. Such a map would help people determine where water supplies are most at risk.

Data Capture

Putting information into GIS is called data capture. Data that are already in digital form, such as most tables and images taken by satellites, can simply be uploaded into GIS. Maps, however, must first be scanned, or converted to digital format.
 
GIS applications include both hardware and software systems. These applications may include cartographic data, photographic data, digital data, or data in spreadsheets. Cartographic data are already in map form, and may include such information as the location of rivers, roads, hills, and valleys. Cartographic data may also include survey data, mapping information which can be directly entered into a GIS. Additionally, photographic interpretation is a major part of GIS. Photo interpretation involves analyzing aerial photographs and assessing the features that appear. Digital data can also be entered into GIS. An example of this kind of information is computer data collected by satellites that show land use—the location of farms, towns, and forests.
 
Finally, GIS can also include data in table or spreadsheet form, such as population demographics. Demographics can range from age, income, and ethnicity to recent purchases and Internet browsing preferences. GIS technology allows all these different types of information, no matter their source or original format, to be overlaid on top of one another on a single map. GIS uses location as the key index variable to relate these seemingly unrelated data.

 
Spatial Relationships
GIS technology can be used to display spatial relationships and linear networks. Spatial relationships may display topography, such as agricultural fields and streams. They may also display land-use patterns, such as the location of parks and housing complexes.
 
Linear networks, sometimes called geometric networks, are often represented by roads, rivers, and public utility grids in a GIS. A line on a map may indicate a road or highway. With GIS layers, however, that road may indicate the boundary of a school district, public park, or other demographic or land-use area. Using diverse data capture, the linear network of a river may be mapped on a GIS to indicate the stream flow of different tributaries. GIS must make the information from all the various maps and sources align, so they fit together on the same scale. A scale is the relationship between the distance on a map and the actual distance on Earth.
 
Often, GIS must manipulate data because different maps have different projections. A projection is the method of transferring information from Earth’s curved surface to a flat piece of paper or computer screen. Different types of projections accomplish this task in different ways, but all result in some distortion. To transfer a curved, three-dimensional shape onto a flat surface inevitably requires stretching some parts and squeezing others. A world map can show either the correct sizes of countries or their correct shapes, but it can’t do both. GIS takes data from maps that were made using different projections and combines them so all the information can be displayed using one common projection.

Once all of the desired data have been entered into a GIS system, they can be combined to produce a wide variety of individual maps, depending on which data layers are included. One of the most common uses of GIS technology involves comparing natural features with human activity. Below is a GIS map of Hamilton, Ontario that has been used to visualize crime hot-spots such as burglaries.

GIS maps can display what manmade features are near certain natural features, such as which homes and businesses are in areas prone to flooding. It also allows to “dig deep” in a specific area with many kinds of information. Maps of a single city or neighborhood can relate such information as average income, book sales, or voting patterns. Any GIS data layer can be added or subtracted to the same map. As well, GIS maps can be used to show information about numbers and density. For example, GIS can show how many doctors there are in a neighborhood compared with the area’s population.  With GIS technology, researchers can also look at change over time. They can use satellite data to study topics such as the advance and retreat of ice cover in polar regions, and how that coverage has changed through time. A police precinct might study changes in crime data to help determine where to assign officers.
 
One important use of time-based GIS technology involves creating time-lapse photography that shows processes occurring over large areas and long periods of time. For example, data showing the movement of fluid in ocean or air currents help scientists better understand how moisture and heat energy move around the globe. GIS technology sometimes allows users to access further information about specific areas on a map. A person can point to a spot on a digital map to find other information stored in the GIS about that location. For example, a user might click on a school to find how many students are enrolled, how many students there are per teacher, or what sports facilities the school has. GIS systems are often used to produce three-dimensional images. This is useful, for example, to geologists studying earthquake faults.
 
GIS technology makes updating maps much easier than updating maps created manually. Updated data can simply be added to the existing GIS program. A new map can then be printed or displayed on screen. This skips the traditional process of drawing a map, which can be time-consuming and expensive.