An example of this kind of information is computer data collected by satellites that show land use-the location of farms, towns, and forests. Photo interpretation involves analyzing aerial photographs and assessing the features that appear.ĭigital data can also be entered into GIS. Photographic interpretation is a major part of GIS. Cartographic data may also include survey data and mapping information that can be directly entered into a GIS. These applications may include cartographic data, photographic data, digital data, or data in spreadsheets.Ĭartographic data are already in map form, and may include such information as the location of rivers, roads, hills, and valleys. GIS applications include both hardware and software systems. Such a map would help people determine where water supplies are most at risk. 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. With GIS technology, people can compare the locations of different things in order to discover how they relate to each other. It can include information about the sites of factories, farms, and schools, or storm drains, roads, and electric power lines. It can include information about the landscape, such as the location of streams, different kinds of vegetation, and different kinds of soil. The system can include data about people, such as population, income, or education level. Many different types of information can be compared and contrasted using GIS. The location can be expressed in many different ways, such as latitude and longitude, address, or ZIP code. GIS can use any information that includes location. GIS technology is a crucial part of spatial data infrastructure, which the White House defines as “the technology, policies, standards, human resources, and related activities necessary to acquire, process, distribute, use, maintain, and preserve spatial data.” By relating seemingly unrelated data, GIS can help individuals and organizations better understand spatial patterns and relationships. It is now simple to see how the messages relate to one another.A geographic information system (GIS) is a computer system for capturing, storing, checking, and displaying data related to positions on Earth’s surface. In order for the journe圜alculation to be able to respond, it sends two messages out, 3.1 getCurrentLocation() to the GPS location object and another one 3.2 getDestinationLocation() to the Destination details object. You can use a decimal system to denote various levels.įor example, the third message from the display screen is ' 3 getJourneyData()' this goes to the Journe圜alculations object. This is done by prefixing the messages with a sequence number. If it is not obvious what the return type should be then that should also be included.Īnother feature of the communication diagram is the ability to track the ultimate source of a message. If the message needs to include a parameter, then that should be included as well. The arrows indicate a message being sent, for example the Mapping object sends a message to the GPS location object asking about the car's current location. The example below shows a notional car navigation system. Communication diagrams are used to show the messages that flow from one object to another within the system and the order in which they happen.Ī communication diagram is fairly similar to an object diagram in that it uses the same graphics for objects, the same line styles to denote inheritance and association.īut in addition, a list of the messaging methods are drawn.
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