What is GIS?
GIS is a technology that is used to view and analyze data from a geographic perspective. The technology is a piece of an organization's overall information system framework.
GIS links location to information (such as people to addresses, buildings to parcels, or streets within a network) and layers that information to give you a better understanding of how it all interrelates. You choose what layers to combine based on your purpose
GIS manages, analyzes, and displays geographic knowledge, which is represented using a series of information sets. The information sets include:
Maps and GlobesInteractive views of geographic data with which to answer many questions, to present results, and to use as a dashboard for real work. Maps and globes provide advanced GIS applications for interacting with geographic data. |
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Geographic Data SetsFile bases and databases of geographic information—features, networks, topologies, terrains, surveys, and attributes. |
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Processing and Work Flow ModelsCollections of |
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Data ModelsGIS datasets are more than DBMS tables. They incorporate advanced behavior and integrity like other information systems. The schema, behavior, and integrity rules of geographic data sets play a critical role in GIS. |
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MetadataDocuments describing the other elements. A document catalog enables users to organize, discover, and gain access to shared geographic knowledge. |
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Source: GIS.com |
Three Views of a GIS
A GIS is most often associated with maps. A map, however, is only one of three ways a GIS can be used to work with geographic information. These three ways are:
- The Database View: A GIS is a unique kind of database of the world—a geographic database ( geodatabase). It is an "Information System for Geography." Fundamentally, a GIS is based on a structured database that describes the world in geographic terms.
- The Map View: A GIS is a set of intelligent maps and other views that show features and feature relationships on the earth's surface. Maps of the underlying geographic information can be constructed and used as "windows into the database" to support queries, analysis, and editing of the information. This is called geovisualization.
- The Model View: A GIS is a set of information transformation tools that derive new geographic datasets from existing datasets. These geoprocessing functions take information from existing datasets, apply analytic functions, and write results into new derived datasets.
Source: GIS.com |
Why Use GIS?
GIS is much more than mapping software. Maps are only one of three views of a GIS . When deployed with a clear strategy, GIS is a technology that can change an organization fundamentally and positively.
Modeling Our World
Most computer technology is designed to increase a decision-maker's access to relevant data. GIS goes beyond mining data to give you the tools to interpret that data, allowing you to see relationships, patterns, or trends intuitively that are not possible to see with traditional charts, graphs, and spreadsheets.
More than that, a GIS lets you model scenarios to test various hypotheses and see outcomes visually to find the outcome that meets the needs of all the stakeholders. For example, a retail manager looking to build a new store can analyze consumer demographics and the locations of competitors in relation to potential locations in a spreadsheet view. GIS lets that manager visualize potential locations on a map along with drive-time analysis, environmental concerns such as wetlands or protected species that might hamper construction, or any number of siting criteria that would be too cumbersome to comprehend otherwise.
Source: GIS.com |
What can you do with GIS?
Map Where Things Are
Mapping where things are lets you find places that have the features you're looking for, and to see where to take action.
- Find a feature—People use maps to see where or what an individual feature is.
- Finding patterns—Looking at the distribution of features on the map instead of just an individual feature, you can see patterns emerge.
Map Quantities
People map quantities, like where the most and least are, to find places that meet their criteria and take action, or to see the relationships between places. This gives an additional level of information beyond simply mapping the locations of features.
For example, a catalog company selling children's clothes would want to find ZIP Codes not only around their store, but those ZIP Codes with many young families with relatively high income. Or, public health officials might not only want to map physicians, but also map the numbers of physicians per 1,000 people in each census tract to see which areas are adequately served, and which are not.
Map Densities
While you can see concentrations by simply mapping the locations of features, in areas with many features it may be difficult to see which areas have a higher concentration than others. A density map lets you measure the number of features using a uniform area unit, such as acres or square miles, so you can clearly see the distribution.
Mapping density is especially useful when mapping areas, such as census tracts or counties, which vary greatly in size. On maps showing the number of people per census tract, the larger tracts might have more people than smaller ones. But some smaller tracts might have more people per square mile—a higher density.
Find What's Inside
Use GIS to monitor what's happening and to take specific action by mapping what's inside a specific area. For example, a district attorney would monitor drug-related arrests to find out if an arrest is within 1,000 feet of a school--if so, stiffer penalties apply.
Find What's Nearby
Find out what's occurring within a set distance of a feature by mapping what's nearby.
Map Change
Map the change in an area to anticipate future conditions, decide on a course of action, or to evaluate the results of an action or policy.
- By mapping where and how things move over a period of time, you can gain insight into how they behave. For example, a meteorologist might study the paths of hurricanes to predict where and when they might occur in the future.
- Map change to anticipate future needs. For example, a police chief might study how crime patterns change from month to month to help decide where officers should be assigned.
- Map conditions before and after an action or event to see the impact. A retail analyst might map the change in store sales before and after a regional ad campaign to see where the ads were most effective.
Source: GIS.com |
What is GPS?
GPS (Global Positioning System) is a network of satellites that continuously transmit coded information, which makes it possible to precisely identify locations on earth by measuring distances from the satellites.
GPS refers to a group of U.S. Department of Defense satellites constantly circling the earth. The satellites transmit very low power radio signals allowing anyone with a GPS receiver to determine their location on Earth.
Sources of Error
Ionosphere and troposphere delays - The satellite signal slows as it passes through the atmosphere. The system uses a built-in "model" that calculates an average, but not an exact, amount of delay. |
Signal Multi-path - Occurs when the GPS signal is reflected off objects such as tall buildings or large rock surfaces before it reaches the receiver. This increases the travel time of the signal, thereby causing errors. |
Receiver clock errors - Since it is not practical to have an atomic clock in your GPS receiver, the built -in clock can have very slight timing errors. |
Orbital errors - Also known as "ephemeris errors", these are inaccuracies of the satellite's reported location. |
Number of Satellites visible - The more satellites the receiver can "see", the better the accuracy. Buildings, terrain, electronic interference, or sometimes even dense foliage can block signal reception, causing position errors or possibly no position reading at all. The clearer the view, the better the reception. |
Satellite geometry/shading - This refers to the relative position of the satellites at any given time. Ideal satellite geometry exists when the satellites are located at wide angles relative to each other. Poor geometry results when the satellites are located in a line or in a tight grouping. |
"How To" Documents
The "Deployment" phase covers systems installation, application functional testing, performance testing and user training. None of these, except for user training apply to the I-GIS at the moment. The support section provides various user training options including "how to" documents and frequently asked questions.
"How To" Open a Project Template
"How To" Edit metadata
"How To" Use the GPS Receiver