Editor's note: The terms geospatial and geographic are used interchangeably in this article.
Since man first appeared, there has been an interest in maps. The walls of caves in Lascaux, France were decorated by Cro-Magnon hunters with images of animals they hunted. Alongside the images are track lines and other graphical notation associated with the grounds where the animals were. In a crude way, these maps represent the earliest two-dimensional (2D) form of a geospatial information system (GIS).
We've come a long way since the Cro-Magnon times. Today's computerized GISs consist of spatial (or geographically referenced) data and software to:
- Analyze, visualize, manage, and disseminate the spatial data.
- Automate workflow activities.
Examples of geographically referenced data include information about rivers, lakes, continents, countries, cities, and residences.
Vector and raster data are the two common and extensively used GIS data formats in GISs.
- Vector data
- Is useful in representing features that have boundaries, such as
landmarks, highways, countries, lakes, and watersheds. Features are
represented using three basic shapes: points, lines, and polygons.
Figure 1 shows an example of vector data.
Features have a geographic location and are stored as coordinates.
Latitude and longitude, or another system of measurement, are used to
locate features. Location coordinates also define the feature shape. A
single coordinate defines a point. Two coordinates define a line, and
three or more coordinates define a polygon.
For example, a business or landmark can be displayed as a point on a map (single coordinate). A street can be displayed as a line (two coordinates), a highway can be displayed as a series of lines, and a country, lake, or watershed can be displayed as a polygon on a map (three or more coordinates).
Features have four properties: shape, location, symbol, and attributes. The city of New York, for example, is a feature on a world map. Because it's on a map that represents such a large surface area, New York City is represented by a simple point shape, such as a star, and is located at specific latitude and longitude coordinates. New York may be further denoted on the world map by attributes such as name and population.
A layer is a collection of similar features. Features in a layer represent the same type of things, such as roads, lakes, countries, watersheds, and so on. Features in a layer have the same shape and same set of attributes. In Figure 1, customers and streets are examples of layers.
- Raster data
- Is useful to represent continuous data that has no well-defined shapes or boundaries. Vegetation and terrain are just two examples of raster data. Raster format uses cells arranged in rows and columns to store data. Every cell stores a value. Every raster has an origin, which defines a real-world location. Each cell in the raster has a unique position relative to the origin. Using the attributes of the cell, such as position, size, and coordinates of the origin, a GIS can calculate the real-world location of every cell in a raster. Figure 1 shows an example of raster data.
Figure 1. Vector and raster data (Source: ESRI)
GIS data is usually created in one of two primary coordinate systems: geographic and projected. Geographic coordinate systems are based on the Earth's surface, or its curvature. Geographic is a three-dimensional (3D) coordinate system; the unit of measure is degrees, which have values for latitude and longitude.
Projected coordinate systems are 2D planar coordinate systems used to create maps. Projected coordinate systems convert geographic coordinates to a 2D plane. The units of measure for projected systems are typically either meters or feet.
Data from different GISs will occasionally require conversion to a common coordinate system (either projected or geographic). For example, New York state geographical data may be available only in a geographic coordinate system, while data for New Jersey is in a projected coordinate system. In this case, a conversion to a common format will be required before the merged data can be useful.
The five properties of a GIS are:
- Visualization
- Spatial analysis
- Data management
- Workflow management
- Dissemination of information
- Visualization
- Pictures of data are usually displayed on a map. Facilities, such as simple operations like zooming, are provided to the end user. More complex functions are also possible, including 3D visualization, modifying data using paintbrush techniques, and visualizing the effects in real time.
- Spatial analysis
- Because spatial data is stored in defined data tables, you can run
queries against the data for analysis and decision making. For example,
location and attribute are two types of queries you
can run against GIS data.
You can use attribute query to find features that have certain values. For example:
- Which highways in New York have tolls?
- What are the names of the lakes in the state of New York?
Location query is used to find features with locations that meet certain conditions usually related to other features. For example:
- Which states in the U.S. does Interstate 80 go through?
- How many lakes are there in the state of New York?
- How many states are adjacent to the state of New York?
- How many cities are within 500 miles of New York city?
- Data management
- GISs use well-defined processes on how data is stored, accessed, and managed. These processes include maintaining integrity of spatial data, multiuser access with versioning capabilities, and integrating spatial data with nonspatial data to make it useful to users.
- Workflow
- Most GISs contain some sort of sequence of operations involving different users or components of the system. For example, a water management company might obtain the locations of new fire hydrants from a city government. The water management company then formats this data for their GIS. It then augments the data with information specific to its products or methodologies (age of hydrant, last serviced, and so on). This same location information might also be provided to the city fire department, or other civil works departments, to be used in decision-making processes of the organization.
- Dissemination of information
- GIS data is typically disseminated to Web-based user interfaces, desktop software, or handheld devices, depending on the needs of the end user. Web services are also provided to accommodate SOA-based architectures.
Geospatial information systems are useful for businesses, educational institutions, government entities, nonprofit organizations, and the general public. All have different priorities, but each can use GIS every day to solve real-world problems. Whether the priority is to generate profits, plan budgets, plan product distribution, manage resources, increase efficiency, or decrease costs, GIS provides the tools to help get the job done. This section includes just a few of the numerous examples.
Many transportation companies use GISs to create better product distribution patterns. They use GISs that contain maps of delivery areas. The maps include delivery points and local ordinances (noise and livery time restrictions, speed limits, and so on). Data about traffic conditions may also be available, along with number of available delivery vehicles, delivery capacity per vehicle, and the volume of deliveries. Using this data, transportation companies can easily calculate the best delivery routes.
Publicly available applications such as MapQuest quickly provide nontechnical users with a wealth of helpful geographic and travel information. Detailed driving directions are available with minimal data entry. With just another click or two, the user can also get local traffic and road conditions and optional information such as location of hotels, restaurants, and gas stations along the travel route.
Google Maps provides interactive maps and driving directions. Google Maps also integrates aerial or satellite imagery of many countries and keyword search capability to easily locate businesses and other landmarks (residences, historic sites, libraries, schools, and so forth).
Google Earth and Microsoft® Visual Earth are both geographical browsers that access satellite or aerial images of varying resolution, providing the user with a bird's-eye view of buildings, traffic, weather, and places of interest.
Before launching a new customer service center, utility companies are increasingly using GISs to analyze their customer demographics and distribution to plan for the most efficient location. An optimal location reduces total drive time for service calls or meter reads, which in turn saves money and leads to increased efficiency and customer satisfaction.
Similarly, during business expansion planning, utility companies might use a GIS to identify environmentally protected areas. Or they could use GIS to determine the proximity to the nearest sources of water, and the data would help with calculating the investment needed to bring water to a new plant.
A top priority for many local governments is good urban growth planning. GIS data, such as land use and zoning, is helpful to planning departments as they identify and target areas for growth.
Budget planning for housing and health services is also critical to governments. Many city governments use local geographic boundaries and population demographic data (incomes, poverty levels, age, mortality rates, number of physicians) to determine areas where public housing and public health services are most needed.
Fire and emergency services departments in large cities use GISs to identify the location of fire hydrants and waterways. When a fire or other emergency occurs, this information is coordinated with road maps and the location of the fire to provide critical information about the number of firefighters and emergency service vehicles required.
During impending natural disasters, such as hurricanes and floods, government agencies likewise use GISs to plan for emergency relief of the affected areas, including population information and location of hospitals.
Conservation agencies use geographical data and scientific models to understand common trade-offs that occur in river basin management. Agricultural production, water availability, water quality, biodiversity, carbon storage, and hydropower generation are considerations for certain areas.
When launching new projects, real estate development companies use GIS to identify the best possible location to maximize profits. The development companies use local geographic information and similar existing data, such as business locations, population demographics, traffic, and roads.
Open source as opposed to proprietary software
The architecture in Figure 2 gives you an idea of the different software components that comprise a basic GIS architecture. Enterprise GISs usually contain an integration component, which is not shown in the architecture below. GISs can be built using open source software, proprietary (license required) software, or a combination of the two.
Open source GIS software is rapidly improving and, in most cases, can provide a robust alternative to proprietary software. In the open source arena, there are many choices; among the most popular are University of Minnesota's MapServer to serve maps, OpenLayers to build Web-based user interfaces, and the PostGRES / PostGIS combination for databases with GIS capabilities.
Environmental Systems Research Institute (ESRI) is the leading software vendor for GIS. ESRI provides many different software products: desktop software to manage and visualize GIS data, toolkits, and application development frameworks to build Web-based user interfaces. ESRI's arcGIS server provides powerful mapping, visualization, and data management capabilities to do complex tasks. arcGIS server works very well with leading database products such as DB2, Oracle, and Sqlserver. arcGIS server version 9.3 also supports PostGres/PostGIS open source database.
Figure 2. High-level GIS architecture
The architecture consists of four major components:
- User interface
- Web browsers: Increasingly popular choice for interaction with the GIS.
- Desktop software: Used for complex spatial data manipulation and visualization tasks with direct connection to the GIS server.
- Mobile devices: Support one-way and two-way data replication tasks.
- Web application server
- HTTP server: The Web server that processes the HTTP requests.
- Application server: Contains the Web application and supports client-side APIs (such as JavaScript) and server side logic (such as servlets, Enterprise JavaBeans (EJBs)) to invoke GIS server tasks.
- Database connection: Java Database Connectivity (JDBC) or Open Database Connectivity (ODBC) API to connect to the database.
- GIS Server
- Provides visualization, spatial data analysis, mapping, and spatial data management services.
- Supports complex workflow activities, including versioning.
- Database
- The database server to persist spatial and nonspatial data.
The architecture in Figure 2 is a standard 3-tier architecture, where user interface, middleware (Web application server and GIS server), and database components are modularized.
In this article you learned the basics of spatial data, properties of a GIS, and examples of real-world uses. This article also discussed open source and proprietary software that's available to build a GIS.
Stay tuned for Part 2, which will explore in depth the technical details of the architecture: how the Web application server, GIS server, and database are integrated in a services component architecture implementation.
Learn
- ESRI, the GIS software market leader,
provides
white
papers
on numerous topics.
- The IBM Redpaper
Infrastructure
Recommendations for an ESRI and IBM Geographic Information System
introduces GIS and ESRI and discusses the software and hardware components
that are available to create a GIS system that meets the needs of a wide
range of users.
-
"The
State of Open Source GIS"
(Refractions Research Inc., Sep 2007) covers an array of topics.
-
IBM Maximo Asset Management Essentials
provides industrial strength GIS data asset management capabilities,
enabling smaller organizations to organize, track, and manage asset and
work management processes with industry-leading technology.
- Learn more about the various IBM products
that can be used to build a GIS, including
IBM WebSphere,
IBM DB2,
and
IBM BladeCenter® servers.
- Browse the
technology bookstore
for books on these and other technical topics.
- See the Wikipedia entry for more information on the cave drawings
in Lascaux, France.
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Scott Crowther is a software engineer for the IBM Corporate Information Office. He has been involved in a wide range of J2EE applications and solutions, including sales force automation, customer relationship management, cost recovery, legacy application conversion, collaboration, and GIS Web applications. He is also involved in leadership development studies.
A software engineer at IBM since 2003, Abe Guerra has worked in the IT industry since 2001. He holds a BBA in management and an MS in computer science from Pace University. He's currently developing GIS Web applications. His interests include artificial intelligence in virtual worlds.
Dr. George Raber received a BS in geographic information systems from Brigham Young University in 1999, and an MS and PhD in geography in 2001 and 2003 from the University of South Carolina. He began his current appointment in 2004. His research interests are primarily focused on land cover analysis and terrain modeling using remote sensing and spatial modeling in GIS.
Angel E. Tomala-Reyes is a software engineer for the IBM Corporate Information Office. Before joining IBM's CIO development team, he worked for IBM Global Services building distributed ticketing systems and other complex J2EE applications and integration solutions. He is focused on designing and implementing front-end applications using some of the latest technologies in the Web space. His mission is to create highly effective and highly adaptable user interfaces and to advance IBM's enterprise products.
Murali Vridhachalam is an Open Group certified IT architect and has been with IBM since 1994. He has architected and deployed several enterprise applications within IBM. His current interests include architecting solutions in the software as a service domain. He provides technical leadership to a team whose mission is to develop innovative solutions using IBM's wide array of enterprise software products.
