What is GIS?

Caitlin Dempsey


As an emerging technology , the field of geographic information systems (GIS) is constantly evolving.  Over a span of thirty years, members of the geographic information community have seen this technology evolve from command line, workstation-based software to complex geospatial tools that can now be used via web browsers and via mobile devices.

What is the Definition of a GIS?

What is GIS? This is probably the most asked question posed to those in the Geographic Information Systems (GIS) field and is probably the hardest to answer in a succinct and clear manner.

GIS is a technological field that incorporates geographical features with tabular data (otherwise known as attribute data) in order to map, analyze, and assess real-world problems.

The key word to this technology is Geography – this means that some portion of the data is spatial or geographical in nature.  GIS data is in some way referenced to locations on the earth. Coupled with this geospatial data is tabular data known as attribute data. 

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GIS data formats are created from a variety of historic and real-time sources such as field GIS data collection, GPS, LiDAR, satellite imagery, aerial photographs, and remote sensing. GIS data is used to analyze geographic phenomena, as basemaps, and to produce visualizations in the form of maps through the use of GIS software such as ArcGIS, QGIS, or GRASS GIS.

Data showing the boundaries and attribute information about properties in a given area.
Parcel data is a form of cadastral GIS Data showing the boundaries and attribute information about properties in a given area. Map: Caitlin Dempsey.

What is GIS Attribute Data?

Attribute data can be generally defined as additional information about each of the spatial features.  An example of this would be schools. The actual location of the schools is the spatial data.  Additional data such as the school name, level of education taught, student capacity would make up the attribute data. 

It is the partnership of these two data types that enables GIS to be such an effective problem solving tool through spatial analysis.

What is GIS Used For?

GIS operates on many levels.  On the most basic level, geographic information systems technology is used as computer cartography, that is for straight forward map making.

There are numerous ways in which GIS is used across different industries.  A few examples are:

  1. Emergency response teams normally use GIS when they want to collect logistics with regards to how they will move in times of natural disasters (see: Predicting Natural Disasters and Humanitarian Crises through GIS).
  2. The system also comes in handy when authorities want to discover any potential wetlands that need to be protected from the harmful effects brought about by pollution.
  3. Companies also take advantage of the GIS so that they may be able to choose a strategic market location that has not yet been saturated by other competitors in the particular niche industry.
  4. Management personnel use this system also so that they can be able to locate areas that are bound to suffer from catastrophes with regards to the infrastructure that is in place there.
  5. Any potential spread of diseases & other such like pandemic are usually limited by the use of the GIS since the patterns of their occurrence is predicted in sufficient time.

For more detailed articles highlighting how GIS is used in many industries visit:

Spatial Analysis

The real power of GIS, however, is through using spatial and statistical methods to analyze attribute and geographic information.  Analyzing and mapping geospatial data is used to provide insights into that wouldn’t be obvious by looking at the records of a database or spreadsheet.

The end result of the analysis can be derivative information, interpolated information or prioritized information.  Data layers are analyzed in order to answer different spatial questions. GIS maps are then produced that visualize the analyzed GISdata.

Some examples of the types of questions that GIS is used to answer might be:

GIS Cartography

The end product of any GIS analysis is typically a map. This could be a printed map or an online mapping product like ArcGIS Online.

Frequently asked questions (FAQs) about GIS

Getting starting in GIS? These GIS FAQs (frequently asked questions) can provide pointers to learning GIS, building a GIS career, finding a GIS job, and other topics involving cartography, geospatial technologies, and maps.

Frequently asked questions answered in this section:

  • Are GIS and geospatial the same?
  • What are the different types of GIS data?
  • What is the difference between a certificate and certification in GIS?
  • How do I get a GIS job?
  • What programming languages should I learn?
  • Learning GIS questions
    • How do I start learning GIS?
    • What else can help me find my way in GIS?
    • GIS seems powerful. Where can I find examples of what it can do?
    • How do I keep up with what’s going on in GIS?

Are GIS and geospatial the same?

There is an increasing trend to use the term geospatial instead of GIS.  So, what is the difference between geospatial and GIS?  

Although some may use the terms interchangeably, there is a distinct difference between the two in that GIS refers more narrowly to the traditional definition of using layers of geographic data to produce spatial analysis and derivative maps.  

Geospatial is more broadly use to refer to all technologies and applications of geographic data.  For example, popular social media sites such as Foursquare and Facebook use “check-ins” that allow their users the ability to geographically tag their statuses.  While those applications are considered to be geospatial, they don’t fall underneath the stricter definition of what makes up a geographic information system.

More: What’s is the Difference Between GIS and Geospatial?

What are the different types of GIS Data?

GIS data, also referred to as geospatial data, can be split into two main categories: vector and raster data.  Vector data is data that is represented as either points, lines, or polygons.  Raster data is data that is cell-based such as aerial imagery and elevation data.  More: Types of GIS Data Explored: Vector and Raster

What is the different between a certificate and certification in GIS?

Although the terms seem similar, a certification in GIS is an acknowledgement of proficiency in one or more areas of GIS, usually obtained through taking an examination.  

For example, the most common general certificate in GIS is the GISP, offered by the GIS Certification Institute (GISCI).  Esri offers a serious of certification exams for its various software products.  

A certificate in GIS typically achieved by taking short series of GIS related courses from an educational institute, culminating in that institute offering a piece of paper acknowledging competition of the course.   A certificate in GIS is not a degree but often employers might accept a certificate in GIS in lieu of a degree in a geography or GIS related major.  

More: GIS Certification versus Certificate Programs.

How do I get a GIS job?

Beyond taking coursework GIS, cartography, and programming, there are several strategies you can employ as you seek a career in GIS.  To learn more these articles are recommended: Building a GIS CareerTilting the GIS Job Hunting Odds, and Ten Tips to Prepare for a GIS Job Interview.

What programming languages should I learn?

Python is the most common language for scripting in GIS, used by both ArcGIS and QGIS.  There are other languages and scripting languages you can learn to round out your skills as a GIS developer: Learning GIS Programming

Learning GIS

Q. How do I start Learning GIS?

A.There are many places and ways to start learning GIS. If you want to try learning on your own start by taking online GIS Tutorial course. For a more guided independent study course you might want to explore Distance Learning. More and more institutions are offering on-site GIS courses and certification.

Q. What else can help me find my way with GIS?

A.Check out the Reference Center. Listed there are links to bibliographies, dictionaries, guides to software and more.

Q. GIS seems powerful. Where can I find examples of what it can do?

A.Try the Subjects and Industry category for case studies of the application of GIS. You can also browse through Bibliographies to find articles on GIS.

Q. How do I keep up with what’s going on in GIS?

A. There are a host of ways to stay up to date on trends in GIS and geospatial technologies. In addition to reading through articles on sites like GIS Lounge, you can track relevant posts on social media, attend GIS conferences to hear about what other people are doing, and find local GIS user groups.

GIS Career and Jobs

Q. How do I get into GIS?

A.The field of GIS requires many different skills in a variety of areas. To find out what these are check out my article on “Building a Career in GIS”

Q. Where can I look for a job in GIS?

A. Once you’ve got your resume ready start searching for GIS jobs you can apply to.

Q. How much can I make?

A.Find out the salary ranges for a GIS position in your area with the salary survey links.

GIS Data

Q. Where can I find GIS data?

A.There are a lot of GIS based data sources available on the web. You’ll find resources listed here.

Q. What if I can’t find the data I’m looking for?

A. Exchange of information is a very highly supported practice in GIS. Try posting your needs on one of the Discussion and Mailing Lists

GIS Software

Q. How do I find out about GIS software?

A.Consult my summation of the GIS software applications currently available.

GIS Programming

Q. I want to develop some GIS applications and I need some help!

A. A good starting place for learning about GIS programming is on this page.  

Quotes on “What is GIS?”

“In the strictest sense, a GIS is a computer system capable of assembling, storing, manipulating, and displaying geographically referenced information, i.e. data identified according to their locations. Practitioners also regard the total GIS as including operating personnel and the data that go into the system.” ~ USGS

A geographic information system (GIS) is a computer-based tool for mapping and analyzing things that exist and events that happen on earth. GIS technology integrates common database operations such as query and statistical analysis with the unique visualization and geographic analysis benefits offered by maps.” ~ Esri

“GIS is an integrated system of computer hardware, software, and trained personnel linking topographic, demographic, utility, facility, image and other resource data that is geographically referenced.” ~ NASA 

A geographic information system is a special case of information systems where the database consists of observations on spatially distributed features, activities or events, which are definable in space as points, lines, or areas. A geographic information system manipulates data about these points, lines, and areas to retrieve data for ad hoc queries and analyses” (Kenneth Dueker,Portland State University, 1979).

GIS has already affected most of us in some way without us even realizing it. If you’ve ever used an Internet mapping program to find directions, congratulations, you’ve personally used GIS. The new supermarket chain on the corner was probably located using GIS to determine the most effective place to meet customer demand.

A Short History of GIS

One of the most famous early examples of spatial analysis can be traced back to London in the year 1854 when Dr. John Snow using disease mapping to publish his interpretation of the source of a cholera outbreak (More: John Snow’s Cholera Map using GIS Data).

The map that Snow came up with was very interesting in that it had the capability of analyzing the phenomena relating to their geographical positions and this was the first time the world was witnessing this.

Photozincography was developed in the earlier years of the 1900s and this enabled the maps to be divided into various layers as required. In the initial stages, the process of drawing these maps was lengthy since it involved free hand but this changed later on with the introduction of the computer.

a black and white map from the 1850s showing London.
John Snow’s 1854 Cholera Map.

The first GIS was created by Dr. Roger Tomlinson and then introduced in the early 1960s in Canada. This system was designed to assist the Canadian government in managing land resources and planning for the future. CGIS allowed for the digital storage and manipulation of geospatial data, laying the groundwork for modern GIS.

Prior to this, mapping by the use of computers was being used for such cases but this is a method that had numerous limitations associated to it. By the end of the 80s period, the use of GIS had already become popular in other related fields which is why it led to a spur in the growth of the industrial sector.

Esri produced the first commercial GIS software with its introduction of ARC/INFO in the early 1980s. The introduction of ArcView, a Windows-based and more user intuitive desktop application for viewing geospatial data and mapping maps, helped to bring GIS into the mainstream.

(Fun fact: ESRI is an acronym for Environmental Systems Research Institute. Prior to 2010, ESRI was pronounced alternatively as E-S-R-I (pronouncing all the letters) or as “ezree”. In 2010, the company change the spelling from all uppercase letters to Esri and officially declared the pronounciation as “ezree” to promote the goal of “growing Esri’s name globally.”)

Since then, GIS and other geospatial technologies such as LiDAR, advanced remote sensing instruments on satellites, and drones have propelled the use of GIS into multiple areas.

Learn more: History of GIS

Components of GIS

The next step in understanding GIS is to look at each area and how they work together.  These components are:

  • Hardware
  • Software
  • Data
  • People


Hardware comprises the equipment needed to support the many activities needed for geospatial analysis ranging from data collection to data analysis. For desktop GIS, the central piece of equipment is the workstation, which runs the GIS software and is the attachment point for ancillary equipment.

The use of handheld field technology and mobile GIS is also becoming an important data collection tool in GIS. With the advent of web mapping, web servers have also become an important piece of equipment.


Different types of software are important. Central to this is the GIS application package. Such software is essential for creating, editing and analyzing spatial and attribute data, therefore these packages contain a myriad of geospatial functions inherent to them.

Extensions or add-ons are software that extends the capabilities of the GIS software package.

Component GIS software is the opposite of application software. Component GIS seeks to build software applications that meet a specific purpose and thus are limited in their spatial analysis capabilities.

Utilities are stand-alone programs that perform a specific function. For example, a file format utility that converts from on type of GIS file to another.

There is also web GIS software that helps serve data and interactive maps through Internet browsers.


Geospatial data is the core of any GIS. There are two primary types of data that are used in GIS: vector and raster data. A geodatabase is a database that is in some way referenced to locations on the earth. Geodatabases are grouped into two different types: vector and raster.

Vector data is spatial data represented as points, lines and polygons.  Raster data is cell-based data such as aerial imagery and digital elevation models

Coupled with this data is usually data known as attribute data.  Attribute data generally defined as additional information about each spatial feature housed in tabular format. Sometimes attribute data is stored separately in a spreadsheet file such as Excel or Google Sheets. Attribute data is linked back to geospatial data by relating unique values found in the same populated column in the GIS dataset and the attribute data.

In a GIS, each piece of data contains a geographic location and attributes.
In a GIS, each piece of data contains a geographic location and attributes that describe it.  The red dot on the map is a Fortune 1000 company headquarter and the attributes are displayed in the information window. Map: Caitlin Dempsey.

Documentation of GIS datasets is known as metadata.  Metadata contains such information as the coordinate system, when the data was created, when it was last updated, who created it and how to contact them and definitions for any of the code attribute data.

There are many different ways that GIS data can be collected.  Head up digitizing (the process of tracing GIS data directly on the screen), LiDAR, drones, GPS, and satellites are some of the ways GIS data is created.

Layers of GIS Data
GIS data layers. Source: FCDC


Well-trained GIS professionals knowledgeable in spatial analysis and skilled in using GIS software are essential to the GIS process (More: Building a GIS Career).

There are three factors to the people component: education, career path, and networking. Taking the right combination of classes, seeking a GIS internship, and attending conferences can all help someone seeking to build a career in GIS. 

Selecting the right type of GIS job is important.  A person highly skilled in GIS analysis should not seek a job as a GIS developer if they haven’t taken the necessary programming classes. 

Finally, continuous networking with other GIS professionals is essential for the exchange of ideas as well as a support community.

This article was first written on March 16, 2002 and has since been updated.

Further reading:

Photo of author
About the author
Caitlin Dempsey
Caitlin Dempsey is the editor of Geography Realm and holds a master's degree in Geography from UCLA as well as a Master of Library and Information Science (MLIS) from SJSU.