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What is GIS



What is GIS.


In the early nineties, I was just starting to learn GIS, making the transition from the CAD world. ESRI’s Arc Info software with its data model known as “coverage”, consisted of a complicated command line and primitive graphic user interface that was intimidating and elaborate. Its projection and topology concepts appeared restrictive and unnecessary. I could make maps in CAD with no other restrictions than those set client who only required that they were legible and that the text and lines drawn to scale.

One of our biggest clients at the time had decided to adopt GIS technology to meet the ever increasing need to standardize and share data across the organization. With an emphasis in accurate measuring land use acreages tied to permits from state and local environmental agencies as well as providing the base for accompanying hydrologic studies and land reclamation activities.

As a consultant, I was provided with data in the form of topography, land use boundaries, etc. With this data I worked on small and isolated projects that when completed were given back to our client in a CAD format for a dedicated GIS Technician to convert to coverage format and incorporate it into “seamless” datasets. It was an inefficient and tedious process that required a lot of editing and cross checking of topology to making sure field data types and names matched.

Transitioning to GIS was inevitable if we wanted to continue doing business with our client. As a result, I talked to my boss about implementing some sort of GIS system that the small company could afford. He asked me what GIS was. The answer that came to mind was: “It is Dynamic Mapping” to which he replied: “Dynamic mapping? That is mouth full”.

Up to this time, my exposure with GIS was limited to colorful maps with a north arrow, graphic scale, and neat map legend created through scripts written in AML and created by GIS super heroes, whose skills I aspired to acquire one day in the future. Little did I know how steep the learning curve was, but “Dynamic Mapping” was how I envisioned using GIS. The goal was to create maps from data I generated without the time-consuming task of experimenting with line width, text type and size, and a consistent map legend.

Of course, now we all know GIS systems can do more than simply create maps.

A common definition of GIS is, “systems designed to input, store, edit, retrieve, analyze, and output geographic data and information.” (Demers, 2005) GIS is composed of a well-orchestrated set of parts that allow it to perform its many interrelated tasks. These parts include computer hardware, space, and organizations, data, and information upon which the system operated, clients who obtain and use the products, vendors who supply the hardware and software, and other systems (financial, institutional, and legal) within which GIS functions.


The primary task of a GIS is to analyze spatial references between data and information. To perform meaningful analysis requires that the software be capable of performing many other tasks such as input, editing, retrieval and output. Still to this day, classifying the analytical and modeling capabilities is the strength of GIS.

The software contains algorithms and computer code designed to:

1. Organize geographic data within appropriate referencing systems.

2. Selectively query those data an aggregate them for easy understanding.

3. Count and measure both individual objects and collections of objects.

4. Classify and reclassify objects based on specified properties.

5. Overlay related thematic map data.

6. Be able to combine these individual techniques into ordered sequences of operations designed to simulate natural or anthropogenic activities for decision making.

These tasks tend to involve, either directly or indirectly, some form or mapped data.


What I called Dynamic Mapping was more likely CAC (Computer Aided Cartography), a step above CAD (Computer Aided Drafting) but certainly not even close to a GIS (Geographic Information Systems).


Products from these systems can look identical to both casual and trained observers. It is easy to assume that they are – with minor differences- the same thing.


CAC systems, computer systems designed to create maps from graphical objects combined with attribute, are excellent for display but lack the analytical capabilities of a GIS. Likewise, for pure mapping purposes it is highly desirable to use a CAC system developed specifically for the input, design, and output of mappable data rather than working through the myriad analytics of a GIS to produce a simple map.

CAD – a computer system developed to produce graphic images but not normally tied to external descriptive data files – is excellent software for architects and engineers, speeding the process of producing architectural or engineering drawings and simplifying the editing process. It would not be capable of analyzing maps – the primary task of the GIS. Over time, as these technologies matured however, we are finding a large crossover of techniques and capabilities, thus blurring the definitional lines among them.


“Dynamic Mapping” resembled a CAC and not a GIS. I needed to make and update maps faster and more efficiently but did not have neither requirements nor knowledge of GIS analytical process and capabilities.


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