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Surveying GIS

December 21, 2000
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The first thing I did after accepting the invitation to write about GIS for POB was to go through some boxes of old POB issues to see what had been written before. I worked my way through the 1990s and the ’80s. After I evaluated the material, I concluded that the best place to start was, where else? At the Point of Beginning.

Introduction

This is the first in a series of articles designed to introduce the concepts and issues of Geographic Information Systems (GIS) to surveyors interested in expanding their business and professional horizons. Together we will try to explore both the business and technical side of this interesting, exciting and complex revolutionary development in the surveying and mapping industry.

I have been working as a full-time GIS program administrator for over four years now. But, I began the journey to my current situation on a fateful day in 1975 when I got my first programmable calculator. I learned to program the 49 available lines to make a Hewlett-Packard 25 hand-held calculator lay out circular curves and perform radial stakeouts. I was pleased to be liberated from carrying eight place table books around, but I was frustrated by the need to enter the same data repeatedly instead of having a place to store it. Then there were the reams and rolls of documents and plans I had to trundle around and rifle through to locate needed information. “What if,” I thought as I pondered over a keystroke, “there was a way to organize all of this data in one convenient place and call it up at the touch of a button whenever needed?” I didn’t know it at the time, but that was the moment my career path changed direction and led me toward what eventually became known as GIS.

ArcExplorer allows users to view and query a large variety of spatially defined data files.

What is this phenomenon called GIS?

GIS is defined by ESRI (Environmental Research Systems Institute, Redlands, Calif.) as “Geographic Information System: an organized collection of computer hardware, software, geographic data and personnel designed to efficiently capture, store, update, manipulate, analyze and display all forms of geographically referenced information.”

The concept of developing a commercial GIS product is generally attributed to Jack Dangermond who founded ESRI in 1969. It was not until 1981 that the first GIS software package developed by ESRI, ArcInfo, went to market. The ArcInfo of 1981 ran on minicomputers, very often DEC (Digital Equipment Corporation) hardware and a VAX operating system. Shortly thereafter, its deployment envelope expanded to include the UNIX platform.

In the mid-1980s, Intergraph Corporation (Huntsville, Ala.) emerged as the market leader in the field by correctly recognizing the importance of integrating its CADD systems with its GIS product line. Intergraph products of this era ran on proprietary UNIX “Clipper” workstations. These products were marketed as integrated hardware/software packages.

It takes only a single word to describe the next generation of CADD and GIS products and their impact on the marketplace: Microsoft. AutoCAD began offering PC versions of its drafting and design package in the late 1980s. By 1993, it abandoned its UNIX roots, began acquiring its third-party extensions and offered a Windows 3x version. In 1994, it offered ADE, AutoCAD Data Extension, an early attempt to develop a desktop GIS solution.

Autodesk (San Rafael, Calif.) today offers AutoCAD Map 2000i, a fully functional desktop GIS product as part of its product suite, and AutoDesk Map Guide, its web-based development line. Autodesk World, a full spatial database management tool, is still offered but seems to have something of an uncertain future at the moment.

ESRI first offered PC ArcInfo in 1986. In 1991, it made its first try at desktop GIS when it released ArcView. By the time ArcView Version 3.0 rolled out in 1995, GIS was fully functional on the desktop. Still, ESRI released a UNIX version of ArcView. Intergraph was at first somewhat hesitant to shift the bulk of its product line to the Microsoft platform. In corporate terms, it “blinked.”

In 1996, ESRI released ArcInfo for Windows NT, completing the Microsoft paradigm shift. That same year, it launched MapObjects, a set of developer tools that utilizes an Active X environment to serve up web-based mapping products.

Today, ESRI is considered the world leader in GIS products and services. It reigns supreme on the desktop and the Web. Intergraph is still firmly in the number two position with its new Microsoft-based GeoMedia “Open System” product line. Most of its client base is still large government and corporate organizations. And it recently sold its MicroStation civil line to Bentley Systems (Exton, Pa.), now ranked third in market share.

The Macintosh platform has never been a significant presence in GIS.

There are also now, aside from the smaller market share GIS companies, hundreds of third-party software vendors whose products interface with the market leaders in the field. Market analysts place annual sales revenues for GIS and related products at just shy of one billion dollars.

The explorer view with data from the FEMA website including a TIFF image.

FAQs:

What exactly is a GIS and what does it do?

Earlier I quoted the ESRI definition of GIS. Now let’s try to break it down into its components. A GIS is what is called a spatial database. What that means is that the attributes contained in the database are linked to a specific location. That “real world” location is also defined in the database by a process called georeferencing, the GIS term for coordinates. The user can display a graphic representation of the data, and develop queries and reports from specified data layers. GIS layers are usually constructed with data grouped by specific unique subjects.

Spatial data can be raster, vector or 3-D models. Orthoimagery of large areas is becoming increasingly more available in GIS databases.

What is the difference between CADD (Computer Assisted Drafting and Design) and GIS?

The major differences between these two are function and file structure. A GIS is most often used for analysis and planning purposes. A CADD system is chiefly used for designing. A CADD drawing file contains layers, entities, properties and attributes. The database is in fact contained within the drawing file. The attributes are independent of the spatial properties. The support files do contain data, but the parent file is the drawing. A GIS is a database. The “layers” reside in the database. A map produced from GIS data is a graphic representation of elements contained in that database. Multiple users can produce maps and reports from the same relational database, but a GIS produced map cannot be “exchanged” like a drawing file. You must have access to the database to produce a map. Edits are made to the database, not the map.

CADD products can perform some spatial queries, but attributes are separated from property entities. A GIS product performs spatial queries, searches, sorts and generates reports. Attributes are linked to properties and move with them. One GIS database is capable of covering an area of any size as opposed to a group of CADD files that are not necessarily contiguous. CADD and GIS are different environments, and the use of one does not necessarily supplant the need for the other. It is important to understand both the differences and the similarities. Interchanging data between the two environments can leverage project efficiency on a grand scale when this concept is fully understood.

How expensive and difficult is it to start using GIS?

How about free? That is providing you have a Windows 98/2000/NT-based PC and an Internet connection. The URL http://www.esri.com/software/

arcexplorer/index.html takes you to the ESRI website where you can download its free GIS data viewer ArcExplorer2.

Now about the degree of difficulty; the program needs about 20 Mb of hard drive space. Download takes about five to 15 minutes depending on the speed of your Internet connection. ESRI asks you to fill out an online registration form before you download. It’s advisable to create a folder for the file in advance called “ae2setup.exe.” Then using “My Computer” or “Windows Explorer,” simply click on the file. To make it easy, simply accept the defaults. After restarting your computer, the blue, green and yellow globe icon should appear on your desktop.

The top row of the opening screen contains pull-down menus. The next two rows are “buttons” representing shortcuts to most of the same functions contained on the pull-down menus. The first button we will explore is the large “+” slightly to the left center of the middle row. This is the “Add Theme” button. “Theme” is an ESRI GIS term that generally means layer. ArcExplorer 2 works best with ArcInfo Coverages and ArcView Shape Files. It does, however, support a broad range of file formats like DXF, DWG, DGN, GIF, TIFF, JPEG and many more. When you click the “+” button, the navigator appears.

Most of the 10 plus megabytes in the executable download file ends up in a directory called “esridata” (see figure on page 60). Clicking on any of the folders in the left window will cause all the viewable files to appear in the window on the right. Select any file(s) and click the “Add Theme” button. The names of the selected themes appear in the window on the left-hand side of the interface. This is called the “Explorer View.”

The small white boxes on the upper left part of the theme toggle the themes on and off in the “View” window. Checking the box draws the theme on the map view. Unchecking the box turns it off. The “draw order” of the themes is from bottom to top as they appear in the Explorer View. Clicking the mouse in the gray area by a theme’s name causes it to become “active.” A box or “button” will appear around the theme that is active. This is the theme that can be “queried.” Only one theme may be active at a time. ArcExplorer performs two kinds of queries. The simple query is performed by the “identify” feature, the lower case “i” button on the bottom row. The user can click his or her mouse on a feature on the active theme and a message box will appear displaying the attributes. The “Query Tool” (Hammer Icon) can perform full searches and will be covered in more depth in another column.

If you have some CADD files or image files on your computer, open a new view by clicking on the first button on the left-hand side of the middle row. (The standard Microsoft icon for new document.) Then click the Add Theme (+) button. Navigate to the directory where your CADD files are stored. If ArcExplorer supports the file type, the file names will appear in the right-hand box of the navigator. There is one caveat here. For the displayed files to have correct spatial relationships with each other, they must all be a common horizontal datum.

ArcExplorer is a data viewer. It allows users to view and query a large variety of spatially defined data files. It does not allow the user to edit data or build datasets. Click the “Help” button and read through the “Contents” section for a complete description of ArcExplorer’s full range of functions. (It doesn’t take long.) In the next column (April) we will examine the makeup of the GIS user community and take a tour of ESRI’s GIS desktop product, ArcView.

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