Readings:

Scan the intro section in the Help portion of ArcGIS. It will be quite helpful to do this before tackling the exercise.

Some introductory thoughts: Academic/disciplinary tribes exist and they fight over territory. GIS as a relatively new and evolving endeavor, is in the midst of such turf battles. This is evident in the 4 -5 different descriptions of GIS in Clarkes (2001) intro to GIS text, but also in many other ways. As my one advisor used to say, "where there are 3 people there are politics". I mention it here because if you are aware of this turf battle you can avoid it; it produces few solutions to answers, and produces mainly intractable behavioral problems. The debate on what GIS is or should be can get acrimonious. Perhaps, better questions to concentrate on are as follows. Can GIS be helpful in solving a particular problem at hand, or what types of problems can it solve? What types of insights can it bring to light? How can the data be 'visualized' and/or analyzed best in different circumstances? What are its limitations? What is the quality of the products produced with it? It may simply be that GIS is an integrative computer representation and/or model and/or analysis of some part of the universe with a map perspective, but that description covers a lot of ground. Another description may be that it is a software environment made of map layers with map elements linked to relational databases, coupled with analytic tools. One think is clear, it is being utilized more and more.

GIS software architecture components: One way to define GIS is by what the software does. The following is a list of common components:

• Relational database with ability to query (DBMS - Data Base Management System).
• Vectors based graphics/cartographics package.
• Statistical analysis and graphing package.
• Modeling packages (e.g. surface contouring).
• Raster based image display and modeling.
• These components are linked.

Key aspects of GIS packages:

• Features with attributes. Point, line and polygon features are three basic types of elements used to represent real world features, such as volcanic centers, rivers, and the map expression of a geologic unit..
• Various components are linked, e.g. fields in the database are linked to polygons in the graphics mode. Change the field, and the feature is plotted changes.
• A primary way of working with the data is through maps instead of lists and tables.
• Ability to modify and query on the basis of feature attributes (often referred to as classification).
• Raster vs. vector distinction is important here.

Language as key: There is a lot of new language in GIS. Some of it is specific to a given software environment. Below are just a few terms as examples of how a word takes on a new specific meaning.

• Arc - a linear feature in a GIS (and not particularly arcuate), stored in vector mode with traits such as endpoints, thickness and color.
• DBMS - Database Management System.
• Geocoding: where information is attached to feature elements. In this way with a simple point and click on the feature you can find the address.
• Metadata ­ data about data. Basically descriptions of what is in a database, how it was obtained the quality of the data.
• Record - a row of data in a table, the attributes for a feature.
• Theme ­ in context of ArcView it is a feature and its attributes together (i.e. a shape and a database file). Geographic boundaries and soil type would be two different themes you could explore. Each theme can also be thought of as a layer.

A quick history of ESRI GIS products.

ArcInfo is the original industrial strength GIS package. It runs on UNIX and PC platforms, and has a long learning curve associated with it, and therefore is used by a relatively select few. You can read ArcInfo files with ArcView or ArcGIS, and there are a lot of ArcInfo data sets available on the web (including for Nebraska - from CALMIT).

ArcView. At first this was meant as a more user friendly GUI for ArcInfo files, so that a much wider audience could view and manipulate ArcInfo generated products. With each version ArcView became more of a stand alone application. It is still much more limited in its potential than ArcInfo, but for smaller more limited projects it is quite useful. What ArcView demonstrated is that there was a much larger audience out there for something more user friendly. ArcView is present widespread use.

ArcGIS is the new arrival, and is a PC based package that is meant as a fairly powerful, stand alone GIS (so that Arc Info is not a necessary companion as it was with ArcView). Much of what was in ArcView is now in an internal component of ArcGIS, called ArcMap. ArcGIS uses Visual Basic for Applications as a customization language instead of Avenue, and so many companies with vested efforts in ArcView, have not switched over, but will likely do so in the future.

There are other GIS packages out there! ESRI dominates the market at present, but it is useful to learn the basic ideas and skills that can be carried from one software platform to another.

Three levels of learning the software:

• Level 1: Navigating around so that you can see what information is available in a GIS database.
• Level 2: Modifying an existing project to produce new products.
• Level 3: Creating a new project.
• Level 1 is a breeze and we will accomplish this week. Level 2 we can touch upon. Level three needs a bit more work.

Some types of ArcGIS files: (files are identified by the .suffix.)

• .mxd - this is a saved map document, complete with the various layers, saved in ArcMap.
• .shp ­ these are shape files. They keep the vector information to draw features and the links to attributes.
• .dbf ­ these are database files. They are the tables of attribute information for a given type feature.
• ArcGIS creates many files so file management is a significant issue.

ArcGIS components:

• ArcCatalog: for managing, browsing, and preliminary viewing of your data.
• ArcMap: for plotting, analyzing, editing, querying, charting, and classifying data.
  • data view vs. layout view.
  • layers in a data frame and depicted in map window.
• ArcToolbox: data conversion, modeling and spatial analysis tools.

References:

• Bartier, P. M. & Keller, C. P., 1992, Geographic Information Systems Capabilities for the Earth Sciences; Journal of Geological Education, v. 40, p. 360. This is getting a bit dated but is a worth a quick read through.
• Clarke, K., C., 2001, Getting Start with Geographic Information Systems; Prentice Hall, 352 p.
• Hutchinson, S. & Daniel, L., 1997, Inside ArcView GIS, 3rd edition, OnWord Press, 488 p.

Copyright by Harmon D. Maher Jr.. This material may be used for non-profit educational purposes if proper attribution is given. Otherwise please contact Harmon D. Maher Jr.