Step 0.  An introduction to GIS, ArcView projects, and basemaps.

Geographic information systems have the ability to display layers of spatially referenced information.  One of the most useful applications in plant disease management work is the display of point data as a layer over other layers showing background information or baseline data.  In the example below, the location of Aspergillus flavus samples sites (black points) and interstate highways (red lines) are layers ready to be placed on top of a map of Arizona showing the county boundaries (polygons).

Combining the layers you get a map that looks like this:

 

Information about GIS and sources of data for base-map layers are widely available on the internet (see references).

In ArcView, all of the work is organized in a Windows environment that is call a "project".  Layers of spatially referenced data are displayed as "Themes" in windows  called a "Views".  Tabular data are displayed in windows called "Tables".  An ArcView project is saved as a ASCII  file that organizes the geographic data that you bring together in ArcView. ArcView project files have the extension .apr attached to the file name.  It is important to remember that the geographic data (explained below) are not actually stored in the project ".apr" file.  Instead, the ".apr" file contains pointers to the data files using the DOS path name telling ArcView where the files are located.  When you open an existing ArcView project, ArcView gathers all the data pointed to and displays the result on the computer screen. 

Because ArcView projects contain pointers to data files, in using ArcView, it is best not to move your geographic data files to different locations (folders or subdirectories) on the hard drive, because the pointers in the ArcView project files will not be able to find them.  It is very helpful to come up with an organization of your geographic data into folders (subdirectories) that you are comfortable with and stick with that organization.

When ArcView is started from MS Windows by double clicking on the ArcView icon, the ArcView project window appears.

Note that on the left panel is a list of five types of documents that can be included in a project.  We will be primarily concerned with "Views" and with "Tables". For this example, choose to create a new project as a blank project (or press cancel) which get you to the same place.

We want to display our sample locations on a base map showing roads, county boundaries, rivers, etc.  The base map will be displayed in a particular coordinate system.  The goal is to have a point map of our sample locations in the same coordinate system as the base map. The first step, therefore, in displaying a map of sample points, is to display an appropriate base map.

For baseline data in Arizona, we use data from The Arizona Land Resource Information System (ALRIS).  With ArcView 3.2, ESRI provides a set of five CD's with baseline data from all over the world that we use for baseline data for areas outside of Arizona (details).

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