GIS

Introduction

ArcGIS® is a desktop mapping program produced by ESRI (Environmental Systems Research Institute, Inc.) that allows you to create your own maps from scratch starting with geographic data in electronic form. There are several interrelated component programs, the basic ones being ArcCatalog, ArcMap, and ArcToolbox.  These three components comprise what is now known as ArcGIS Desktop, or ArcView.  When other advanced components are added, it comprises ArcGIS Workstation, or ArcInfo.

It is a complex program.  This guide will give a skeletal description of the program and will point you in the right directions for more help, but can't begin to explain how to use the program. Users need to be familiar with Microsoft Windows® and must be willing to spend some time to learn how to use ArcGIS.  Facility with a spreadsheet or similar program (e.g., Excel) is also useful for working with data.

Locations

1. The Data Services & GIS cluster on the first floor of Perkins Library.  The ArcGIS 9 program is loaded on the hard drives on several computers here.

2. The software is also available in 2 OIT labs:  in the Technology Alcove in the Library's Lower Level connecting corridor between Bostock and Perkins, as well as in the OIT lab in Old Chem 01.

3. The software is site licensed, and users can get a free copy to use with certain restrictions: "ArcGIS is distributed free for use on university-owned machines only .... Requests must be placed online and user will be required to pick up free CD's to install the software."

Help Availability

The following options are available for obtaining help and learning about ArcGIS.  Books are located on the bookshelves near the computers in Data Services & GIS cluster.

The following books are based on ArcGIS version 9, the installed version.

• Getting to know ArcGIS desktop : basics of ArcView, ArcEditor, and ArcInfo  A tutorial-based introduction, using samples from the CD inside the front cover.

• Using ArcMap : ArcGIS 9  This is the primary manual to refer to for making a map.

• ArcGIS 9. Understanding map projections  Explains coordinate systems and geographic transformations, plus reference pages for each supported projection.

• ArcGIS 9. Geocoding in ArcGIS  Details on converting addresses to points on a map.

• Statistical analysis of geographic information with ArcView GIS and ArcGIS

The following books are based on ArcGIS version 8, which is generally very similar, so they can add insight.

• Getting Started with ArcGIS  Provides an overview of the program. No index.  Data that go with the examples can be found in the ArcTutor folder within the Shared Documents folder.

• Using ArcCatalog Explains the program used to manage the files that make up your project.

• Using ArcMap  This is the primary manual to refer to for making a map (in ArcGIS 8).

• Using ArcToolbox  Explains the utility program used for importing other formats, etc.

• Using ArcGIS Spatial Analyst  Describes use of an extension to ArcGIS that allows mapping of elevation data.

Online help:

Pull down the Help menu within ArcMap or press the F1 key to access extensive on-line help. You can also access Desktop Help directly from an choice in the ArcGIS folder.

• ArcGIS Introductory Tutorial, University of Arkansas Libraries
  Highly recommended!  An excellent overview of ArcGIS 9, with lots of screen shots.  Sections 1 and 2 provide enough information to produce a shaded map depicting demographic information.
• Specialized tutorials from the University of Michigan Libraries
  Includes topics such as changing the projection or manually georeferencing an image. Of special interest is the guide on the location of geoprocessing tools from ArcGIS 8 in the ArcGIS 9 Toolbox.
• Mapping Crime: Principle and Practice A nice overview to social science thematic mapping from the U.S. Dept. of Justice.  From 1999, but the concepts are valid.

Layer Structure

ArcGIS uses the concept of a Geographic Information System (GIS) to build maps in which each category of spatial feature is a separate layer. The layers are spatially "registered" so when the user overlays them the program can line them up correctly  to build a map. There are several types of layers, and the user has many choices regarding how to depict them:

• Point (e.g., buildings, landmarks).  Zero-dimensional.

• Line, or arc (e.g., roads and streets, streams, railroads, power lines). One-dimensional.

• Polygon (e.g., political entities, census geographies such as tracts). Two-dimensional.

• Raster images (e.g., an aerial photograph or scanned topographic map).  Useful as backdrops for overlaying other layers.

Data can be associated with the spatial features, and mapped or analyzed:

• There can be attributes, or spreadsheet data, associated with each feature in a layer (e.g., demographic data for each Census Tract).

• Data tables (e.g., database or spreadsheet files) can be added ("joined") to a layer if there is a common field (e.g., census tract number).  The preferable format to use is dBase.

The program can also map spatially referenced data files in some spreadsheet and database formats (e.g, if one field contains latitude/longitude coordinates).  Tables that contain address data can be "geocoded" to map the locations on a street layer.  Advanced users can open a non-registered raster image and register it using the program's functions.

You can also add your own information to a map with drawing and writing tools.

Concepts and Terminology

Layer: The ArcView 8/9 term for a layer of information on a map (e.g., census tract polygons). These were called "themes" in ArcView 3.x.  Layers are registered, meaning the program knows their location in physical space and can thus overlay them correctly to make a map.

Features: The individual elements in a layer, either points, lines, or polygons as described above. Individual features can be selected to use in data analysis and processing (e.g., combining, saving as a new layer).

Data Frame: A window on the monitor that consists of a map, made up of one or more layers.  One frame can be shown at a time in a data view. Multiple frames can be shown at once in a layout view.  All the layers in a data frame will need to use the same projection and datum.

Element: A label, title, or other such graphic added to the data frame (e.g., the labels to each feature).  Individual elements can be selected and moved, deleted, resized, etc..

Data View:  The view where you build your map and analyze data.  If your project requires several maps, you can have multiple data frames, but only one visible ("active") at a time in the data view.

Layout View:  A view where you can better organize your map elements to look nice for printed output or for exporting as a graphic file. You can display multiple data frames in the layout view, along with other elements such as a legend, north arrow, scale, title, etc.

Table of Contents:  This is the legend that appears to the left of the map. Lists the layers open in that view and allows you to alter the look of the map by turning themes on and off and by changing their appearance.  The "display" tab shows the layers that are available for display on your map.  The "source" tab indicates where these layers are located on your hard drive, on a remote server, on a CD, etc.

Layer On/Off  If the box to the left of the layer's name is checked, the layer is turned on and displays in the data frame (i.e., on the map).

Map Document: The document in which all of the information with which a user is working, in it's current form, is stored (comparable to an Access Database or Excel Workspace).  This needs to be frequently saved (CTRL-S) to the user's personal directory.  Has .mxd filename extension.

Screen Layout

Tools display around the perimeter of the ArcGIS window or in a free-floating box.

When a tool icon is clicked, the pointer becomes that tool. The pointer will then perform that tool's operation when you click a location on a map.

Selection and resizing tools might open as a free-floating box, but you can drag and anchor it in the window above the map.

Drawing and labeling tools are available in the lower left corner of the window.

Remember that when you click on the map the pointer will continue to perform the selected tool's function until you click another tool icon.

File Formats

A thorough discussion of various formats that ArcGIS can read may be found in the online help. From the Help menu, choose ArcGIS Desktop Help..., then under the Contents tab choose "Data types supported in ArcGIS" from the Contents. Some common types of files are listed below.

Shapefiles:  The native ArcView 3.x format, these have the filename extension .shp. When you open one of these layers, it also uses several auxiliary files that are in the same folder as the .shp file (e.g., all related files are needed for the shapefile to open).  Probably the most common ArcGIS files freely available, and easy to work with.

Layer Files (.lyr extension):  Not a format that stores data, but used within ArcGIS 8.x and higher to store references (e.g., full path) to actual data (e.g., Shapefiles) and also to store how the data is displayed, associations, etc.

Coverages: ArcView will also read coverages in ARC/Info format, the full-feature GIS software package also manufactured by ESRI (now also called ArcGIS Workstation).  Each coverage is stored in its own unique folder. The folder's name is the name of the coverage; the files within each folder have standard names (arc, arx, pat, dbx, etc.).

ARC/Info Interchange (Export) Format: This format, whose extension is usually .e00, will need to be translated into ARC/Info coverages.  In version 9.x, access the the conversion utility by opening ArcCatalog and from the View menu add the "ArcView 8x Tools" toolbar.  This also provides access to utilities to convert from MapInfo or SDTS (Spatial Data Transfer Standard) files, among others.

Raster Image Formats: ArcGIS can open selected registered raster-scanned formats, such as certain JPEG files or the GeoTIFF format. Even if an image is not registered, they can be manually registered so you can overlay other layers.  See documentation or the University of Michigan's help guide.

ArcView Version 1 Views:  "Views" from ArcView 1.0  (filename extension .av) format can be opened by choosing Project ... Import in ArcView 3.0 (project window active).

Making a Map Step-by-Step

STEP 1:  Create a folder to save your files!   When downloading files, unzipping files, and temporarily saving your ArcGIS projects on the computers in the Library, please create a place to store your material:

1. You can create a folder named with your NetID or last name in the "Patron Data" folder of the "E:" (Data) folder on the hard drive. This "Patron Data" folder has a shortcut on the desktop.  This is only available in the Data Services/GIS computer cluster (Perkins floor 1), not in the other labs. You can later take your data with you by (a) saving it to a USB drive; (b) burning it to a CD; or (c) sending it to a remote computer using FTP (Start ... Programs ... F-Secure SSH Client ... F-Secure SSH File Trnasfer).
2. You can create a folder on the desktop of the computer, but this and its contents will be gone once you log out. You can later take your data with you by (a) saving it to a USB drive, or (b) burning it to a CD.
3. You can connect to your ACPUB user space by double-clicking the desktop icon "AFS Drive Map."  This creates several virtual drives:  your ACPUB root drive is P: and the AFSDocs folder within it is H:  The AFSDocs folder also appears as a shortcut on the desktop.
4. You can plug in a USB (i.e., "flash" or "memory stick") drive to the computer, which usually appears as the F: drive, and just use that to start with.

Since ArcGIS keeps track of where each file is, it's not advisable to move files around once you start working on a project. It can be tedious to tell the program where they've been moved.

STEP 2: Gathering Data: You need to gather your data and save it in your personal folder before ever starting the program.  Gathering the data and massaging it so ArcGIS is able to open and analyze it can be the most difficult part of any project.

FIPS County Codes:  Most Census data uses filenames based on the Federal Information Processing Standards (FIPS) codes as published by the National Institute of Standards and Technology. You can refer to the county codes at the NIST website.

For studying U.S. demographic patterns, see the guide on gathering census data, and other guides on the Census Bureau's American Factfinder and the CensusCD products from Geolytics. Besides what's mentioned in this guide, there is also a lot of basemap data in ArcView 3.x format (which ArcGIS 9 can use) on the five ESRI Data CD's in the CD cabinet.  Much data is available for download.  Also, many CDs from federal government agencies (USGS, etc.), located in the Public Documents CD Storage Cabinets on the 3rd floor of Bostock, contain files that can be read by ArcGIS.

STEP 3: Start the Program:

1. On the computers in the Library, double click the ArcMap icon on the desktop.

2. A popup will ask you if you want to open a new empty map or an existing map.

3. To add layers, click the yellow "plus" button (not the "plus" tool) or right-click on the "Layers" heading in the Table of Contents and choose "Add Data." Negotiate the file structure to find files or directories in one of the formats discussed below. You may need to click the "connect to folder" icon to access more folders.

STEP 4: Create Basic Census Data Map: (assumes you've collected some data)

A. Open boundary files.  Multiple sources for data. Two examples are:
 

B. Process boundary files as appropriate for your project

C. If you need to join data from a .dbf file (see Census Data guide), wait until after you've merged adjacent layers into a single layer (e.g., don't join data to the Edgecombe Co. attribute table if you plan on later merging it with Nash county in order to analyze the entire MSA).  Right click on the layer name, choose Joins and Relates ... Join.

D. Change the Symbology to depict demographic data on the map.  Use the layer's Properties dialogue (right-click on the layer's name in the Table of Contents) and choose the Symbology tab.  Quantities ... Gradated Color is often useful.  You will often want to normalize the value of a variable with a total for that geographic unit (e.g., normalize the number of rental units per tract by the total number of housing units per tract).

Census Feature Class Codes (CFCC's) are used in coding features within some layers, such as the various categories of streets, roads, highways, and freeways in street or road layers. Knowing the meaning of these codes can help in selecting or clearly displaying features in a layer.  List from ESRI.  Complete documentation from Census (CFCC's begin on page 3-25, or p.77 of the Acrobat document)

STEP 5: Exit:  After saving your work, choose Exit under the File menu.