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Getting Started in ArcGIS This series of pages explains the basics of ArcGIS, developed by Environmental Systems Research Institute (ESRI). It is not a comprehensive overview, since I have tended to focus on the topics I have found most useful in my own work, and neglected other topics. Rather, these pages are meant to give you a some familiarity with Arc's main functions and capabilities. Ultimately, however, you won't learn ArcGIS by reading about it; you will have to play with it yourself. So you should use these pages for quick reference as you experiment with the software. ArcGIS's dynamic menu structure and symbols may appear a bit daunting at first, but the on-line help utility is excellent. So jump in, explore the menus, toolbars and options, and experiment! The Pearson Hall GIS lab at the University of Delaware supports a
comprehensive set of ArcGIS modules and functions known as the Arc
"Desktop." ArcGIS is actually comprised of progressive "client"
packages. The first level is ArcView
(very similar to the old ArcView3) which offers basic
functionality in three function categories known as ArcMap (visualization), ArcCatalog (data handling) and ArcToolbox (spatial queries,
etc.). The second level is ArcEditor,
which adds geodatabase editing capabilities. The third level is ArcInfo which supports a full set
of geoprocessing functions. Don't worry about keeping these
straight; the transitions between them are pretty seamless. There
are also various extensions
such as Spatial Analyst which
supports raster functions, 3D Analyst
which supports three-dimensional modeling, and many others. Starting an ArcMap Session To start an ArcMap session, double click on the ArcMap shortcut icon. Start with a new empty map. Download and unzip some canned data to your data stick or an appropriate work directory. Click the "Add Data" button (plus sign on the yellow diamond) to start adding data layers to the empty "Layers" dataframe in your map (try counties.shp, lakes.shp, rivers.shp, and states.shp, holding down the Ctrl key so you can click on and load multiple shapefiles at once).
Your layers will be displayed in arbitrary colors in the map, points
on top of lines on top of polygons. The map paints each of
the checked layers in bottom-to-top order. To turn the display of
a layer on or off, click the check box. To hide or unhide a
layer's legend, click the plus/minus box next to the check box.
Right-click the icon below the layer name to select an alternate
display
color. If the legend is in "Display" mode you can rearrange the
display sequence of the different
layers by dragging a layer up or down in the legend box with the left
mouse button. Each of these layers includes the coordinate data used to display
the individual geographic features within the layer, as well as various
attribute data. For example, the States and Counties layers
include lots of census data on population, housing, etc. By
default, Arc will display all the features in a layer the same way, but
you can have the features represent the values of any attribute
field. An example is shown below. Getting Oriented  You can
pan or zoom your map any way you like via View--Zoom Data, or by using the
View Tools accessed via View--Toolbars;
simply check "Tools" (and notice how many other toolbars are
available!) Placing the mouse arrow over each tool identifies
it. The magnifying glass icons are interactive zoom tools: use
the mouse to drag a zoom rectangle on the map. The arrow-in and
arrow-out icons are fixed percent zooms. The hand icon is the
interactive pan tool. The globe icon sets the map to its full
extent. The left and right arrows access the previous and next
views. The outlined arrow is an interactive feature select tool:
click on individual map features or select all features within a drawn
rectangle. The black arrow is for selecting map graphic elements
such as titles, labels, etc. The information tool accesses the
data associated with any map feature you click on. The find tool
selects features with data records containing specified strings of
characters. The measure tool measures incremental and total
linear distances between successive points you click on the map;
double-click to terminate this tool. Zoom your map to the continental US only. To manage the display of an individual map layer, double-click on the layer name or right-click on the name and select "Properties." The most useful Layer Properties tabs: The "Symbology" tab accesses all the thematic controls for the layer, allowing you to set display styles for different feature categories. The "Source" tab tells you the layer's native coordinate system and directory path, The "Selection" tab lets you specify how selected features in the layer should be displayed; The "Display" tab lets you control the layer's degree of transparency. Basic thematic mapping Access the States shapefile's Layer Properties window and click the "Symbology" tab. The default displays all features with a single symbology. Click the symbol box to obtain a menu of color, fill and outline options, and start experimenting! Once you get familiar with how these work, give the States layer features black outlines and a transparent fill so that the States layer overlays the County layer but lets the county outlines and fill color show through. (If the legend is in "Display" mode you can drag the States layer above the Counties layer if necessary.) Select appropriate symbology for the Rivers and Lakes layers. Once you have changed the display of the other layers, try some fancier symbology with the Counties layer. Instead of simply mapping all counties features with a single symbol, you can map feature Categories by any attribute field, or map feature Quantities by any numeric attribute field. Or you can create little pie Charts to overlay each feature, showing relative quantities in several fields. Or you can map Multiple Attributes using overlay symbols of varying size, color, etc. The most useful option in the Show box is "Quantities," which lets you use graduated colors, graduated symbols, proportional (sized) symbols or varying dot densities to convey field values. Try creating a map showing the spatial distribution of elderly (65 or older) or blacks or Hispanics by county using graduated colors (some cool-to-hot color ramp). Double-click Counties, click the "Symbology" tab, pick "Quantities" and "Graduated Colors." In the "Values" pulldown menu in the Fields section, select whatever field you want to map. If you want to map percentage elderly, black or Hispanic instead of simple counts, select "POP1990" in the "Normalization" pulldown menu. Then pick a nice color ramp. Now you need to choose a classification scheme, and this is where you can "spin" the story your map is telling. Click the "Classify" box to access the Classification menu window. The default choice is "Natural Breaks," which is a often a useful compromise between "Equal Interval" and "Quantile." Specify the number of categories you want the counties grouped into; you can specify category ranges manually if you like. The histogram shows the distribution of counties across the range of data values. Click "OK" to close the Classification and Layer Properties windows, and you should now have a thematic map showing population densities by county. The three maps below illustrate three different classification methods applied to identical data. In each map the counties are assigned to 10 categories, and the same green-to-red color ramp is applied. The distribution of counties appears pretty normal (in the statistical sense) with few counties on the tails and most counties concentrated symmetrically around the mean.  The equal-interval mapping assigns most counties to mid-range categories, and has relatively low color contrast. On the other hand, the quantile mapping assigns 10% of the counties to each category, so the categories on the tails have much larger ranges than the categories near the mean, and the map may overdramatize the "geezer crisis" in the heartland (red is a good "crisis" color!). The natural breaks classification is a compromise. The point here is that your choices of colors and classification method really shape your map's message. Try out some of the alternative thematic mapping techniques: graduated symbols, dot-density, etc. Once you get an appealing thematic map created, you can Edit--Copy Map to Clipboard or File--Export it as a GIF image. To make this a proper map, you would need to add a titles, labels, north arrow, scale bar or ratio, projection information, legend, etc. You can add some these elements to your map in Data View. Others can only be added via the Layout View, which is ArcGIS's formal cartographic composition environment. You can switch between Data and Layout Views by clicking the little earth and page icons at the bottom left of your map. Note that the Layout View is live-linked to the Data View so that when you zoom or pan the map in the Data View, the map in the Layout View will be zoomed or panned the same way. To quickly label the features in a map layer using some attribute field, use the "Labels" options in Layer Properties. To add a data frame, text or graphics to your Map View, use the Insert menu. Anything you add in the map view will also appear in the Layout View. If you switch to the Layout View, the Insert menu also lets you add additional map elements such as title, neatline (box around the map), legend, scale bar, and north arrow or compass rose.  On-Line Help and Documentation ESRI provides pretty thorough
on-line help and documentation through the Help--ArcGIS Desktop Help
menu. You can access information via the Index, by simply typing
in a topic word or phrase; via the Table of Contents which has
extensive
information about ArcView organized in nested menus; or via the search
utility to access information by keywords or phrases. Rather than providing you with lots of step-by-step directions in
this course, I want you to explore this software and its capabilities
for yourself. Your initial progress may be a little slower, but
this exploratory approach will give you a better mastery of tools and
techniques that you can apply to your own projects later on. |
