Kristina Schneider, Francisco Olivera, and David R. Maidment
Center for Research in Water Resources
University of Texas at Austin
ArcGIS 8.1 is a software program, used to create, display and analyze geospatial data, developed by Environmental Systems Research Institute (ESRI) of Redlands, California. This exercise has similar goals to the parallel exercise, Introduction to ArcView 3, except that is uses the ArcGIS 8.1 interface to accomplish these goals. This exercise can be found on the class website. ArcGIS 8.1 consists of three components: ArcCatalog, ArcMap and ArcToolbox. ArcCatalog is used for browsing for maps and spatial data, exploring spatial data, viewing and creating metadata, and managing spatial data. ArcMap is used for visualizing spatial data, performing spatial analysis, and creating maps to show the results of your work. ArcToolbox is an interface for accessing the coverage processing and analysis function that come with ArcInfo 8.1. Also, it contains a large number of geoprocessing functions.
This exercise introduces you to ArcMap and ArcCatalog. You use these applications to create a map of pan evaporation stations in Texas, and to draw a graph of monthly pan evaporation data measured at these stations. The relationship between ArcGIS and MS Word and Excel is demonstrated so that you can create graphs in Excel, maps in ArcGIS and place the result in a Word file as a report for this homework. You use ArcCatalog to create a new personal geodatabase and import shapefiles and a coverage to a feature dataset, and thus you’ll have experience with all the vector data formats used in ArcGIS by the end of this exercise.
To carry out this exercise, you need to have a computer, which runs ArcGIS 8.1.
You will be working with the following spatial datasets during this exercise:
These shapefiles consist of three files each (evap.dbf, evap.shp, evap.shx and counties.dbf, counties.shp, counties.shx). The coverage is packaged as two folders (texas and info). You can get them from this Winzip file: arc.zip, which you have to unzip using the Windows utility Winzip. For UT Austin students the files are located on the LRC NT network in the class directory class\maidment\giswr2001\ex1\. This directory can be found in the LRC using Windows Explorer at My Computer\My Network Places\Entire Network\Microsoft Windows Network\lrc\civil3\lrc\class. You need to establish a working account to do the exercise on. This can be in c:\temp or in the diskette or zip disk drive of the machine you are working on. If you don't yet have a regular NT Login account at the LRC, get a temporary guest login to do the exercise.
ArcGIS License Server
This exercise can be executed with any of the options within ArcGIS, namely ArcInfo, ArcEditor or ArcView. Each of these systems provides access to ArcMap and ArcCatalog, which are the ArcGIS interfaces used to do the work. When you invoke ArcMap or ArcCatalog, it is possible that you will get a message saying that all the licenses for ArcInfo are in use on the network, or that you aren’t licensed for this application. In that event, you need to switch to an application with available licenses. To do this, invoke the ArcGIS Desktop Administrator, and select another application. In the LRC, ArcView [Single Use] works best, but in another lab setting, the ArcView [floating] or ArcEditor [floating] could be the right choice, depending on license availability.
Please note that the following procedure is a general outline, which can be followed to complete this lesson. However, the user is encouraged to experiment with the program and be creative.
A coverage is set of point, lines, or polygons that represent geographic features. The features are related using topology meaning that there are spatial relationships between connecting or adjacent features. The attributes of the features are stored in separate INFO tables. Coverages are one of the original types of GIS data available.
A shapefile is a homogenous collection of simple features that do not contain topological information. The format was introduced with ArcView 2.0 to simplify the representation of spatial data. A shapefile includes geometric features and their attributes. The attributes are contained in a dBase table, which allows for the joining with a feature based on the attribute key.
Viewing Shapefiles and Coverages in ArcMap
Shapefiles and coverages can be added to ArcMap and displayed without going through ArcCatalog.
(1) Open ArcMap and select the A new empty map option.
(2) Use the (Add Data) button to add the exercise data for this exercise. Navigate to the folder, which contains the data, and select all three files at once by using the shift key. Click the Add button to import the images.
In ArcMap, a layer consists of a reference to a spatial dataset (such as a feature class, shapefile or coverage) and a definition of how to display it (legend colors, line thickness, etc.), and a map is a graphical representation of geographic information. The left panel in the ArcMap window is the Table of contents, and the right panel is the Display window. The Table of contents lists layers, and the Display window displays maps.
As you can see it is very simple to add shapefiles and coverages to ArcMap.
(3) Click off the check marks next to the file names in the left hand column. Reselect each file name individually to that you may view what features each file contains.
When you are done explore the possibilities of ArcMap, exit the program. You do not need to save since you will be coming back to ArcMap later in the exercise.
Preview Shapefiles and Coverages in ArcCatalog
(4) Open ArcCatalog
(5) On the left panel, search for the folder where the exercise data is located. Click on the plus sign next to the Texas coverage and you will see that this file contains four other files.
In ArcCatalog, you can toggle the right panel display between a file tree (Contents tab), a data view (Preview tab), and a metadata document (Metadata tab).
(6) Highlight the arc file under the texas coverage and click on the Preview tab in the right panel. First look at the Geography preview.
You can see the arc file represents the outline of Texas. The preview option allows one to display the feature class table as well, by selecting Table instead of geography at the bottom of the panel. Switch to the Table Preview at the bottom of screen you will notice that the table contains attributes called FNODE# and TNODE#. These attributes represent the topology of arcs allowing for conductivity.
Click on the remaining files under the texas coverage to preview them. The label file occurs with every coverage and must not be filled. The polygon file contains a polygon representation of Texas. Finally, the tic file contains points that represent the real world coordinates of the polygon.
(7) Preview the two remaining files. You will notice they appear as they do in ArcMap.
A geodatabase is a relational database that stores geographic information. In turn, a relational database is a collection of tables logically associated to each other by common key attributes. It is said that a geodatabase can store geographic information because, besides storing a number or a string in an attribute column, tables in a geodatabase can store a geometric object (i.e., polygon, line or point) with defined shape and location. A geodatabase consists of two files with extensions mdb and ldb. Tables in a geodatabase are called feature classes. Thus, a feature class is a collection of objects that have the same behavior and the same set of attributes.
A feature dataset is a collection of feature classes that share the same spatial reference. The spatial reference describes both the projection and spatial domain extent for a feature class in the geodatabase. Because the feature classes in a feature dataset share the same spatial reference, they can participate in topological relationships with each other such as in a geometric network. These topological relationships can also be stored in the feature dataset. Note that feature classes in a geodatabase can exist as stand-alone feature classes, without being part of any feature dataset.
A feature class is a collection of features with similar geometry. There are point, line, and polygon feature classes. Two types of feature classes exist: simple feature classes and topological feature classes. A simple feature class includes features that have no topological associations among them and features maybe edited independently of each other. Topological feature classes are bond as one integrated topological unit.
Create a new Geodatabase
(1) To create a new geodatabase first right click on the folder that contains the data for the exercise. Select New/Personal Geodatabase and a new geodatabase -- called New Personal Geodatabase.mdb and represented by an icon with the shape of a cylinder -- will be created,
and (2) overwrite the name of the geodatabase with Ex1Data (the geodatabase will keep its file extension mdb regardless of whether you included it in the name or not).
Adding Data to the Geodatabase
When first loading data into a geodatabase, it is important to think about the data and how they are related. As mentioned above, in geodatabases the data is placed in feature classes that are then organized into feature datasets. A geodatabase can have one or more feature datasets. Each feature dataset has a single reference frame, which includes the map projection and map extent. It is possible to define the reference frame after the creation of the feature dataset and before data is loaded. There is a simpler method to be certain that your entire data will be completely contained in a feature dataset. When you load data into a feature dataset, the first feature loaded dictates the reference frame of the dataset. Therefore, you simply load the shapefile or coverage, which covers the largest extent, and all your data will be in the correct reference frame.
To add data to the Ex1Data geodatabase within a feature dataset, in ArcCatalog: (3) right-click on the name or icon of Ex1Data, select Import/Coverage to Geodatabase wizard, browse for the coverage Texas and click on the polygon feature class to convert. Click Next to get to the destination screen.
(4) Select the Create a new output feature dataset radial button, call the new feature dataset Texas. The new feature class will be called texas_polygon by default. You may rename it if you like.
(5) Click Next, accept the default parameters and click Next, (6) click Finish and a Texas feature dataset with a texas_polygon feature class will be created.
(7) Converting a shapefile to a feature class is very similar to the process described above. Right-click on the name or icon of Ex1Data, select Import/Shapefile to Geodatabase wizard, browse for the shapefile Counties and click Open, Click Next to get the destination screen. Select the Choose an existing output feature dataset radial button, call the existing feature dataset Texas, and name the new feature class counties,
and click Next, accept the default parameters and click Next, (8) click Finish and Counties will be added to the Texas feature dataset.
(9) Repeat the process for the shapefile Evap, but in this case name the new feature class Evap, and click Next. The shapefiles Counties and Evap have been added to the Texas feature dataset as feature classes.
After creating the geodatabase, the feature dataset and the feature classes, the ArcCatalog tree looks like this:
Note that the feature classes texas_polygon, Counties, and Evap could have been created outside the feature dataset Texas, but since they share the same spatial reference, it was decided to group them together within the feature dataset. Trying to import spatial data to an existing feature dataset may cause a conflict between different spatial reference frames. This is very likely to occur when attempting to import data to an empty feature dataset created without defining its spatial reference.
We will now add the feature dataset that we created in ArcCatalog to an ArcMap document. To display the spatial data of the Texas feature dataset in a map, first open ArcMap.
(1) You can launch ArcMap from within ArcCatalog:
or you can open ArcMap from the Start menu as you did before. Click on the Add Data button, .
(2) Browse to the feature dataset Texas, and click Add. This has the effect of adding all the feature classes in the feature dataset to the ArcMap display. You can add individual feature classes within the Texas feature dataset if you so desire, by clicking on the feature dataset icon, and then on the icons of one or more of the feature classes (Hold down Ctrl or Shift to select more than one feature class).
Note that the Table of contents lists the layers corresponding to the three feature classes of the Texas feature dataset that you just added, while the Display window displays the map with the corresponding spatial data (i.e., Texas counties and evaporation stations).
(3) Save your work in ArcMap by choosing File/Save and, after navigating to your working directory, writing the file name Ex1 (the file will be assigned the extension mxd).
(4) To change the appearance of a map display, you can access the Symbology menu just by double clicking on the Symbol displayed in the ArcMap Layer Table of Contents.
Click on the symbol color box, make your selections for the Fill Color and the Outline Color, and click OK, twice. Follow this procedure to modify the display of the Evap layer. Hopefully, the new map looks better than the original one.
More complicated symbol shading that has the color and size of the symbols varying according to attributes of a feature class, can be manipulated by accessing the Symbology tab of the Properties of the Feature Class.
Numerical and text information stored in the fields of the geodatabase tables are called attributes. To access attribute data of the feature classes at a specific location, in ArcMap: make visible the layers Evap and Counties (assuming you want to retrieve information of both layers) by clicking on Evap and then holding down the shift key select the Counties file. Make sure that the Texas layer is clicked off, or you’ll get information about this too.
(1) Click on the Identify Features tool:
(2) Click on the location on the map you are interested in, and in the Identify Results window, select the object you are interested in. In the figure, attribute data for the Austin Airport evaporation station and Travis County has been retrieved
If you inadvertently close the Tools menu you just used, you can open it again from the View menu:
Viewing an Attribute Table
(3) To access attribute data of an entire layer, in ArcMap: right click on the Evap layer name in the table of contents, and select Open Attribute Table:
Tables that contain attribute data of a layer are always called Attributes of <layer name>, and contain a field called Shape. The field Shape displays the words Point, Line or Polygon, but it really stores a geometric object with the shape of a point, line or polygon.
Note that record number 44 (indicated by the arrow in the table) corresponds to Austin evaporation station. All attribute data is the same as retrieved before, except for the Shape field, but that does not mean that the table stores information different from what can be retrieved with the Identify Features tool. You can see from the blue dot on the map, the geographic location of the Austin Airport where these pan evaporation data were measured. (4) To Clear a Selected feature and select a new one, use: Selection/Clear Selected Features in the ArcMap toolbar:
Selecting objects of a geodatabase table refers to tag a subset of the objects of the geodatabase table for a specific purpose. Object selection can be made from a map by identifying the geometric shape, or from an attribute table by identifying the record. Regardless of how you select an object, both the shape in the map and the record in the attribute table will be selected.
(1) To select an object from the map, in ArcMap: in the table of contents, click on the layer name Counties, click on the Select Features tool, in the display window,
(2) Click on the Counties polygons you want to select. To select more than one object, press the Shift key and hold it down while you click on the additional objects. Selected objects are displayed with a light blue outline, although the color might change depending on your settings. The corresponding attribute table records have also been selected. You can verify this by opening the Counties attribute table.
(3) To clear your selection, right click on the layer name, and choose Selection/Clear Selected Features.
(4) To select an object from the attribute table, in ArcMap: (a) in the table of contents, click on the layer name Counties, (b) select Open Attribute Table, (c) in the Attribute Table, click on the square at the left of the records you want to select. To select more than one record, press the Ctrl key and hold it down while you click on the additional records. Selected records are displayed with a light blue background, although the color might change depending on your settings. The corresponding objects in the map have also been selected. You can verify this by returning to the map window.
To clear your selection, click on the Options button of the attribute table window, and choose Clear Selection.
Charts are useful because they allow you to visualize trends in data. ArcMap has chart-making capabilities. We will plot a chart of one or more records selected from a geodatabase table. (1) First select the two evaporation points that are located in Travis County. To create a chart, choose Tools/Graphs/Create, this opens the Graph Wizard.
(2) You will be making a Column chart so just click on the Next button. The next screen will allow you to indicate the data to be used in the graph. The layer or table you will use is the evap layer. Keep the Use selected set of features or records selected. (3) Toggle the Fields button next to the phrase Graph data series using:. Now you will select the data to be graphed. We will make a graph comparing the evaporation at the stations selected for each month. (4) Choose the monthly values to graph by selected them. Click the Next button.
In the final step of the Graph Wizard you will specify the chart title and other presentation specifics. (5) Give the chart the title Pan Evaporation and label the legend with the attribute STAT_NAME. Play with the Bar gap to change the size of the bar.
Press Finish. You have created a graph in ArcMap!!
Making a Chart in Excel
Another option is to make a chart in Excel using the dBase tables given by the evaporation shapefile. Open the evaporation attributes table evap.dbf as a table in Excel. Use Files of Type: dBase files in Excel to focus only on .dbf tables when you open the table. Select the stations you want to plot, copy their records to a new worksheet, delete the columns you don't need there, and then create a chart. Here is an example chart created this way. The column headers have been renamed from Jan_Val to Jan, etc to make the Chart x-axis more attractive to view. The legend has been moved to the top of the chart to allow a wider spacing of the data in the chart.
To consolidate a map of counties of Texas with evaporation stations with the graph that you created before in a single sheet of paper, in ArcMap: (1) change the format of the display window from Data View to Layout View by clicking on View/Layout View,
Reduce the size of the data frame (i.e., rectangle where the spatial data is contained) -- to make room for the graph -- by clicking on the graph and moving its handlers. To insert the Chart, right-click on the chart and select Show on Layout. Move and resize the graph as necessary. You can draw lines to relate the location of the measurement stations and the data plotted on the graph using the Draw a Line tool at the bottom of the ArcMap toolbar. Or you can add text with the text tool shown next to the line draw tool. You can also insert a North Arrow by using the Insert menu in ArcMap.
Your final map could look like this:
You can print this map directly from ArcMap, or you can copy it into Word and print it from there. To copy a map into Word, Right Click on the map in the ArcMap Layout, and you'll see an option Copy Map to Clipboard. When you open Word, use the option Edit/Paste Special and you'll get a Window that allows for an ESRI ArcMap Document Object. If you hit OK here, then your map will paste right into Word as it looks in ArcMap!
Here's another option: suppose you want to take a chart in Excel and add a map to the Chart to show where the data apply. If you Copy the Map to the Clipboard in ArcMap, you can Paste it in Excel and annotation to connect the map to the Charted data:
The manipulations just described transfer objects from one application to another. A more general procedure is to simply copy the screen to the clipboard and cut out the part that you want, saving it to a file for later use. That is how all the images in this exercise were prepared. To copy any image, hit Shift/Print Screen on your keyboard (this copies the Screen onto the Clipboard). From the Start Menu in Windows, Open Accessories/Paint.
Use Edit/Paste to paste the contents of the Clipboard into Paint. You'll now see an image of all the things on your original computer screen. Click on the open box under Edit so that the cursor becomes a cross and use it to draw a dashed box around the portion of the image that you want to keep.
Use Edit/Copy To to save the file as a .bmp bitmap file. Then in Word, you can use Insert/Picture/From File to insert the .bmp file into Word. Note that in ArcMap you can use Insert/Picture to similarly insert pictures into your maps!! Very cool!
Now that you are familiar with the operation of ArcGIS 8.1, make some new maps in places that are of interest to you. Some additional data showing precipitation, temperature, and net radiation values for the whole world on a 0.5° mesh, can be found in Txclim.zip, or in the Climate folder in the same place in the LRC class folder from which the original data for this exercise were obtained.
To Be Turned In: A completed map and chart of selected data.
may be used for research and educational purposes only. Please credit the
authors and the
Center for Research in Water Resources at The University of Texas at Austin.
All commercial rights reserved. Copyright 2001 Center for Research in Water Resources.