Fig. 1. ArcMap's Starting
Window
This hands-on GIS exercise is required of all incoming MCP students in the MIT Department of Urban Studies and Planning. It is intended to help you become familiar with the MIT computing environment, with common geoprocessing services and GIS software that the Department, MIT Information Services, and the MIT Libraries provide, and with a few specific tools for locating, downloading, and utilizing spatially referenced data. In this exercise, we will download data describing the geopgraphic boundaries of the 351 cities and towns within the State of Massachusetts and another zipped bundle of small datasets describing the geography, infrastructure, and demographics of Cambridge, MA. We will then use ArcGIS software (and ArcMap in particular) to develop a thematic map of median household income for Cambridge at the census block group level of aggregation (as of 2000). We will also add to our Cambridge map the locations of residential property sales from 1987-1989 and Cambridge roads. Finally, we will prepare a PDF-formatted map for submission onto our online website and learn to 'mash up' our thematic map on top of Google Earth for viewing in context from the Web.
The exercise is due at the end of the first week of Fall classes and all the preparation that you need for the exercise is covered during the one lecture during orientation week in Room 9-450 on Wednesday, Sept. 1, from 3:30 - 5 pm. You can find this exercise, the necessary datasets, and further information about lecture notes and optional lab times at the Stellar Website location for this Orientation Week GIS Introduction. http://stellar.mit.edu/S/project/gisintro/
First, we need to Log In to a PC (or Mac) that can run ArcGIS and access the relevant websites and data lockers. We will use WinAthena PCs and/or dual-bootable Macs that can be booted into Windows XP or Windows-7 such as those in various MIT teaching labs - e.g., Room 37-312 or the CRON facilities in buildings 9 and 10. The user name and password that you will use to log in are the same as for your MIT email.
Step 2. Find the lab exercise instructions on the class website
Launch any web browser on your PC's desktop (either Mozila Firefox or Internet Explorer will do) and find this GIS Intro lab exercise on the Stellar website: http://stellar.mit.edu/S/project/gisintro/ Navigate to the webpage for this exercise keep it open in a web browser while you work. You may print a copy of this exercise if you wish, but we recommend working directly from a browser window. If you are working in the lab of Building 37, the second monitor can be used to display the lab instructions. To do that, grab the browser titlebar with a 'left-click and hold' on your mouse and drag it onto the empty right-hand screen.
Step 3. Understand enough about web browsing and the basics of local and network file storage at MIT to be able to find and download the required data
Many GIS datasets that are of interest to urban planners are public and freely available from various online data repositories, or semi-private and accessible via passwords or Web certificates from protected websites. However, most of these GIS datasets are large - far too large to store copies on every machine or even to download entire datasets from online sources. In addition, sharing network file storage across various MIT machines may be more complicated thant you are used to because of the complexity of MIT machines, software, and security measures, and the fact that many GIS datasets involve bundles of files that must be kept together.
Here are some of the places where you may want to access and store GIS datasets and your various work products:
For this exercise, we will (a) examine and download the boundary files for Mass cities and towns from the MIT Libraries GeoWeb server, (b) download a zipped bundle of small Cambridge files from the Stellar website, (c) use ArcMap to prepare our thematic map, (d) save our map as a KMZ-formatted file in our MIT (Athena) locker for viewing with Google Earth, and (e) upload a PDF-formatted version of our map as part of the homework assignment that we upload to the Stellar website. Since we have several days to finish the exercise and a full orientation schedule, we will probably not do the exercise all at once. Hence, we will need to be clear about how to save various pieces of our work so that we can pick up where we left at later times and on different machines. You will need to understand enough about the MIT setup for handling files on Windows XP and/or Windows-7 machines to find various virtual lockers and know which ones are physically located on your local macihne. Some of this information was already covered in Tuesday's general introduction to MIT's computing facilities. Some additional tricks and traps regarding saving and reusing files and work-in-progress are mentioned later in this exercise and will require some special attention.
For now, we suggest that you open a window that lets you examine the local and virtual file system that is accessible to your local machine. On Windows-XP machines, this application is called 'Windows Explorer' (not to be confused with the browser called, 'Internet Explorer'). You can start a 'windows explorer' window by double-clicking on the local computer icon on your desktop, or running the 'explorer.exe' program. On Windows-7 machines, you can click on the 'folder' icon in the bottom 'tray'. Use this windows explorer 'shell' to navigate through the icons and directory trees to get a sense of how your machine is configured by reading the names of the folders (i.e., sub-directories) where files and resources are stored. Beware that, on MIT's WinAthena computers, most of the places called 'Documents,' 'Desktop,' and indeed most of C:\Documents and Settings\... are *not* physically located on the local machine. They are actually shortcuts to network lockers (on your 'H' drive) that can be accessed from any WinAthena machine. Other locations - those including the string '\afs\' in their name - are part of a so-called Andrew File System that can be accessed by any machine running OpenAFS software. Your local machine treats these AFS lockers as if they were located on drive "I" (for your personal locker) or drive 'Z' (for the \\afs\all top level of all the AFS lockers).
All the network lockers are convenient because they move with you from machine to machine, but using them for GIS data processing can be slow and is risky since any network hiccups could cause you to corrupt your data or freeze ArcMap in its tracks. The truly local disk drives are fast and more reliable, but you have to remember to copy things to the network (or a thumb drive) before you finish a session - and copying collections of GIS datasets can be time consuming and prone to errors. For this exercise, the datasets are small enough that their location does not really matter, but for serious GIS work (such as for a class project or thesis), paying attention to where your data are saved can save you considerable time and agony.
Step 4. Use the GIS software (ArcMap and ArcCatalog) to prepare your thematic map showing household income patterns across Cambridge together with the location and sale price of Cambridge residences. If you haven't already started the ArcMap application, do so via the following steps:
1. Click the Start button (or Windows-7 symbol) on the lower-left corner of the display
2. Move the mouse over the item Programs.
3. Move the mouse over the item ArcGIS
4. Move the mouse over the item ArcMap and Click.
Please wait patiently for ArcMap to launch. The program takes awhile to come up. Notice that within the program group for ArcGIS, there is another entry called ArcCatalog, which we will use shortly.
When ArcMap first launches, you should see an "ArcMap" window, illustrated in Fig. 1, that prompts you to create or open a new map. Click the radio button next to A new empty map and then 'OK' to make this window go away.
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| Fig. 1. ArcMap's Starting
Window |
You should now be looking at an "empty" document which has "Untitled" in the title bar that looks like the image in Fig. 2.
 |
| Fig. 2. The Untitled map document
|
The above graphic shows approximately what ArcMap might look like. All of the controls are dockable.
That is, the tools panel, which has the pan and zoom tools, is free floating.
But you can drag and drop it onto the top tool bars, if you wish. ArcMap saves a configuration file in your personal network locker so that it can remember your setup from one ArcMap session to the next. Wihle that is often helpful, it means that every veteran ArcMap user may have a slightly different setup to the above graphic may look a little different on your machine. In general, the ArcMap user interface will have, in addition to the pan and zoom tools just mentioned, some drawing tools
(see the bottom of the window), some menus which give you access to customizing
tools among other things, and some map management tools. We will use a few of these before we finish this exercise.
Step 4: Save your work and upload your homework assignment. After you have used ArcMap to prepare your thematic map of Cambridge, you will need to produce a PDF-formatted version of the map to upload into Stellar, and a KMZ-formatted version of the map that can be overlaid onto Google Earth. You will also want to save your datasets and working files in case you need them again. The workspaces on the local machine are erased periodically and cannot be accessed from a different machine, so you will need to move your work to a thumb drive or your network locker. For the KMZ file to be visible on the Web, it needs to be located in web-accessible locker. (For example, the ' www' sub-directory of your network locker can be seen on the Web via the address: http://mit.edu/your-athena-name/www).
Now that we have a general idea of what we are trying to accomplish and have taken a first look at some of the tools we will use, let's find the data that we will need and move a copy into a location and form that can be accessed from within ArcMap.
We will use the public version of the MIT GeoWeb services to find, examine, and download the Massachusetts town boundaries.
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Fig. 3. MIT GeoWeb Homepage |
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Fig. 4. MIT GeoWeb with Boston MBTA Subway Lines Selected and Ready for Download |
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Fig. 5. MIT GeoWeb with 'Mass Towns' Layer Added to the Map |
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Fig. 6. MIT GeoWeb Ready to Download the Mass Towns Layer |
We are now ready to begin looking at data sets through the lens of the ArcMap software. We hope you will not get bogged down with file system navigation and downloading details so that you are able to spend most of your time using ArcMap to analyze, visualize, and symbolize your data sets.
Find and re-open the window that opened when you started ArcMap in Step 4 of Part I above. When a data set such as a 'shapefile' is brought into a map document, we will call it a layer. We need a new term because the same data set can be used to build many different layers, depending on the symbology used and other variables.
We can add data sets to this map by clicking on the "Add Data" button 
in the toolbar to open the navigation tool shown in Figure 7. Try this now. We want to add the Mass Towns boundaries and the three Cambridge
shapefiles that we downloaded in the previous section.
 |
| Fig. 7. Add Data |
Note that the dialog box for adding data begins with Catalog. Local drives
such as C and D are registered with Catalog by default. If you have saved the shapefiles on a network drive or thumb drive, you will need to register
those drives manually using the "Connect to Folder" Button 
.
Navigate to the folder where you saved the four shapefiles - e.g., C:\USERTEMP\your-athena-userid and select all four shapefiles. (You can hold down the 'shift' or 'control' key to select more than one file in the navigation window.)
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| Fig. 8. Adding Cambridge border coverage via drive Z: |
After adding all four shapefile, you should end up with a map window looking simlar to Figure 9.
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| Fig. 9. ArcMap window with GIS layers |
These four layers are currently visible. To activate a layer or deactivate it, just click on the box next to that layer's title. If the box is checked it means that the layer is visible. Initially, all the checkboxes are checked, and all data will be visible in the data display area. Experiment with turning layers on and off.
Notice that some layers may obscure others. That's because the themes are drawn from bottom to top as listed in the data frame area. You can change the drawing order of the layers by clicking and dragging a layer in the data frame area. Try this now to see how the display changes while you arrange the layers in different ways. But finally, they should appear in the following order: (Note that, for the rearrangement of layer order to work, the active tab at the bottom of the left-side window listing the "Layers" must be "display" and not "source" or "selection".)
Your window should now resemble the above figure. Note that since ArcMap chooses the initial colors for themes randomly, your window will probably have different colors than those shown here. Also, the name of the layers may also be a bit different, depends on whether you use a coverage or a shape file.
At this point it is important to set a few properties for this document file. Select Data Frame Properties under the View menu. The "data frame properties" window will show up. Click "general". The window looks like the Figure 10.
 |
| Fig. 10. Data Frame Property
Window |
Now change the name of the view from layers to Lab Exercise 1. Also notice that in this dialog box the map units are set to meters, in which the spatial coordinates of the data are actually stored in the files on the disk. The display units, in contrast, refer only to how distances will be measured for display. We can set this to any units we like; we suggest feet here because that is a familiar unit (for Americans) and is appropriate to the scale of the map.
Now take a few minutes to familiarize yourself with some toolbar buttons. You can pan and zoom in the view window. First, you may wish to enlarge both the ArcMap window and the data display area so that you can see more detail in the image. Also try these buttons out by clicking on them in the toolbar, then clicking in the data display area:
| Zoom In |  |
Click to zoom in on that location. Click and drag to zoom to a particular bounding box. |
| Zoom Out |  |
Click to zoom out centered on the location of the click. |
| Pan |  |
Click and drag to pan around the map area. |
Discover functions of the other buttons on the toolbar on your own. Notice that as you move your mouse cursor over the button, a line of descriptive text will appear, which explains the function of the button.
Click on the small boxes next to the each layer to make them invisible. Then turn on the layer Cambbgrp in the data frame. Now you can see the outlines of Cambridge Census block groups.
Click once on the info ("i") tool 
.
This button is located in the toolbar. Move the mouse into the map window and
click on a block group. The attributes associated with that block group appear
in a popup window. To see the data for all of the block groups, move your mouse
over the name of the layer in the data frame and do a right click. On the pop-up
menu, choose "open attribute table". Notice that if you click on a
record in the table, the corresponding block group is highlighted on the map.
Before we spend too much time analyzing and mapping our data, we should save a so-called 'map document' that allows us exit ArcMap, then restart it and pick up where we left off. Sooner or later, your ArcMap session will hang or crash and you will regret not have saved your ArcMap document sooner! To save your ArcMap session into a retrievable file (with an MXD extension), click
the save button 
. in the toolbar area or File/Save-As from the menus. You could save the document to your Athena
locker, which is your I: drive on the WinAthena computers. That way, the document will be accessible from any WinAthena machine. We suggest you create a sub-directory
called gisintro within your I:\Private
directory. Within this directory, you should create another folder called lab1.
Now you can save your map document file to this directory. Give this document
file whatever name you like. It does not save all the data you are using - only
the file locations, date frame properties, symbol information and the like that
are needed for ArcMAP to recreate the same state of your work that existed when
you saved the file. (Hence, the saved document file - with an .mxd
filename extension - will not work properly if the shapefiles used by ArcMap are not located in the same folder as when the ArcMap document was created - that is C:\USERTEMP. If you reopen a saved document file and the layers are greyed out in the table of contents with an exclamation point next to them, it means ArcMap cannot find the data. Right click the layer name and choose Data/Repair-data-source to navigate to the directory containing the shapefile.)
Click on the check box next to the Cambtigr layer to make it visible. You should see all Cambridge roads (plus some other features such as railroads) being drawn on the map. If you had moved, say, Cambgrp above Cambtigr in the legend, the TIGER(Topologically Integrated Geographic Encoding and Referencing system) arcs would then be quickly covered up by the block groups. If so, you can fix this by dragging the Cambtigr layer up above the Cambbgrp layer. Now we see TIGER arcs on top of the block groups.
The name Cambtigr may not be meaningful to everyone viewing this display. We can easily rename the layer in the property window to something more readable. Right click once on the word Cambtigr and select Properties from the pop up menu. Under "General", change the layer name from Cambtigr to Cambridge TIGER. Notice that the data source (listed in the legend when the "Source" tab at the bottom of the DataFrames 'legend' window is selected) does not change. After you click the OK button, you will see the new layer name in the data frame. You may need to need to make the data frame window wider to see all the text. Move the mouse over the line to the right of the data frame area. When the cursor changes to an I-beam with arrows on either side, you can click and drag to resize the data frame area.
For now, the Mass Towns layer is listed in the table of contents with a long and cryptic name (such as 1283219223_US_MA_BOSTON_P33MBTA_2006). Right-click the name, choose properties, and click the 'General' tab. Change the long name to something like 'MassTowns' and click 'Okay.' If this layer is obscuring the other layers, you can drag it down below the others in the table of contents. (Note that reordering the layers in this manner only works when the "display" and not the "source" tab is active. at the bottom of the 'table of contents' panel.) However, when MassTowns is on top, it obscures the roads. Instead of moving MassTowns to the bottom, we can change the way it is displayed so that the border is drawn but the area is not filled in. Double-click on the legend, which is the rectangle under the layer name MassTowns in the Symbol Selector window as shown by Fig. 11. Click once on the downward arrow of the "Fill Color" option, which is at the middle right. And then choose "No Color". This sets the fill color for the shape to be "none" (i.e., transparent). The fill pattern had been the colored box, meaning that shapes should be filled with a solid color.
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Fig. 11. Symbol Selector Window |
Also, increase the outline width from 0.40 to 2. Click "OK". Now you are able to see, at the same time, the boundary of the Mass Towns and the block group boundaries within Cambridge. Likewise, you can improve the way to visualize the tiger street centerlines. Try that on your own.
Double-click on Cambbgrp to open the layer property window. This time we will manually symbolize the theme. Up to now, all the layers have used the default legend type, "Single Symbol." Now, under "Symbology," select "Quantities" and then "Graduated Color." Change the classification field value to "Med_hh_inc." Notice that ArcMap automatically divides the income data into five ranges and assigns a color to each. These colors will not actually be shown in the map until we explicitly tell ArcMap to do so.
|
|
| Fig. 12. Symbology
Window |
Often we will want to make some adjustments to the way these ranges are created. To do so, click on the Classify button. The Classification window will appear as shown in Figure 13. Under "Classification Method:" select "Quantile" and note breakpoints are adjusted for the histogram along the bottom of the classification window. Click OK to close this window.
|
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| Fig. 13. Classification
Window |
Back in the symbology window notice that the ranges have changed to reflect
the new classification scheme. Now click Apply to make this new
scheme take effect in the map. You've made your first thematic map, with median
household income divided into 5 categories, each consisting of 20% of the block
groups. If some boundaries of some block groups are highlighted, select the
feature selection tool 
,
and then click on the blank map area.
Notice that the first income range is 0 - 23472. On the surface, this may seem fine, but actually in this data set, the value zero is used to indicate that there is no data for that block group, not that the median income is zero (which is extremely unlikely). You can confirm that the zero value is an outlier by taking a quick look at the raw data. Close the property window and bring forward the attribute table of Cambbrp. Right click the layer's name in the data frame and select Open Attribute Table on the pop-up menu.
Scroll to the right in this window until you see the Med_hh_inc
column. Right click on the column heading for Med_hh_inc; it
will be highlighted video when you do so. Now sort the rows in ascending
order using the Sort Ascending option 
.
You should end up with a window that resembles Fig. 14. Notice that there are
three blockgroups with zero values, and the next higher value is 13009.
 |
| Fig. 14. Sorted
Attributes of Cambbgrp |
We can prevent such situations from distorting our maps by specifying a "null value" in the classification. Go back to the classification window and click on the Exclusion button. The Data Exclusion Properties window will appear.
Specify the query to match what is shown in Fig. 15. And then go to the Legend Tab. Type in "Null Value" in the label field. Make sure the check box for Show Symbol for Excluded Data is checked. Click OK. to close the window. Notice that all but the last of the ranges changed; in particular, the first range is now 13009 - 25335.
 |
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| Fig. 15. Exclude Non Value Records | |
Now we can experiment with different classification methods. Try going back to the symbology window, then click the "classify" button and classify Med_hh_inc by "Standard Deviation" instead of "Quantile." The mean should match the mean generated under statistics. In fact, once you become a proficient map maker, you might not use these preset classification schemes at all. You could type your own ranges into the "Value" field of the Legend Editor, basing your ranges on standard deviation, variance, quartiles, quintiles, or any other defensible scheme you devise.
What are these different classification methods about? Now is good time to use the ArcGIS online help system to get some more information. Select ArcGIS desktop help from the Help menu. (The same Help system is directly available from the windows Start/Program/ArcGIS menu.) The help system may take some time to load. In the ArcGIS Desktop Help window, click on the "Index" tab. In the keyword box, type the first few letters of the word you're looking for, i.e. classification. You will find "classification schemes" in the returned query list. Click "display", then select "Standard classification scheme" in the pop up window, explanation for the classification method will show up in the right area.
More thematic mapping
Now let's go back to the ArcMap window. Right click once on the Cambbgrp layer and select Copy from the pop up menu. Right click on the data frame name Lab Exercise 1, select Paste Layer from the pop up menu. Now you will have two identical Cambbgrp layers in your data view. Rename the new layer from Cambbgrp to Households. You can do this as by bringing up the layer property window, as indicated in the previous section. However, you can also do it by clicking the layer name twice, as you would change a file name in a windows explorer. (notice that it is not a double-click.)
Now let's make a basic thematic map showing the number of households per block group. Double-click on the new layer named Households to load the symbology window. Under "Symbology" select "Graduated Color". Change the classification field from Med_hh_inc to Households. Click on the Classify button to open the Classification window. Use these options:
Type: Quantile
Number of classes: 5
Right click once on the Households layer and select Copy from the pop up menu. Right click on the data frame name lab exercise 1 and Select Paste layer from the pop up menu. Now we have three versions of the block groups visible in the legend. Change the name of newest one from Households to Household Density. Double-click on the new layer to load its property window. Change the normalization field from NONE to Landacre. Remember to go to the classification window and change the classification method to Quantile. The default one is Natural Breaks.
Instead of showing raw counts of households per block group, the Household Density layer shows households per acre in each block group. The density layer normalizes the raw counts by dividing them by the land area. Note that a density map is more meaningful than a map of block-group counts since the counts are so sensitive to where you draw the block group boundaries. If some block groups were divided in two, the thematic map of counts in each block group would change a lot, but the density wouldn't change. Use the checkboxes to toggle the visibility of the layers. Notice how different the two maps look and understand that household density is quite different from total households. Also understand what the normalize command did. It took the number of households in the block group and divided it by the number of acres in the block group. Normalization of data is an important issue that we will return to during the semester.
Make a new copy of the household density layer and change its name to Household Density SD. Load its symbology window with a double-click on the layer name. Make sure your classification field is "Households" and that you are normalizing by "Landacre." Click on the "Classify..." button and choose "Standard Deviation" (accept the defaults for the other fields). Apply your changes. This map helps us see how much density differs across the city. We see mainly light colors (within +/- 1.5 standard deviation from the mean), leading us to believe that Cambridge households are relatively evenly spread around the city. This makes sense because there are no (or few) 40-story high density apartment buildings, few areas with single-family homes on large lots, and few completely nonresidential districts.
Mapping point data
So far we've only looked at polygon data. Mapping point data offers new challenges and opportunities. Make the layer sales89 visible. We see that property sales were pretty evenly spread across the city in 1989 (except in a few block groups, most notably around MIT). Simply looking at where sales were isn't very interesting in this case.
Load the symbology window with a double-click. Choose the "Graduated Symbol" legend type and classify on "Realprice" and classify by "Quantile." Apply your changes. This gives us an idea of where the high-priced sales were. Go back into the symbology window and experiment with manually changing the colors and sizes of the dots. Also make a copy of the theme and try mapping the data using "Graduated Color" instead of "Graduated Symbol." Which method do you think is better?
Configure your data display window to show Income shaded thematically, Cambridge TIGER, sales89, and MassTowns. Turn off all other layers. Now you are ready to make a map. Under the View menu select Layout View. You get a default map layout in the data display area. We've worked with data layers in the data view, and now we are working with a layout document. Although we can print a map directly (using the Print command under the File menu), it is impossible to control exactly how it will look on the page without using a layout. Besides the GIS layers, a layout usually also includes a title, legend, scale bar and north arrow. These are the most basic components of a map.
This default map layout has no title, scale bar or legend. You can either insert these components one by one or apply a template. Let's first apply a template. Click the last button on the right side of the layout tool bar (see Figure 16), which is "change layout".
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| Fig. 16. Layout
Tool bar |
From the 'select template' window (see Fig. 17), select "LetterLandscape.mxt" under General tab and click "finish" button.
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| Fig. 17. Applying a map Template |
This template adds a Legend, North Arrow and Scale Bar to the map layout. But the map title is still empty and your layout window may look something like the messy one in Figure 18.
|
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| Fig. 18. Map Layout After Applying a Template |
To add the title, double click on <Double click here to enter the title>. In the text box of the property window, type in GIS Intro Lab Exercise.
Additionally, we need to add a few more elements to the map:
Let's add the data source first. Click Text under the Insert menu. A small text box shows up in the middle of the map. Double click the text box to bring up the property window. In the Properties dialog box that comes up, type:
Sources:
U.S. Bureau of the Census, 1990
Banker and Tradesman Real Estate Transfer Database, 1987-1989
Note that you can use the <Enter> key to insert line breaks in the text. Once you click OK, the text is placed wherever you clicked in the layout window. You can move this text by dragging it with the mouse. You can double click on the text, bring up the property window and change the font and size until you are satisfied.
In the same way, we can add two subtitles. Underneath the title Lab Exercise 1 add two subtitles in smaller text that read "Median Household Income in Cambridge, MA in 1990" and "Housing Sales in Cambridge, MA in 1989." Also add your name and today's date somewhere on the map.
Feel free to move and resize the elements to make your map look more attractive. You can also go back to the symbology window to adjust the existing symbology. Once you change the symbology, the change will be applied to the map layout automatically. You don't need to create the layout again. Try your best to make the map readable and attractive. Although it is hard to make a real attractive one this time, we expect your map should be much better than Fig. 16.
Before you print out the map, make sure that none of the visible features in your map are selected -- these will show up highlighted in yellow on the map. If they are, they will also show up highlighted on your printout, which you probably don't want.
If you want to print out your map, you can now do so with confidence. However, to save a few trees and avoid some of the hassle, you will not need a hard copy and will instead generate a PDF file and upload it to Stellar. To produce a PDF-formatted file containing your map, be sure to have the View set to 'layout' in ArcMap and Choose File/export-map. Set the 'save as type' to PDF, navigate to the directory where you wish to save your PDF file, edit the name of your file, and click 'Save.'
When printing directly to a printer, make sure to select the correct printer. Common choices include:
Select Print from the File menu. Click Setup button and select the name of the printer in the room where you are doing the lab (see "Printing Notes" below) and click the OK button. Make sure your printout actually shows up! Getting acceptable paper output isn't always as easy as you'd think. You can't be sure it will work until you have the piece of paper in your hands. When saving your maps to a file for later printing or use in a graphics or paint package, click on the "Print to File" option to save the file to disk in EPS format for printing or export later. Make sure this filename ends with .eps or .ps.
Remember to save your work again by clicking the disk icon or choosing File/Save.. ArcGIS can save the status of your session in the map document file, which typically has an .mxd extension. The map document file does not contain the data sets itself, but rather stores pointers to their locations. Your thematic map properties and layouts are also stored in the document file. After you have done additional work on a map document that you previously saved, you may want to save your changes under a different name by using Save As instead. Try this now, saving a copy of your map document as lab_1copy.mxd. Saving variations of your map documents under different filenames is a good practice. The map document files themselves are typically not too large, so making lots of map document files should not waste too much disk space and provides some recovery help if your working document gets corrupted.
We have already discussed how to save your ArcMap document as an MXD file. However, this document file does not include all your data. Instead, it just saves the name of the local drive and folder in which you have stored all the shapefiles. To improve performance and reliability, we suggested that you save your downloaded shapefiles in C:\USERTEMP\your-athena-userid. However, this folder is only usable on the local machine and it is erased periodically whenever the local drive gets too full or the machine is rebooted. You will need to copy all these shapefiles from the local drive to a network locker or a thumb drive before you logout. Since we have four shapefiles and each one consists of between 4 and 7 separate files, the easiest way to move the data is to store all your shapefile in a single folder (or sub-directory) and then copy and paste the entire folder from, say, C:\USERTEMP\your-athena-userid\data to I:\Private\gisintro\data . You may also use the ArcCatalog tool to copy or move shapefiles (and other more complicated ESRI geospatial datasets) across local and network drives.
When you login again and reuse your saved document file - with an .mxd filename extension - keep in mind that it will not work properly if the shapefiles used by ArcMap are not located in the same folder as when the ArcMap document was created - that is C:\USERTEMP\your-athena-userid. If you reopen a saved document file and the layers are greyed out in the table of contents and have an exclamation point next to them, it means ArcMap cannot find the data. Right click the layer name and choose Data/Repair-data-source to navigate to the directory containing the shapefile. For this exercise, the shapefiles are small enough that you can use them directly from network drives without much of a performance or reliability hit. But, with bigger shapefiles, it is an invitation to slow processing and sudden software crashes.
Let's see what it takes to overlay the map file onto Google Earth. The ArcGIS Toolbox provides conversion tools that allow you to write out an ArcMap layer or ArcMap document in a format that can be read by Google Earth, Google Maps, and other map viewing applications that adhere to the 'KML' protocol for representing mapable 3D data. (KML stands for Keyhole Markup Language. Keyhole was the company that originally developed what became Google Earth. KMZ is the compiled version of KML.)
In ArcMap, open the ArcToolbox pane, click the 'Search' tab, and search for 'kml'. Double click on the 'map to KML (conversion)' choice and a 'Map to KML' dialog box with open up as shown in Fig. 19.
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Fig. 19. Convert ArcMap file to KML |
Set the Map Document to be lab_1copy.mxd (in what ever directory you have saved it) and set the Data Frame name to be whatever Label is shown for the Data Frame in ArcMap (if you never renamed the data frame, it will be called "Layers"). Finally, set the output to be lab.kmz within a writeable directory. Set the 'layer output scale' to be '1' so the layer is always turned on. (Before you click on 'map to KML' you can click the 'locate' button to see where this tool fits within the ArcToolbox hierarchy.) Finally, open Google Earth and click File/Open to navigate to whereever you saved lab.kmz and open the file. If you saved the KMZ file to a web-readable directory such as the 'www' sub-directory of your Athena locker, then you could also open lab.kmz in Google Earth via 'Add/Network-link' using this URL: http://mit.edu/your-athena-id/www/lab.kmz
Finally, save and turn in a screen shot of the Google Earth screen once you have zoomed in to the Cambridge area and can see the your thematic map. an example is shown in Fig. 20.
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| Fig. 20. Overlap your map on Google Earth |
If you finish the lab assignment with time to spare, you may want to return to ArcMap and experiment with the other map styles and symbolization. You should also experiment with saving ArcMap documents, existing ArcMap, moving the shapefiles, and then restarting ArcMap and resetting the data source from the data layers to be sure you understand where the data are stored and how ArcMap references them. and various styles of the map components. Also, you can change the default setting so that ArcMap saves filenames with relative rather than absolute pathnames. Check out File/document-properties to experiment with the choices.
Finally, be sure to check out the ArcGIS online help (started from the Help menu). The online help is quite extensive and useful once you get some of the basic vocabulary down. Just be aware that, on WinAthena computers, the javascripts sometimes generate false error messages when you try to open the help files or ArcToolbox from within ArcMap . If you encounter these error messages, just click either 'yes' or 'no' to get through the several messages until the help windows or ArcToolbox pane opens up. If worse comes to worse, you can open the ArcGIS help files and ArcToolbox application directly from the Start/Programs/ArcGIS options.
Turn in to your PDF-formatted map (from Part V) and the screen shot of your Google Earth overlay (in Part VII) into the Stellar website for this GIS exercise: The lab assignment should be uploaded to Stellar by 8 pm on Monday, Sept. 13, 2010.
Originally created by Raj Singh for use in 11.520 and 11.188.
Modified for Fall 2001-2010 by Thomas
H. Grayson, Joseph Ferreira, Jeeseong,
Jinhua Zhao, Xiongjiu Liao, Mi Diao, Yang Chen, Zhu Yi, Lulu Xue, and Shan Jiang.
Last Modfied for Fall 2010 by Lisa Sweeney and Joseph Ferreira.
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