| 11.188: Urban Planning and Social Science Laboratory |
[Click here for today's in-class notes. ]
In this exercise, you will build on the basic ArcMap techniques you explored in Lab 1 to make more sophisticated thematic maps. In the exploratory map section, you will compare two thematic maps of the Cambridge population. One map shows population counts by block group and the other normalizes the population counts by dividing by land area to show population density. In the explanatory section, you examine the spatial pattern of home sales prices to see if they appear to be related to housing density and then spend some time considering appropriate symbology and data classification for visualizing the relationship. Once again, you will output some of your maps in PDF format for submission onto Stellar.
Accessing the class data locker.
Most of our class data resides in the 'data' sub-directory of our course locker. This locker is accessible via the Andrew File System (AFS) as Z:\course\11\11.188. (The 'worldwide' location of the class locker within the Andrew File System is: "\\afs\athena.mit.edu\course\11\11.188\" and most WinAthena machines at MIT map the Z:\ drive to athena.mit.edu which is the top of the Andrew File System on the MIT network.)
Attaching network lockers:
Since we will use the class locker repeatedly, we might as well map the class locker to a 'virtual' local drive and avoid having to navigate from the top of Z:\ each time. In the table of contents for Windows Explorer, right-click on the icon for your local machine (either 'Computer' or 'MyPC' or something similar). Choose 'Map Network Drive...'. (Prior to Windows 7, you would use the Tool/Map-network-drive option from a Windows Explorer window to map the class locker.) We suggest that you map the class locker using this name "\\afs\athena.mit.edu\course\11\11.188\" to your M:\ drive. Another way to map the class locker to a local drive is to run this command in a DOS command window: "net use M: \\afs\athena.mit.edu\course\11\11.188". This command has been saved as a batch command file named "attach_m.bat" at the top level of the class locker. You can navigate in a Windows Explorer window to Z:\course\11\11.188 and then double-click on attach_m.bat to mount the drive. You may also copy this batch file into a convenient location in your personal locker (on Drive I:) and double-click on it when you want to mount the class locker. Also, for most CRON machines, drive S:\ may be mapped to the top of the course lockers for all DUSP classes. In that case, S:\11.188 is handy as the top of our class locker.
The lesson from all this is not to remember the details of each method. Rather, it is to understand the basic idea behind hierarchical file directory trees and the notation that Windows and AFS use to navigate through them and to associate network lockers with local (virtual) disk drives.
Now that we have a general idea of what we are trying to accomplish, and have some idea from Lab #1 of the tools we will use, let's find the data that we will need and copy the datasets to a local drive in C:\temp. For this week's lab exercise, we will use several of the data layers from Lab #1 plus some new datasets. Although these shapefiles are fairly small, their use in ArcMap will be much faster if we download them to a local drive before adding them to ArcMap. You can use the Catalog tab in the ArcMap window to find and copy the data layers to a local drive before adding them to your ArcMap table of contents. (Remember, shapefiles consist of several separate files that begin with the same filename. When you copy a shapefile using ArcCatalog, it lists the shapefile only once but copies all the files. If you use Windows Explorer to copy the shapefile, you must be sure to copy every one of the files that begin with the shapefile name.)
For this lab we have already bundled the needed datasets into a single 'zip' file. To insure that you copy all of the needed files for Lab #2, we have bundled them into one 'zipped' file called cambridge_shapefiles.zip. This zip file is located in the data locker (M:\data) and contains shapefile versions of three data layers that we used earlier in Lab #1 plus a road layers and a new land use layer (plus a few symbology files that we will use later on).
cambbgrp - a shapefile of Cambridge 1990 us census
blockgroups
cambtigr - a shapefile version of the street centerlines
for Cambridge roads
landuse85 - a shapefile of Cambridge land use (from
MassGIS)
sales89 - a shapefile version of the point locations of
residential home sales in 1989
majmhda1 - a shapefile of street centerlines from major
roads in Massachusetts
We have also included in the zipped file a saved ArcMap document, 11.188_lab2_web.mxd, referencing these five shapefiles plus a sixth shapefile, matown00.shp, that is *not* included in the zipped file and is supposed to show the Masschusetts town boundaries. Use Windows Explorer to copy cambridge_shapefiles.zip to C:\TEMP and then right-click the zipfile and use the '7-zip' application to extract all the compressed files into C:\temp\cambridge_shapefiles. Next, navigate in Windows Explorer to C:\temp\cambridge_shapefiles and double-click on 11.188_lab2_web.mxd to start ArcMap and load the various shapefiles along with some of the MassGIS and ESRI web services that can provide useful background and foreground visuals.
When ArcMap opens the document, most of the shapefiles should be found and displayed in the Table of Contents and the data view window. However, the matown00 shapefile was not included in the zipped file. Right-click on that Table of Contents entry and choose Data/Repair-Data-Source to locate and reset that shapefile. It is located in the class data locker and it is small enough (and will not be changed by us) for us to use it directly from the network drive.
Finally, before starting our work, let's do one other thing to be sure we are set up for faster ArcMap processing. By default, ArcMap starts off assuming that your GIS 'workspace' and 'scratchspace' are both in your personal locker. But, for the WinAthena machines in the Lab and the CRON machines in the department, this location is in your network locker. In Lab #1, we included notes about how to change our default workspaces. To see if they are set to a local drive, choose the Geoprocessing / Environment menu option. Expand the first entry (workspace) in the environment list and check the 'Current Workspace' and 'Scratch Workspace' locations. Chances are it says, 'C:\Users\your-user-id\Documents\ArcGIS\Default.gdb' or something similar. Even if you followed last week's instructions to change your default workspaces to a truly local folder, ArcGIS will revert back to these default locations if it cannot find the 'scratch.gdb' geodatabase in the place (C:\temp) that you specified. For this week's lab, it will not matter much to specify truly local workspaces. You may choose to reset the 'current workspace' and 'scratch workspace' to be C:\TEMP\scratch.gdb. However, if this geodatabase does not already exit in C:\TEMP, you will need to use ArcCatalog to create it. Right-click the 'catalog' button on the right side of the ArcMap window, navigate within 'Folder Connections,' and right-click on C:\temp to choose 'New/file-geodatabase' to create C:\temp\scratch.gdb. If you do not see C:\temp in Folder Connections, click the 'Connect to Folders' icon in the tool bar at the top of the ArcCatalog window and add C:\temp as a connection. Finally, after doing all this, you may want to use 'File / Map-Document-Properties' in ArcMap to make sure that the Default Geodatabase is set to: C:\TEMP\scratch.gdb when you same your copy of 11.188_lab2_web.mxd.
Before we start using the file, let us also inform ArcMap of the appropriate geographic units to use. Open the Data Frame Properties (View Data Frame Properties from the menu bar) window and check that the "Map Units" are set to meters and the "Display Units" to feet. The 'map units' must be set to match the unit of measurement for the XY points that are saved in the shapefiles. If this information is saved in the 'metadata' portion of the first shapefile that is loaded into the Data Frame, then 'map units' will already be set and grayed out. We could use ArcCatalog to read or reset the metadata for any particular shapefile if we find that it is missing or incorrect. Beware that many shapefiles that you may find online do not have associated metadata. In our case, the 'map units' are meters and the correct metadata is saved as part of each of the shapefiles that we have loaded.. While the 'map units' must be set to match the coordinate system of the XY points saved in the shapefile, the 'display units' can be set to whatever units we would like to be shown on-screen. In our case, I suggest using 'feet' to emphasize that the display units can be different from the 'map units. Do you understand the difference?
Now that we have copied our lab exercise datasets to C:\temp, opened the provided ArcMap document and double-checked the data source and scratch space locations, we are ready to explore the data.
Exploratory mapping is the kind of mapping we do to get a feel for what the data "look like." Before coming to any conclusions, let's use ArcMap to make several thematic maps to examine various data attributes and raise questions that you would like to answer. We will go through a number of exploratory mapping techniques here.
Using the methods described in Lab 1, use the 'symbology' tab of the layer properties to modify the characteristics of the cambbgrp theme to match these criteria:
Use the Layer Properties window to change the name of this theme to Population. To change the number of decimal places, put the cursor on a label, click the right mouse button, and choose 'format labels.' It will open a Number Format window. Since numbers represent population, choose numeric and set the number of decimal places you want. In this case, be sure that the number of decimal places is set to 0. [Note, you can left click on the title 'Label' and select 'Format Labels' to set the values for use with all the labels.].
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You have created an unnormalized map of the Cambridge population by block group. Your map isn't as meaningful as you might like since your thematic shading depends only on the raw number of people in each block group - regardless of whether a block group is itself large or small. In such cases where your raw data are not 'normalized' (i.e., adjusted to represent a compared-to-something-meaningful comparison), it is easy to generate a pretty looking map that is quite misleading.(The Monmonier book, 'How to Lie with Maps,' in the class readings discusses such issues at greater length.) Shortly, we'll compare this thematic map with one that does normalize the population count. But, first, lets spruce up the map a bit.
By turning on the 'EOT Major Roads' layer within the 'Massachusetts Data
from MassGIS (GeoServer)' geoservices, we can overlay symbolized major
roads on top of our map. But the MassGIS web services are not always
available, and we have limited control over their use and symbology. The majmhda1.shp
shapefile included with today's datasets has the major roads in
Massachusetts. If the shapefile were not already included, we could click
on the Add layer button
,
and add majmhda1.shp from M:\data
. This is a MassGIS (Massachusetts Geographic Information
Systems) Major Roads Datalayer created in December 2000. However, it will
be faster to use the local (C:\temp) copy already on our local drive.
Turn off the MassGIS geoservices, and let's symbolize our major roads shapefile, majmhda1.shp, to display and symbolize an equivalent representation of major roads. First, change the name of the majmhda1.shp layer to Major Roads to make the entry in the table of contents more descriptive. Next, open the Layer Properties window, click the symbology tab, and set the properties as follows:
This is the first time we have used the "Unique Value" legend type. This type of legend is often useful when a field takes on only a limited number of discrete values. In this case, the field Class assumes only four values: 1, 2, 3, and 4. Each value represents a different type of road. These numbers are not very descriptive, so we will want to include text labels for each value. But what do the numbers mean? For that, we can consult the MassGIS metadata for State roads. The current MassGIS web pages describe a more recent version of the State Road layers. However, the definition of the Class attribute is still applicable. Use the descriptions for the values of Class to label your legend.
By default, ArcMap does not choose a very attractive symbolization scheme for the roads. You will need to adjust the symbols manually. Set the symbols as described in Table 1.
| Value | Color | Size | Style |
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Red |
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Solid |
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Blue |
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Solid |
| 3 | Dark Gray |
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Solid |
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Dark Gray |
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Dotted
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When you're done, your layer properties-symbology window should resemble Fig. 7. Note that you can edit the text in the 'labels' column if you need to change or expand the description of a category. If you make any edits, be sure to 'apply' your changes!
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Next, let's create a normalized map of the population data. Normalizing means dividing the variable of interest by a value (such as area) that enables the interpretation of the variable in the numerator to be more meaningful and not misinterpreted due to variations in polygon size that distort the way the data appears. Here, you can compensate for the effect of land area on population by dividing population by block group land area in order to measure population density. Larger areas typically have larger populations than smaller ones, but the actual densities of the areas may be quite different.
Create a new data frame by selecting insert "Data Frame" menu from the menu bar. You should now see the "New Data Frame" icon in the data frame window. Select the Major Roads layer under "Layers", click the right mouse button and select "copy". Then select the "New Data Frame", click the right mouse button and select "Paste Layer". Similarly, paste the Population layer into the "New Data Frame". Remember to set the Map and Display units for this new data frame.
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| Insert a New Frame | New data frame appears | Copy layers from existing frame | Paste layers to the new frame |
Open the layer properties to modify the Population layer. Adjust the number of decimal places to "1" and set the "Normalize by:" field to "Landacre." In ArcMap, the 'normalize by' option is used to pick an attribute that will be divided into the mapped attribute before doing the classification and shading. Hence, normalizing by landacre will create a population per acre measure. You should still be using the "Quantile" classification with 5 classes and "Orange Monochrome" color ramps. When you apply your changes, you will have a population density map. Change the layer's name to Population Density. Mathematically speaking, what did setting the normalization field do to the population values? Is the population density map more consistent with your impression of the parts of Cambridge that are more crowded? Also, compare the result when you normalize by the 'Area' attribute rather than the 'Landacre' attribute. The 'Area' attribute is the area (in square meters) of each block group polygon whereas the 'landacre' measure excludes bodies of water (like the Charles River Basin or Fresh Pond).
You have two data frames but the data view window displays only one frame at a time, so you need to activate a frame to see it. For example, if you want to see a data frame named, "New Data Frame," click the right mouse button with the mouse over "New Data Frame", and then select "Activate". (Note, you *can* show two maps within one "layout" view. We will cover that soon.)
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While a map often can tell a convincing story on its own, you can often strengthen your case with well-chosen labels and annotation.
You should be able to spot one or more areas in your two maps of
Cambridge where the discrepancy between the two maps is especially
apparent. In the original "Layers" frame (the unnormalized map), highlight
one of these areas by drawing a circle around the area with the Circle
tool 
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To select the Circle tool, you will first need to use Customize/Toolbars
to open the draw tool pop up menu as shown in table 2 and select Circle
from the pop up list of icons that appears. The complete list of drawing
tools is shown in Table 2.
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Once you've drawn the circle, you can use the Arrow Pointer tool 
to move and resize it.
You can change attributes such as the line thickness, outline color, fill
pattern, and so on using the Properties Window.
To open the properties window, double
click the circle you just created. You can also open the properties
window by clicking the right mouse button while placing
the cursor over the circle, and then selecting properties
from the bottom of the drop down list that appears. Make your circle have
an outline width of 3 and change the color to something that stands out,
yet doesn't clash with the color scheme of the map.
Now use the "A" Text tool
to add
some text annotation near the circle explaining why you put it there
(e.g., "Zone of High Discrepancy"). Use only a few words and choose font
characteristics that will make the text visible but not overwhelming. Note
that, as with the drawing tools, you can choose an annotation style from a
pop up list. You can experiment with these if you wish.
Labeling features on the map can help viewers orient themselves.
Labelling too many features, however, clutters up the map and impedes
readability. Let's put identifying markers on stretches of limited access
highways, symbolized by thick red lines on your map. Use the "i" Info tool
to look
at the attributes of the highways. Make sure that the Major Roads
layer is selected first. You will probably find that at least two records
show up for each click; that's because the two directions of the
multi-lane highways have been encoded separately, as if they were two
different routes very close to one another. If you watch closely as ArcMap
flashes the matching links, you can actually see this.
Interstate 90 (a.k.a. the Mass. Pike) extends east-west near the bottom of the image. As you identify links along this stretch, you should see that the "Rt-number" field is "90" and that the "Admin_type" is "1." From the metadata, you can see that an Admin_type of 1 indicates an Interstate highway. We want to label a few roads using their "Rt-number" field. Open the Layer Properties window for this theme. Click on the "Labels" icon and confirm that the "Label Field" is set to "Rt-number."
ArcMap has some nice cartographic goodies that will let us put highway
shields on the maps similar to those you've seen in commercial road maps
and the MassGIS and ESRI web services. Let's put some interstate highway
symbols on our map, but let's tell ArcMap to label only the Mass Turnpike
(I-90). Go to Menu Customize/Toolbars, select labelling
tool box. The labelling tools like fig 10. will appear in ArcGIS software.
Click the second button 
to bring up label manager dialogue and input 90 as a new class name and
click add (see table 3-1). A new class with name "90" will appear on the
left side. Right click "90" to select it, and select SQL Query to select
I-90 from the roads (see table 3-2). In the sql query input window, input
as shown in table 3-3, and click OK. Next, click the "Symbol" button 
, then select the "U.S.
Interstate HWY" shield among many label styles, you can use the search
function to find the shield (see table 3-4). Now click Apply
to see the the shield to appear on I-90, and click OK to
exit the labelling tool box. (We will use similar SQL query windows during
the next few labs to select map features based on the values of the
feature attributes.)
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Fig 10. Labeling Tool
Bar
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Table 3-1. add a new class
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Table 3-2. make a query to select
I-90.
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Table 3-3. the SQL query
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Table 3-4. select the symbol for I-90
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The ArcMap interface for labeling is not the most intuitive interface design. Take advantage of this opportunity to examine the ArcGIS Help files for more information about labeling. At some point during the exercise, be sure to spend some time exploring these help files. They contain many useful illustrations and discussion. Don't just focus on help about labeling. The online help on symbolizing maps and classifying datasets is also quite informative. [Beware that, on some WinAthena machines, opening the help files from the '?' buttons on various tool property windows will result in some error messages concerning javascripts that cannot be found. Ignore these messages (by clicking either 'yes' when asked several times about continuing) and the help files should eventually appear. If they do not, you can always start the same ArcGIS help files from the Start/Programs/ArcGIS menus.]
Other limited access highways visible in this view are Interstate 93, Mass. State Route 2, and a tiny stub of US 1. Place labels on I-93 and Mass. 2 and ignore US 1. Note that Mass. 2 should not get an Interstate shield since it is a state highway (Admin_type = 3); instead use a round, square, or oval shield. The full set of label tools is shown in Table 3. ArcMap gives you some control over the fonts and colors that appear in the shield symbols. To alter the settings, you may open the Layer Properties window, select the Labels tab and click the Symbol button to open the Symbol Selector window, which gives you the chance to alter the settings. You can experiment with this if you wish, but it is not necessary for this exercise.
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In Lab 1, you created a basic layout and made some simple customizations to it. Now, let's create a more elaborate layout that shows the comparison between the normalized and unnormalized population data. Before proceeding, however, we suggest that you save your ArcMap document. In fact, you may want to save the document twice, once as lab2_part3a.mxd to archive the current state and again, as lab2_part3b.mxd (or some other name), so you have a fresh copy in case subsequent edits corrupt the working document.
Since you have two data frames, if you create a layout view, both data frames will be shown in the layout. Use View Layout view to create a default layout using the "Portrait" template. Now you can see two frames in the layout. Adjust the size and location of each frames so they are readable. Click the right mouse button while putting the cursor on a data frame to check the properties of the frame.
In this layout we want the two view frames to be the same size and lined
up vertically, with "Layer" frame higher on the page than "New Data
Frame." Fortunately, ArcMap has tools to resize and align layout elements.
Select the Arrow Pointer tool . Move "View1" near the top of the page and
"View2" near the bottom, resizing or relocating them, if necessary, so
that they both fit. (You may also want to move any text, legend, or other
layout elements that we will add in subsequent sections.) ArcMap provides
some tools to help you rearrange the map views. For example, you can mouse
over a map in the layout window, click the right mouse button, and choose
Align Center, or Align Left, ...
from the Align menu. Note also that this
resizing changes the scale of the map but not the portion of the map that
is viewed. You can do this by going back to the Data View and pan, zoom,
or change the map scale.
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Now let's spiff up the frames by adding a border line around their edges. Select one of the view frames and click the right mouse button. Choose properties from the bottom of the drop down menu list. Properties window will come up. Select Frame tab then set the characteristics of border lines as you wish (we recommend keeping default settings for this lab.) and click OK. You should see a black line forming a tight box around the view frame. Repeat this procedure for the other view frame.
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Next, you need a legend, a scale bar, and a north arrow to improve the layout view of the map. First, let's insert a legend for the "Layers" frame, Activate the view frame either by clicking it or clicking the name of data frame(Layers) and then clicking the right mouse button, and select "activate" from the drop down list. Now select the Insert menu from the menu bar, and select legend. The Legend Wizard window will come up. Using the legend wizard, you can choose which layers will be shown in the legend. For this exercise, select all the names of layers shown in Map Layers space. Selected layers will be shown in the Legend Items space. Click Next. Change the legend title, set font, color and click Next. Now you can choose border line characteristics. Click Next and set spacing between the parts of your legend and click Finish. The legend will show up on the layout view. Follow the same steps, create a legend for "New Data Frame". Also, insert scale bars and north arrow for both view frames.
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| Fig. 14. Select Legend Items | Fig. 15. Set Legend Title |
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| Fig. 16. Set Border Line | Fig. 17. Set Spacing between Parts |
Finally, round off your map by setting the title of the layout to "Population of Cambridge, MA, 1990" and adding your name, today's date, and appropriate credits to the data source. When you're happy with the way that it looks, save your map as an ArcMap document file (with suffix, mxd). Later on, we will also explain how to save it as a PDF file that you can submit to our Stellar website for homework.
In this section of the lab we will create an explanatory map that makes a specific point by carefully choosing data, normalization, classification, etc. that visualizes a particular pattern or relationship in a manner that appropriately interprets the data.. Explanatory maps try to zero in on more specific questions than exploratory maps. Hence, your choice of normalization, classification methods, and the like should be suited to the particular relationship or hypothesis that you postulate. Here we will ask -- and suggest an answer to -- the question, "What is the relationship between land use and home prices?"
Open a new empty document (or start up a second instance of ArcMap) and add at least these data layers from your local directory (C:\TEMP):
Open the table for Landuse85.shp (click once on the layer to activate it and click right mouse button and select Open Attribute Table).. The field called "Landuse" is the primary one that is of interest to us. This shapefile is the Cambridge portion of the land use maps that MassGIS maintains for the State. We have all the data we need in our C:\temp folder, but you could obtain updated shapefiles and further documentation from MassGIS. (via the 'land use' links in the 'Physical Resources' section of the 'vector data' group.)
Highlight several rows of the table by clicking and dragging your mouse down the gray rectangles at the left side of each row. You might also experiment with the Selection/select-by-attributes option on the main menu to select rows that satisfy some condition that you specify. For the thematic map that you will prepare shortly, we ask you to highlight only that row in the table that corresponds to the part of Cambridge with " Multi-Family Residential (RO)' landuse and, among those regions with this landuse, with the second-highest area (as indicated in 'area_acres'). Note that you can sort the table based on any column by clicking on the column heading.
Before moving on to the next section, use the Selection/clear-selected-features option to get rid of any selections so that none of the features are highlighted.
Open the layer properties for Landuse85.shp. Change the "Symbology" to "Unique Value" and select "Landuse" as the "Values Field" then click "Add All Values." Your data is now classified by land use category. Notice that the colors the program automatically chooses are quite random. You can edit them manually, but MassGIS (and associated state and federal agencies) have already standardized sets of colors to use to designate various land uses. We have saved these symbology settings in a form that you can import into ArcMap. Notice in the top right-hand corner of the window an Import button. If you click the Import button, you can import symbology definitions from other layer files or import symbology definitions from an ArcView (a previous version of ArcMap) legend file.
Fortunately for you, a legend was previously prepared for this layer using ArcView. Click the 'import ... from an ArcView 3 legend file' button in the 'import symbology' window, navigate to the usual C:\TEMP directory and select the file landuse.avl (the avl stands for ArcView legend). Click OK. Your layer should pick up the saved symbolization choices. By default, ArcMap orders the categories (values) alphabetically, but we would rather group the residential categories together and have them at the top of the legend. Moving the categories helps us understand them better and will "read" much better on our final map. To move categories, simply click on a symbol and click the up and down arrow buttons on the right side of the window. Locate it where you would like it to be. Move the residential categories to the top:
Open the layer properties for Sales89. Using "Realprice" as your "Classification Field," try out the "Legend Types" "Graduated Color" and "Graduated Symbol." Also try the classification schemes "natural breaks," "quantile," and "equal interval." Remember the question we were interested in? Have these exploratory symbolization exercises shown you the relationship between sale price and land use? It's very difficult to see any type of pattern with so many data points, especially in a place like Cambridge, where high and low income neighbourhoods are so close together. We'll now abandon the automatic classification settings and use some of our expertise to determine the classes. We'll look only at very high-priced properties and very low-priced properties. Change the number of classes to "3" in the layer properties - Symbology tab and click Classify button. Change the first number shown in "Break Values" from something like 490196 to 100000 and second number to 750000. Now you have three categories, less than 100000, more than 750000, and in between. Click O.K. and Change the color and size of second category (realprice from 100000 to 750000), so that extreme values, lower than 100000 and higher than 750000, stand out. Give the points bright colors that will show up on top of the land use layer. Notice that the high-priced properties are in the lowest density areas. We're on our way to developing an explanatory map that helps visualize a spatial relationship that we deem to be relevant! (Later in the semester, and in other classes such as 11.220 and 14.30, we will discuss ways of determining whether the relationsihps are more than coincidence. We will also discuss ways of quantifying the relationship - e.g., by comparing the population density of census block groups with the sales prices of houses in those block groups.)
We do not have time to cover all of the symbolization possibilities in ArcMap. The built-in ArcMap help has some useful examples of thematic maps. To see them, select Help Topics from the Help menu. The Help system can take some time to launch. When the ArcMap Help window appears, click once on the "Contents" tab, double-click on the "Creating and Using Maps" book icon, double-click on the "Choosing colors and symbols" book icon, and double-click on "Types of thematic maps." For example, you may wish to change the symbol size associated with each sale so that it is larger for expensive homes. A good choice would be to make the radius of a sales 'dot' be proportional to the square root of realprice. (Do you see why you might want the square root?)
As an added refinement, tag your map with logos that can associate it with MIT and the department or computing lab. To do this, add a "picture frame" to your layout that includes a CRON or DUSP plus an MIT logo. You will need to use Insert Picture menu to insert onto your map the small MIT logo plus either the CRON logo or the following Urban Studies and Planning department logo. They can be found (as JPEG or GIF files) in M:\data\images
Finally, highlight the landuse feature (as discussed earlier) that corresponds to that part of Cambridge with "Multi-Family Residential (RO)' landuse and, among those regions with this landuse, with the second-highest area (as indicated in 'area_acres'.)
Make sure to save your map document file (e.g., as lab2_part3a.mxd) before continuing with the next part of this exercise. In fact, you may want to save it again as lab2_part4.mxd so your changes in the next section will not put your part 3 maps at risk.
We would like you to create one more map to illustrate some of the effects of showing a map in different projections. (We will discuss coordinate systems and projections shortly in lecture, and we would like you to examine the same map in different projections before we discuss the concepts and issues in more detail.)
Open up another Data Frame (via Insert / Data-Frame). Right-click the new data frame label, choose 'Properties' and click the 'coordinate system' tab. You will see that this new and empty Data Frame has 'no coordinate system.' In the upper portion of the 'Data Frame Properties' window, choose Predefined/geographic-coordinate-systems (to choose lat/lon coordinates instead of projected coordinates) and then pick 'north-America' and 'north American datum 1983' . Click OK so that the coordinate system of the new (empty) data frame is changed to be lat/lon using the North American Datum of 1983 (as the model of the surface of the Earth). Now, copy and paste the Cambridge landuse layer 'landuse85' from the original Data Frame into the new Data Frame. Since the 'landuse85' shapefile has been saved with metadata explaining that its features are stored in Mass State Plane coordinates, ArcMap knows how to transform it into lat/lon coordinates and it will do so on-the-fly when you paste the shapefile into your new Data Frame. Notice how the shape of Cambridge will look a little different when viewed in lat/lon coordinate rather than Mass State Plane coordinates (as shown in the original Data Frame). Create a layout with two maps showing Cambridge in the original Mass State Plane and the lat-lon coordinates. Label and annotate your map (with the north arrow, your name, etc. as discussed in the previous section) and add a sentence or two of text commenting on the difference between the two representations of Cambridge land use.
There are a number of reasons you might want to do something with your map other than print it from ArcMap. You may want to create a JPEG or PDF file for use on the web or just get the map into a graphics program to add some finishing touches. Here we consider two popular formats.
PDF format: This is a format we will use often. Files in this format can be read using a free program called Acrobat Reader. This program comes in a standalone version and as a web browser plugin. There are also other free pdf readers. The benefit of the PDF over a JPEG and other bitmap formats is that its resolution is independent. You can zoom in and out of the map and print it at any scale. To create a PDF file from your layout in ArcMap, select File Export Map. The Export window will show up. From the Export window, select the file location, choose "PDF(*.pdf)" option for Save as type, type the File name you want, then click Export.
JPEG format: Follow the same step describe above and choose "JPEG(*.jpg)" as Save as type. Unfortunately, JPEG uses "lossy" compression, meaning that a JPEG image is not fully faithful to the original. Artifacts caused by the lossy compression are often visible in JPEG versions of maps. Also, like any bitmap format, JPEGs have a fixed resolution, limiting the ability to zoom in effectively. JPEGs are useful for overview graphics on web pages, while PDFs can be used to supply the full detail (as long as the program creating the PDF chooses to retain the full detail.)
The MIT Libraries maintains a GeoWeb server with many geospatial datasets that can be downloaded. We will make use of this GeoWeb later in the semester. If you would like to get started now, you can check out the site. Note that you will need MIT personal certificates to access portions of this site.
1. Create an exploratory map as described in III A, an explanatory map as described in III B, and the map from Part IV that compares the views in different coordinate systems,
Note: All the maps you produce should contain your name, a title, a readable legend (with some indication of classification choice for any thematic maps that categorize quantitative data), north arrow, scale bar, data source attribution, and a CRON (or DUSP) and MIT logo. It is OK if the first map (IIA) is a little messy (with all the streets and labels), but try to make the other two maps be less cluttered and more readable (as well as properly labeled and attributed).
2. Export the above three maps into .pdf format and upload your maps to
our Stellar website that we use to turn in homework exercises: https://stellar.mit.edu/S/course/11/sp17/11.188/index.html.
Navigate the site to the find the Homework page, select Lab Exercise #2, and follow the instructions to upload your PDF maps.
Since you are at MIT, it's pretty easy publishing your work on the web. As you can see from the file 'tree' displayed in Windows Explorer, you already have a folder named "www" under your I:\ drive. If you save anything in your public "www" folder, then it is automatically visible to the world on the Web. Now for this class, create a new folder named "11.188" under your I:\www folder. Then save your pdf files from part II-A in that folder. You don't have to create a special web page to do this. Just copy and paste your pdf file into the 11.188 folder you just created. The directory listing, including the PDF file, will now be visible in a browser at this URL: http://mit.edu/your-athena-name/www/11.188
You are not required to put a PDF version of your map in your WWW locker - and you may well not want to leave it there. We just want you to know that it is possible and how you can do it. The lab exercise requirement is to upload your three maps to the appropriate Stellar homework site.
Lab 2 is due by the beginning of the class on Monday, Feb. 27, 2017.
Created by Thomas H. Grayson. Includes
significant portions originally written by Raj Singh.
Modified for Fall 2000-15 by Thomas H.
Grayson, Myounggu Kang, Jeeseong Chung, Jinhua Zhao, Xiongjiu Liao,
Mi Diao. Yang Chen, Yi Zhu, Eric Schultheis and Joe Ferreira.
Last Modified 15 Feb. 2017 by Juan Camilo Osorio.
Back to the 11.188 Home Page. Back to the CRON Home Page.