Presentation on theme: "Introduction Coastal Population Growth, Thematic Visualization, and the Study Area Visualizing Population Growth along the Coast Exercise A Formatting."— Presentation transcript:
Introduction Coastal Population Growth, Thematic Visualization, and the Study Area Visualizing Population Growth along the Coast Exercise A Formatting Data for AnalysisAnalysis and Display of Demographic Data Exercise B Estimated Length: 2.5 Hours
Coastal Applications Using ArcGIS Visualizing Population Growth Along the Coast2-3 Module Introduction Currently, over 50 percent of the nation’s population lives within close proximity of the coast. Population growth rates along the coast are increasing at an alarming rate, placing a strain on the surrounding marine and estuarine ecosystems. Geographic information system (GIS) software can be used in conjunction with demographic data to visualize population growth and its effects on the environment. In this module you will import census demographic data, join the data to an existing shapefile’s attribute table, and calculate, classify, and map certain population parameters. Use and understand census data Join and relate tables Add and calculate table fields Use various legend classifications and symbols Create maps with multiple data frames ArcGIS Components ArcMap ArcGIS Extensions Spatial Analyst Geoprocessing Tools Select By Location Tools and TechnologyOverview Skills Learned
Coastal Applications Using ArcGIS Visualizing Population Growth Along the Coast2-5 Introduction: Coastal Population Growth Background Coastal areas comprise only 10 percent of U.S. land areas, but are home to over half of the nation’s population. By the year 2010 coastal population is expected to increase by another 60 percent. 14 of the nation’s 20 most populous cities are in the coastal zone. Effects of Population Growth Population increase means more potential damage to habitats (since 1970 there have been 2000 homes per day erected in coastal areas!) Increased development creates more impervious surfaces Increased pollution causes oxygen depletion May cause fish kills and algal blooms
Coastal Applications Using ArcGIS Visualizing Population Growth Along the Coast2-6 Introduction: Coastal Population Growth GIS and the Coastal Context GIS can be used to visualize population growth, as well as its effects on the environment Population data are readily available from the U.S. Census Numerous state environmental agencies provide pollution and water quality data Analysts can create land cover change data from remote sensing integrated with GIS Coastal monitoring programs provide sources of data that can be imported into a GIS GIS can be used to plan future growth that minimizes harmful effects on coasts
Coastal Applications Using ArcGIS Visualizing Population Growth Along the Coast2-7 Introduction: Thematic Visualization Features and Attributes The power of a GIS stems from the link between the attribute information and the geographic, or spatial, features You can add attribute information manually in ArcMap or join an external table of attribute values If attributes are quantities, then you can map their magnitudes FeatureAttributes
Coastal Applications Using ArcGIS Visualizing Population Growth Along the Coast2-8 Introduction: Thematic Visualization Symbolization How you represent your data determines what your map communicates Before you can map quantitative data, you must classify the data into different groups The most popular method to symbolize quantities (such as population data) is through graduated colors Larger quantities are represented by darker colors
Coastal Applications Using ArcGIS Visualizing Population Growth Along the Coast2-9 Introduction: Thematic Visualization Creating the Perfect Map Layout All maps should have A clear title A representation of scale A north arrow A legend Source information Your map layout should have a balanced appearance
Coastal Applications Using ArcGIS Visualizing Population Growth Along the Coast2-10 Introduction: Study Area Waquoit Bay NERR 2,500 acres located on the south shore of Cape Cod in the State of Massachusetts Encompasses open waters, barrier beaches, marshlands, and uplands Because of surrounding coastal population growth, primary research is focused on nonpoint source pollution Wells NERR Protects fields, forests, salt marshes, and sandy beaches on the southern coast of Maine Research interests include Investigation of Gulf of Maine estuaries, salt marshes, and watersheds Production of information needed for sustaining or restoring these coastal habitats and communities
Coastal Applications Using ArcGIS Visualizing Population Growth Along the Coast2-11 Exercise A: Formatting Data for Analysis Background As a coastal resource manager, you are concerned with the health and vitality of the nation’s coastal areas. With coastal populations on the rise, you are particularly interested in marine protected areas and how they are responding to the human activities outside their borders. In this exercise you will look at National Estuarine Research Reserves (NERRs) in New England and determine the areas of influence around them. One of the challenges will be dealing with the differences between natural and physical boundaries. Physical processes may occur within natural boundaries, but data are often available and management decisions made in accordance with political boundaries. Therefore, you will have both watershed and county boundaries to work with. Once you have determined your areas of influence, you will also need to find and incorporate demographic data for those areas in preparation for Exercise B. Objectives 1.Reselect watersheds that intersect NERRs boundaries 2.Reselect counties that intersect and influence these watersheds 3.Join the table containing population statistics and demographic data for 2000 with the county shapefile table Goal After hearing the lecture and working through the exercises, the student will be able to select features based on location and create new layers containing these data. The student will also be able to find and understand census data, as well as be able to join this and other tabular data to existing shapefiles.
Coastal Applications Using ArcGIS Visualizing Population Growth Along the Coast2-12 Exercise A: Formatting Data for Analysis Summary of Process Steps 1.Select New England NERRs by Location – Create a new shapefile of the NERRs that are located in the New England states 2.Select Watersheds by Location – Create a new shapefile of watersheds that intersect the New England NERRs 3.Select Counties by Location – Create a new shapefile of counties that have significant area within the chosen watersheds 4.Join Table to Shapefile – Join the 2000 demographic data to your county shapefile Select by Location Use this function to select features based on their location relative to another feature Join Data Use this function to append additional data to a layer’s attribute table Tools to Use Data New_England.mxd ArcMap document states.shp Polygon shapefile of U.S. states NERRs.shp Polygon shapefile of U.S. NERRs ne_states.shp Polyline shapefile of New England states ne_watersheds.shp Polygon shapefile of New England watersheds ne_counties.shp Polygon shapefile of New England counties NERR_counties.lyr Polygon layer file of counties that intersect with NERRs ne_dem_2000.dbf Database table of census demographic data
Coastal Applications Using ArcGIS Visualizing Population Growth Along the Coast2-13 Exercise A: Formatting Data for Analysis 1. Select New England NERRs by Location To begin, start ArcMap. When prompted, select to start the program with an existing map, navigate to the Pop_Growth data directory and select the New_England.mxd map document file. Turn on the NERRs layer. Notice that the NERRs layer, showing the nation’s estuarine research reserves, is hard to see unless you turn off the states layer. Instead of turning off the states layer, you can make it partially transparent. Double-click on the states layer to open the Layers Properties dialog box. Click on the Display tab, and set the Transparent value to 75%. Click OK. Turn on ne_states, and zoom to that layer. For this exercise you are only interested in NERRs located in New England. Performing a Select By Location operation will allow you to select only those NERRs that lie within this geographic area. We will then export these selected locations to a separate layer. You can make raster, Triangulated Irregular Network (TIN), and feature layers transparent in scenes and maps. For example, you can use transparent layers to You can also use the Adjust Transparency tool on the Effects toolbar in ArcMap to set the transparency for a layer Did You Know? Visualize data that are scattered above and below a reference plane Compare two surfaces Show terrain and subsurface features at the same time
Coastal Applications Using ArcGIS Visualizing Population Growth Along the Coast2-14 Exercise A: Formatting Data for Analysis 1.Select New England NERRs by Location (continued) On the menu bar, click Selection > Select by Location. Choose to select features from The NERRs layer That intersect The features in the ne_states layer Click Apply and Close
Coastal Applications Using ArcGIS Visualizing Population Growth Along the Coast2-15 Exercise A: Formatting Data for Analysis 1. Select New England NERRs by Location (continued) Click on Selection > Zoom to Selected Features to get a better perspective of the NERRs you selected. As you can see, there are four National Estuarine Research Reserve sites within New England: one each in Maine, New Hampshire, Massachusetts, and Rhode Island. They are the Wells NERR, Great Bay NERR, Waquoit Bay NERR, and Narragansett Bay NERR, respectively. To create a separate shapefile of just these selected sites, right-click on NERRs and choose Data > Export Data. Export the selected features using the same coordinate system as the layer’s source data, and save it as ne_nerrs.shp in your Pop_Growth directory. Choose Yes to add the data to your map. Right-click on NERRs, and choose Selection > Clear Selected Features. Turn off the data layer. Again, your new NERRs layer may be hard to see until you change the color. Double-click on the symbol box of ne_nerrs and change the fill color to a bright red. Change the outline color to red as well. Click OK. For more information on the National Estuarine Research Reserve System visit Web Sites
Coastal Applications Using ArcGIS Visualizing Population Growth Along the Coast2-16 Exercise A: Formatting Data for Analysis 2. Select Watersheds by Location Now that you have the New England NERRs, you need to know which watersheds they are a part of. Turn on the ne_watersheds shapefile. Choose Selection > Select By Location. Set the parameters so that you are selecting features from the ne_watersheds layer that intersect with the ne_nerrs layer. Click Apply. Close the dialog box when it is finished. Zoom in on the selected watersheds. In the table of contents, right-click on ne_watersheds and choose Selection > Zoom to Selected Features. Note that this is the second method you have used to zoom to selected features in this module. This is one of many ArcMap functions that are duplicated throughout the program. Right-click on ne_watersheds and export the data as a new shapefile to the Pop_Growth directory. Name it nerr_watersheds. As before, export just the selected features and use the source data layer’s coordinate system. Choose to add the new data layer to the map. Watersheds are “That area of land, a bounded hydrologic system, within which all living things are inextricably linked by their common water course and where, as humans settled, simple logic demanded that they become part of a community." John Wesley Powell scientist and geographer Remember – no matter where you are, you're in a watershed! Did You Know?
Coastal Applications Using ArcGIS Visualizing Population Growth Along the Coast Select Counties by Location We are finished with the ne_watersheds layer. Clear the selected features and turn the layer off. You will now select the counties that contain these watersheds and, therefore, that influence the NERR sites. Turn on the ne_counties layer. It is difficult to see the county borders underneath the watershed polygons. Making nerr_watersheds partially transparent will allow you to view both layers and all their boundaries. Also, if your new shapefiles are assigned colors that are not easy to distinguish from the others, always feel free to change the symbol color. Make the transparency level 40% for the nerr_watersheds layer. From the menu bar, click on View > Bookmarks. Select RI_watershed. Right-click on ne_counties, and choose Label Features. Exercise A: Formatting Data for Analysis A spatial bookmark identifies a particular geographic location that you want to save and refer to later Bookmarks are easy to create. Once you have your data view set to a particular area, simply go to View > Bookmarks > Create As you pan and zoom within your map, you can easily return to the study area by accessing the bookmark Did You Know?
Coastal Applications Using ArcGIS Visualizing Population Growth Along the Coast2-18 Exercise A: Formatting Data for Analysis 3. Select Counties by Location (continued) You are looking at the area surrounding the Narragansett Bay NERR in Rhode Island. As you can see, the watershed for this area overlaps several counties – some more than others. For example, Worcester and Plymouth counties each have substantial areas within the watershed zone. Middlesex County, on the other hand, overlaps the watershed by just a small piece. You want to select only those counties with at least a moderate impact on the watershed area. Open the Select By Location dialog box. Select features from the ne_counties layer that have their centers in features from the nerr_watersheds layer. Click Apply. Do not close the dialog box just yet... Move the dialog box to the side, and see that many of the influencing counties surrounding the NERR have been selected, but not all of them. You will now add to your selection those counties that do not have their centers within the watershed region, but are still considered significantly within the watershed. In ArcView 8, the Select By Location function is very robust, allowing the user to select many different parameters defining the relationship between two layers. Some of these parameters include Touch the boundary of Share a line segment with Are crossed by the outline of These parameters give the user more choices to define spatial relationships than those found in ArcView 3 Did You Know?
Coastal Applications Using ArcGIS Visualizing Population Growth Along the Coast2-19 Exercise A: Formatting Data for Analysis 3. Select Counties by Location (continued) For your next selection in the Select By Location dialog box, choose to add to the currently selected features Make sure ne_counties is selected Choose those features that are within a distance of Features in nerr_watersheds You will notice that the option to enter a distance buffer becomes available. Enter –2, and change the units to miles. This will select those counties that overlap the watershed by at least 2 miles Click Apply and close the dialog box when the selection process is complete
Coastal Applications Using ArcGIS Visualizing Population Growth Along the Coast2-20 Exercise A: Formatting Data for Analysis 3. Select Counties by Location (continued) Right-click on the ne _counties layer and turn off the labels. Then choose to zoom to the selected features. (There are two different ways to do this – do you know them both?) Export the selected features to create a new shapefile. Name this layer watershed_counties.shp and save it in the Pop_Growth folder of your student directory. Choose Yes to add these data to your map. Clear the selected features from ne_counties and turn the layer off. Rearrange your table of contents so that the top three layers are ne_nerrs, nerr_watersheds, and watershed_counties in that order from top to bottom. To move a layer, simply highlight it and drag it up or down in the table of contents. You now have those counties that influence the New England NERR sites selected and in a separate shapefile to work with for the rest of this exercise. Why was it important to select counties that overlapped with the watershed regions, instead of just those that intersected with the boundaries of the NERRs? _______________________________________________________________________________________________
Coastal Applications Using ArcGIS Visualizing Population Growth Along the Coast2-21 Exercise A: Formatting Data for Analysis 3. Select Counties by Location (continued) To see a comparison, add nerr_counties.shp to your map. This layer can be found in the Pop_Growth data folder. The area around Narragansett Bay NERR is a good example of how many counties would have been missed without considering the watershed coverage. Remove nerr_counties from the table of contents. 4. Join Table to Shapefile In the next exercise you will calculate the population change between 1990 and In order to do that, you will join a table of 2000 demographic statistics, including population, to your watershed_counties layer. Open the attribute table for the watershed_counties layer. Use the Add Data button and subsequent file dialog to add the table called ne_dem_2000.dbf to the map document from the Pop_Growth data folder. This table is the previously mentioned aggregate file of Census TIGER data, and contains the demographic data for all the New England counties. TIGER ® stands for Topologically Integrated Geographic Encoding and Referencing The TIGER/Line files are a digital database of geographic features, such as roads, railroads, rivers, lakes, political boundaries, census statistical boundaries, etc. covering the entire United States The TIGER/Line files are downloaded in compressed shapefile format for a selected county or data layer Did You Know?
Coastal Applications Using ArcGIS Visualizing Population Growth Along the Coast2-22 Exercise A: Formatting Data for Analysis 4. Join Table to Shapefile (continued) You may not initially see ne_dem_2000 in the table of contents (TOC). If this happens, click on the Source tab on the bottom of the TOC. Right–click on the file and then open the table. Arrange the two tables so you can view the field headings of both at the same time. In order to join two tables they must share a common field, known as a common or primary key. Look at the column titled “FIPS” in the watershed_counties table. Compare that to the “STFID” column in the ne_dem_2000 table. They have different headings, but both contain unique identifying numbers referring to the same thing. (The first two numbers are the state code, and the last three numbers are the county code). You will use these fields as the common key for the tables. Remember, watershed_counties is a subset of counties you created from ne_counties so it does not contain records for every county in New England, as ne_dem_2000 does. You are only interested in the information from ne_dem_2000 that corresponds to the counties in your watershed layer. Close both attribute tables. If you have information stored in a table, such as a dBASE, INFO, or geodatabase table, you can associate it with your geographic features and display the data on your map by one of two methods: Joining tables – appends the attributes from one table onto the other based on a field common to both tables Relating tables – defines a relationship between two tables— also based on a common field—but doesn't append the attributes of one to the other. Instead, you can access the related data when necessary Did You Know?
Coastal Applications Using ArcGIS Visualizing Population Growth Along the Coast2-23 Exercise A: Formatting Data for Analysis 4. Join Table to Shapefile (continued) Since you will be joining data to the attribute table of the watershed_counties layer, double-click on the layer to open its Layer Properties. In the Layer Properties box, click on the Joins & Relates tab. Under Joins, click the Add button Make sure the first pull-down menu is set to Join attributes from a table Choose FIPS as the field to base the join on Choose ne_dem_2000 as the table being joined Choose STFID as the other field to base the join on Click OK to process the join and close the dialog
Coastal Applications Using ArcGIS Visualizing Population Growth Along the Coast2-24 Exercise A: Formatting Data for Analysis 4. Join Table to Shapefile (continued) Bring up the Layer Properties for the watershed_counties layer and click on the Fields tab. Examine the new fields that have been added. You will have to widen the Name field to view the field titles in this table. Notice that the title now includes the name of the table it originated from. This is particularly helpful when you have commonly named fields. Close the Layer Properties dialog and any open tables in the map document. Save your map document, as the changes you made will be used in the next exercise. Exercise Summary In this exercise you selected NERRs in New England, selected watersheds that intersected with the New England NERRs, and selected counties that were significantly within those watersheds. You did this to find the counties whose populations and activities have an influence on the NERRs. Once you had these counties, you were able to join Census TIGER data to your county shapefile. In the next exercise you will use this and other demographic data to look at and map various population and environmental parameters. END OF EXERCISE A
Coastal Applications Using ArcGIS Visualizing Population Growth Along the Coast2-25 Exercise A: Formatting Data for Analysis p. 20 Why was it important to select counties that overlapped with the watershed regions, instead of just those that intersected with the boundaries of the NERRs? When investigating potential effects on NERRs, it is important not to focus at too small a level. By focusing the investigation at the watershed level, it is possible to look at all potential cause and effect relationships. All the counties that are within the watershed for a particular NERR have the potential to have some effect on that reserve. If you looked only at those counties that intersected with the NERR, you would be limiting the effectiveness of the research. Answers to Exercise Questions
Coastal Applications Using ArcGIS Visualizing Population Growth Along the Coast2-26 Discussion: Applying These Skills Elsewhere Can you think of other scenarios where political vs. natural boundaries could be an issue? __________________________________________________________________________________ __________________________________________________________________________________ __________________________________________________________________________________
Coastal Applications Using ArcGIS Visualizing Population Growth Along the Coast2-27 Exercise B: Analysis and Display of Demographic Data Background Now that you have determined the areas influencing the New England NERR sites, your interests will focus on the population changes and demographics of these areas. After looking for areas of especially high population change, you will concentrate on Barnstable County, Massachusetts, the location of the Waquoit Bay NERR. It will be up to you to determine which county demographic data are most important to consider for coastal management purposes and the best way to display the information you have. Goal After hearing the lecture and working through the exercises, the student will be able to use census and other tabular data to calculate and represent population changes. The student will also have the skills to display demographic information in an appropriate and meaningful way. Objectives 1. Perform table calculations 2. Use and understand different legend classifications 3. Create a map layout using multiple data frames
Coastal Applications Using ArcGIS Visualizing Population Growth Along the Coast2-28 Exercise B: Analysis and Display of Demographic Data Summary of Process Steps 1.Add and Calculate a New Field – show the population change between 1990 and Display Population Data – look at several population parameters including total population, population density, and population change 3.Join Tables – join demographic data to a county shapefile 4.Use Different Classification Methods – use and understand the various classification schemes available in ArcMap 5.Layer Symbology – learn more about the tools available to effectively display your data 6.Choose and Map a Demographic Parameter – Choose and map a specific parameter using the classification methods and symbolgies you learned in the exercise Field Calculator Use this tool to perform mathematical calculations to set a field value for a single record or all records Join Data Use this function to append additional data to a layer’s attribute table Tools to Use Data New_England.mxd ArcMap document nerr_watersheds.shp Polygon shapefile of watersheds adjacent to NERRs watershed_counties.shp Polygon shapefile of watershed influencing counties trt25001.shp Polygon shapefile of Barnstable census tracts t dbf Database table of Barnstable demographics trt23031.shp Polygon shapefile of York census tracts t dbf Database table of York demographics
Coastal Applications Using ArcGIS Visualizing Population Growth Along the Coast2-29 Any changes that you make to a feature or attribute table in an edit session are not saved to the actual file until the edit session is closed. This means that changes can be undone while an edit session is open It is possible to make some changes to a feature or attribute table without opening an edit session, but any changes you make cannot be undone Exercise B: Analysis and Display of Demographic Data 1. Add and Calculate a New Field If necessary, start ArcMap and open the NewEngland.mxd map document you saved from the previous exercise. Open the Attribute Table for watershed_counties. You will now create a new field to show the population change from 1990 to In the Attribute Table click on Options > Add Field. Name the new field pop_chng and change the Type to Long Integer. Click OK. The new field will be inserted as the last column of the original data set, in this case the last column with watershed_counties in the title. Start an edit session by clicking on the Editor pull-down menu on the Editor toolbar and choose Start Editing. (NOTE: You may get a “Starting to Edit in a Different Coordinate System” dialog box. Simply press Start Editing.) Right-click on the new field header and choose Calculate Values. In the Field Calculator, set the expression to read [ne_dem_2000.POP2000] – [watershed_counties.POP1990] Click OK. Did You Know?
Coastal Applications Using ArcGIS Visualizing Population Growth Along the Coast2-30 Exercise B: Analysis and Display of Demographic Data 1. Add and Calculate a New Field (continued) After the calculations have completed, take a moment to look at the numbers. It may be easier to put them in order. To do so, right-click on the field heading and choose Sort Descending. Which county has experienced the greatest population change? Does any one state appear to be changing more than the others? Have any county populations decreased? Which one(s)? _______________________________________________________________________ Close the Attribute Table when you are finished. Click on the Editor pull-down menu on the Editor toolbar and select Stop Editing. Click Yes to save the edits you made inside the edit session. Sometimes layer titles are longer than the spaces provided for them (as in the Field Calculator) and are hard to read. Rather than having to scroll over to read the full title, hold your cursor over the layer name for a second and the name will appear in its entirety Did You Know?
Coastal Applications Using ArcGIS Visualizing Population Growth Along the Coast2-31 Exercise B: Analysis and Display of Demographic Data 2. Display Population Data Now that you have joined the demographic data to the watershed_counties layer, you can use the new attributes to symbolize the layer. Zoom to the extent of watershed_counties and turn off the nerr_watersheds layer. Double-click on watershed_counties and select the Symbology tab if necessary. Choose to show Quantities and Graduated colors. For Value, select ne_dem_2000.POP2000. Drag the Properties box to the side so you can view your map. Click Apply. This is showing the population, or number of people, in the selected New England counties. While this is useful information, it may not be the best way to show the population of each county. Now you will look at population density, or the population per square mile. This can be done two ways. You could create a new field in the attribute table and calculate the population density (pop2000/area) as you did to find the population change. You can also normalize, or divide one attribute by another, and get the same result. Normalization can be done in the Symbology section of the Layer Properties box.
Coastal Applications Using ArcGIS Visualizing Population Growth Along the Coast2-32 Normalization – Creation of a ratio by dividing two data values. Normalizing data minimizes differences in values based on the size of areas or numbers of features in each area Exercise B: Analysis and Display of Demographic Data 2. Display Population Data (continued) With Value still set to ne_dem_2000.POP2000, select watershed_counties.AREA for Normalization. Click Apply. Notice how the classification of the counties changes on the map. Set Normalization back to NONE. Choose the field you created, watershed_counties.pop_chng, as the Value you want to represent on the map. Click Apply. This shows how much the population changed between 1990 and You have seen how displaying population data differently affects the map. When might you be interested in each of these three parameters: total population; population density; population change? _______________________________________________________________________ For the remainder of this exercise you will focus on a county that is experiencing a high degree of population change. As you can see on your map, the area around Waquoit Bay NERR on Cape Cod, Massachusetts, has undergone some of the highest levels of population change. We will look more closely at Barnstable County. Close Layer Properties. Glossary Terms
Coastal Applications Using ArcGIS Visualizing Population Growth Along the Coast2-33 Exercise B: Analysis and Display of Demographic Data 3. Join Tables You will now add two new items specific to Barnstable county. One is a shapefile of Barnstable county divided up by census tracts. The other is a table with the associated demographic data by census tracts. These data are Census TIGER files and were downloaded from the Geography Network Web site. Add trt25001.shp and t dbf from the data folder in your student directory. A warning box will pop up telling you that these items are in a different projection than your current map projection. Click OK. For the best possible alignment and accuracy you would want to actually change the coordinate system of the new layers, but for our simple viewing purposes, ArcMap’s “on the fly” projection change is sufficient. In the table of contents, change the layer name of trt25001.shp to Barnstable census tracts. Turn off all layers except Barnstable census tracts. Zoom to that layer. Open the tables for the Barnstable layer and t dbf. Scroll all the way to the right in t The common field for these tables is titled KEY. This is the field you will use to join the two tables. Close both tables. ArcMap supports projection on the fly, meaning that you can make a map in one projection (referred to as a coordinate system) and have your data stored in any number of projections To enable a feature layer to be projected on the fly, ArcMap needs to know the source coordinate system (for the layer) and the target coordinate system (for the map display) Did You Know?
Coastal Applications Using ArcGIS Visualizing Population Growth Along the Coast2-34 Exercise B: Analysis and Display of Demographic Data Join the table t to the Barnstable census tracts layer. (Remember, this is done through the Layer Properties box of the Barnstable layer.) 4. Use Different Classification Methods Open the Layer Properties for the Barnstable layer and click on the Fields tab. Scroll through the list of fields to see what new information is available to you. There are significantly more data fields at the census tract level than there were at the county level. Click on the Symbology tab. Under Show, select Quantities: Graduated colors. For Value, select t PERSONS. Move the Properties box to one side so you can view your map. Click Apply, but don’t click OK just yet... Notice where it says Natural Breaks (Jenks) in the Classification section of the Properties box. This is the default method of classification in ArcMap. This method uses natural groupings or patterns in the data to define classes and shows clusters or concentrations of values. More information regarding the various classification methods appears in the sidebar to the right. Also notice that a border of water surrounding Cape Cod is included in this layer and is being classified. Look at the classification ranges. The first one goes from 0 to Since we aren’t interested in the water area, we can assume it has zero “persons” and exclude it from our data display. There are four basic classification methods used in ArcMap: Natural Breaks – classes are based on natural grouping of data values Quantile – classes contain equal number of features Equal Interval – classes contain equal- sized range of values Standard Deviation – classes reflect amount of variation from mean Did You Know?
Coastal Applications Using ArcGIS Visualizing Population Growth Along the Coast2-35 Exercise B: Analysis and Display of Demographic Data 4. Use Different Classification Methods (continued) In the Layer Properties box under Classification, click on the Classify button. Click Exclusion. Under the Query tab in the Data Exclusion Properties dialog box, set the expression to read "t PERSONS" = 0 Under the Legend tab, make sure show symbol for excluded data is unchecked. Click OK. Click OK in the Classification box, and then Apply in the Layer Properties box. Not only does the map look better without the surrounding water area, those 0 values will no longer be incorporated into classification schemes, which could potentially skew the results. Click on the Classify button and change the Classification Method type to Equal Interval. Recall that this classification scheme divides the range of attribute values into equal-sized subranges. Click OK and Apply to see the changes on the map. What do you think of the changes? This map doesn’t show as much variety between counties. Click on the Classify button once again. Look at the distribution of the data on the chart. Notice that most of the data fall within two classes, so this classification type would probably not be the best choice for this data set.
Coastal Applications Using ArcGIS Visualizing Population Growth Along the Coast2-36 Exercise B: Analysis and Display of Demographic Data 4. Use Different Classification Methods (continued) What types of data may be better suited for equal interval classification? _____________________________________________________________________________________________ This time, change the Classification Method to Quantile. In a quantile classification, each class contains an equal number of features. Click OK and Apply to see the changes on the map. As you have seen, your map will look very different depending on the classification method and number of classes you choose to use. An important aspect of displaying any data is finding the combination best suited for your data and what you want the display to show. 5. Layer Symbology In addition to changing the way your data are classified, you have many other options available to display your data. In Layer Properties, under Show: Quantities, change from Graduated color to Dot density. Highlight t PERSONS in the Field Selection box, and click on the arrow to move it into the box on the right. Change the Dot Value to 500, and click Apply. Each dot represents 500 people.
Coastal Applications Using ArcGIS Visualizing Population Growth Along the Coast2-37 Exercise B: Analysis and Display of Demographic Data 5. Layer Symbology (continued) Next, change the Symbology to show Quantities - Proportional symbols. Select t PERSONS for the Field Value. This time you get a warning about this field having some zero values and you are asked to exclude them. Using the Exclude button in the Classify dialog, exclude the data where persons equal zero, just as you did previously. Click Apply. In this case, the symbol size represents total population values. To look at population density, normalize t PERSONS to the size of the counties. (In this case, t :LAND_KM). Areas of high population density are now much easier to distinguish. Under Show, click on Charts and select Pie. This type of symbology makes it easy to compare related fields. As an example, you’ll look at how people in this area get to work. About halfway down the Field Selection box, highlight and move to the right the fields DRVALONE, CARPOOL, and PUBTRANS. Click the Size button, and change the size to 22 pts. Click OK and Apply. Let’s say you are particularly interested in seeing the percentage of commuters who use public transportation. The color scheme is randomly assigned for the pie chart, but you can change it. Double-click on the symbol next to PUBTRANS in the Layer Properties box, and change it to bright yellow. Click Apply. Once you have classified your data, there are many different ways to symbolize data values. Color ramps are useful for symbolizing continuous values. Graduated symbols are useful for representing more discrete values Proportional symbols are useful in representing ratios in datasets Did You Know?
Coastal Applications Using ArcGIS Visualizing Population Growth Along the Coast2-38 Exercise B: Analysis and Display of Demographic Data Styles are an organized collection of symbols and map elements ArcMap starts with two default symbol styles: ESRI and a Windows- generated symbol set. Many other industry- specific (civic, weather, environmental, real estate, etc.) styles can be accessed at Tools > Styles > Style Manager There are over 12,000 symbols available in ArcMap 5. Layer Symbology (continued) Finally, change the classification back to showing population density in Graduated colors using Natural breaks. This task can be accomplished by selecting Graduated colors under Quantities and then normalizing the t PERSONS field by the t LAND_KM field. Don’t forget to set the classification method! Close Layer Properties. Did You Know?
Coastal Applications Using ArcGIS Visualizing Population Growth Along the Coast2-39 Exercise B: Analysis and Display of Demographic Data 6. Choose and Map a Demographic Parameter In this section you will choose a demographic parameter and create a map layout visualizing the parameter within your study area. Data for two different study areas is available to you: Barnstable County, MA, which surrounds Waquoit Bay NERR, and York County, ME, which surrounds Wells NERR. If you choose York County, you will need to add trt23031.shp and t dbf to your map document and join them based on the KEY field. Don’t forget to exclude the area off the coast in any classification you perform, as it contains no population. Choose a parameter that you think would be of interest to a coastal manager for the area. It can be one you have already worked with or a new one. Look through the attribute table and see what you can come up with. Feeling stuck? Start with something simple like population density, either as a graduated color or proportional symbol. Or show housing units using dot density. How about a pie or bar chart of residences that use public versus private sewage systems? You could show the ratio of housing units that are renter-occupied versus owner-occupied, rental rates by graduated color; areas that have a majority of seasonal residents; or areas with older homes – those built prior to Once you have chosen a parameter, classify and symbolize it using Layer Properties. Try to incorporate some of the different classification methods and symbology styles you have just learned about. When you have finished classifying and symbolizing your data, you may need to zoom to the extent of the layer you are working with. This will allow you to view all of your study area in your map. Click on the Layout View button found on the lower left of the map view window.
Coastal Applications Using ArcGIS Visualizing Population Growth Along the Coast2-40 Exercise B: Analysis and Display of Demographic Data 6. Choose and Map a Demographic Parameter (continued) Since you know that either of the counties that you may have mapped surround a NERR, it might be useful to display the NERR’s location on the map as well. Turn on the ne_nerrs layer and move it above the census tract layer you have been working with in the TOC. You may need to change the color of the layer and adjust the transparency value so that you can see both layers at the same time. Take a look at your map. What’s missing? All maps should have a clear title stating what is being mapped when and where, a north arrow to establish a sense of direction, a scale bar, a legend to define the quantitative values you have mapped, and source information for the data you used to produce your map (the data in this exercise were obtained from the U.S. Census Bureau). All of these items can added to your map using the Insert menu. Once you have inserted these items, you can select them and move them around. You can also select each element and right-click to access more placement options. You can always change the name of your layers by double-clicking on the layer in the TOC and selecting the General tab in the Layer Properties dialog. Make sure all layers in your map have a clear name so that the intended audience of your map will be able to understand what each layer is displaying. When you have finished, save your map document and print out a copy of your map. Close ArcMap. END OF EXERCISE B
Coastal Applications Using ArcGIS Visualizing Population Growth Along the Coast2-41 Exercise B: Analysis and Display of Demographic Data This exercise emphasized the fundamental and important relationship between features and attributes. By joining census data tables to the attribute tables of shapefiles, you are in effect adding additional attribute information to each geographic feature. ArcView contains many different mapping options that allow you to better visualize certain phenomena, such as population density or change. In this exercise you successfully calculated the population change for a geographic area. Next, you learned techniques for classifying population data for better visualization. Finally, you learned some of the many cartographic features in ArcView and used these features to create a map layout. Exercise Summary
Coastal Applications Using ArcGIS Visualizing Population Growth Along the Coast2-42 Exercise B: Analysis and Display of Demographic Data p. 30 Which county has experienced the greatest population change? Does any one state appear to be changing more than the others? Have any county populations decreased? Which one(s)? Middlesex County in Massachusetts experienced the greatest population change. The population change in Middlesex county was much more than any other county (25,000 + more than any other county). At the same time, Newport County in Rhode Island lost 1,761 people between 1990 and p. 32 You have seen how displaying population data differently affects the map. When might you be interested in each of these three parameters: total population; population density; population change? These data might be of interest if you were dealing with resource allocation issues. First, it would be interesting to know which area has the highest population. Then one would be interested in knowing which area has the highest population density. The density of the population is an important factor in allocation of resources for law enforcement, etc. And finally it is important to know where the population is changing so the process can be changed to take this into account. p. 36 What types of data may be better suited for equal interval classification? Census tract identification number (ID #) data. Answers to Exercise Questions
Coastal Applications Using ArcGIS Visualizing Population Growth Along the Coast2-43 Discussion: Overview of Management Applications Which parameters did you choose to include in your map? What other data would you like to have to analyze? ___________________________________________________________________________________
Coastal Applications Using ArcGIS Visualizing Population Growth Along the Coast2-44 You then concentrated on one county (Barnstable, MA) and brought in its census tract and demographic data. You used these data to create a map layout using multiple data frames. Each data frame represented an environmental parameter that you deemed important to coastal managers. Again, you gained experience joining tables and using various classifications and symbology. Most importantly, you learned how all of these skills can and are used in the application of coastal management! In this module, you began by selecting NERRs in New England and then finding the watersheds and counties that influence those NERRs. By doing this you learned how to select features based on where they are in relation to features in other layers. Once you had the counties that made up these influential areas, you found and incorporated the corresponding Census TIGER data. In the process, you learned not only how to find appropriate Census data, but how to join tabular data to your existing shapefiles. From there, you calculated the population change for your counties and used a variety of classification methods to display population information. This taught you how to create and calculate new data fields, as well as helped you become familiar with what classification types work best with different data. Module Summary