GUS 0262: Fundamentals of GIS Spring 2007
Due April 10
Lab 6: Vector Operations, Part 2
Purpose of the lab: To introduce data acquisition from the WWW and to reinforce skills in relational data model and vector analysis operations.
1. Download Tabular Census Data
Instead of using data on the shared drive, we will acquire data from sources available through the WWW. We will first acquire U.S Census tabular (attribute) data from American Factfinder.
Open Internet Explorer and go to www.census.gov.
Click the link on the left for ‘American Factfinder’.
Click the link on the left for ‘Data Sets’.
Click the radio button ‘Census 2000 Summary File 3 (SF 3) - Sample Data’.
Under ‘Select from the following’ click the link on the right for ‘Custom Table’
At the top of the page choose the tab ‘geo within geo’.
Under ‘Show me all’ select ‘Block Groups’ .
Under ‘Within’ select ‘County’.
Under ‘Select a State’ select ‘Pennsylvania’ .
Under ‘Select a County’ select ‘Philadelphia’.
Under ‘Select one or more geographic areas and click add’ select ‘All Block Groups’ and click ‘Add’.
Press ‘Next’.
Under ‘Select a table and click ‘Go’ select ‘P1. Total Population’ and click ‘Go’.
Check the box next to ‘Total’ and press ‘Add’.
Under ‘Select a table and click ‘Go’ select ‘P53. Median Household Income in 1999 (Dollars)’ and click ‘Go’.
Check the box next to ‘Median Household Income in 1999’ and press ‘Add’.
Under ‘Select a table and click ‘Go’, scroll to the bottom of the list and select ‘G001. GEOGRAPHIC IDENTIFIERS’ and click ‘Go’.
Check the box next to ‘State (FIPS)’, ‘County’, ‘Census Tract’, and ‘Block Group’ and press ‘Add’.
Check all six variables you have added to the bottom box and Press ‘Next’.
Click ‘Show Result’.
On the top, right side of the screen go to the Print/Download drop down menu and choose Download.
Press OK.
(If the pop-up/download blocker appears, be sure to accept the pop-up/download. Also, it occasionally takes a few tries at the download for the Open/Save option dialog box to appear. So keep trying.)
Save the zipped Excel file to your workspace.
Extract the file to your workspace.
Open the Excel file ‘ct_dec_2000_sf3_u_data1.xls’ in Excel.
Delete the entire second row (not the column, the row!). Click on any one cell within the table.
Did you click on any one cell within the table yet? If yes, proceed…
Go to File->Save As and for Save as type choose ‘DBF 4 (dBASE IV) (*.dbf)’.
Save the new file in your workspace using the file name ‘phbg_sf3.dbf’.
Close Excel.
Open ArcCatalog and view the new table.
2. Download Census Cartographic Boundary Files
Now that we have acquired the Census tabular block group data we will acquire the block group boundary files.
Open Internet Explorer and go to www.geographynetwork.com.
Under ‘Featured Content’->’Data’ click on ‘Census Tiger/2000’.
In the new pop-up window, read the information, scroll to the bottom of the page and click on ‘Link to Content’.
In the new pop-up window, click on ‘Free Download’->‘Preview and Download’.
Select Pennsylvania and press ‘Submit Selection’.
Under ‘Select a Layer’ choose ‘Block Groups 2000’ and press ‘Submit Selection’.
In the new pop-up window, check the box next to ‘Philadelphia’ and click ‘Proceed to Download’.
Press ‘Download File’ and save the file to your workspace.
Extract the zipped file, which produces another zipped file named ‘grp0042101.zip’.
Unzip this file, which produces a shapefile.
View this new shapefile in ArcCatalog.
3. Join the Spatial and Attribute Data
Open ArcMap and add the table and the shapefile. Open the attribute table for the shapefile and the standalone attribute table. We would like to join the phbg_sf3.dbf file onto the shapefile attribute table but there is no obvious field to use for the join!
Notice in the shapefile table the field STFID. This field contains identifiers for the state (1st and 2nd digits), county (3rd-5th digits), tract (6th-11th digits), and block group (12th digit). The phbg_sf3.dbf table has the same information, but broken up into separate fields.
Open the phbg_sf3.dbf table and add a new field named ‘mystfid’. Make the new field a text type.
Calculate the value of the new field as ‘[STATE] + [COUNTY] + [TRACT] + [BLKGRP]’.
This will produce a value that is the value of all those fields appended onto one another.
Now join the phbg_sf3.dbf table onto the shapefile attribute table using the fields ‘STFID’ and ‘mystfid’, respectively.
4. Compare Block Group and Tract Data
Make a choropleth map of median household income by block group. Note that the field names are in the Census summary file format. You can use the sf1.pdf and sf3.pdb documents under S:/GUS_0262/Tiger to interpret the field names. Median household income is P053001.
Add the tracts shapefile to ArcMap from the S:/GUS_0262/Tiger folder . Set the color of the tracts layer to hollow and increase the thickness of the outline width to 2 or 3 points.
Move the tracts layer above the block groups layer in the table of contents so that you can see the tracts boundaries on top of the block groups.
Do you see a lot of variation in median household income within individual tracts?
ASSIGNMENT
Objective
The objective of this assignment is to identify an area in which to build a new ‘gourmet’ food market in the city of Philadelphia. The market must be:
1. within a Census 2000 block group having a median household income value in the top 10% of all block groups containing population.
2. within a Census 2000 tract with a population density in the top 10% for all tracts containing population.
3. in a contiguous region with an area of at least 110,000 square meters
Deliverables
Turn in a report addressing this objective. This report should include a map of the potential area(s) in which to build the market. A second map should be used to illuminate your methodology.
Getting Started
1. Acquire the block level population data from the census web site, join it to the block group shapefile table, select those block groups with population, and export the selected block groups to a new shapefile.
2. Join the median income data table onto the new shapefile table and select those block groups in the top tenth percentile in median household income (hint: use the quantile class break scheme to determine the median household income value to use in your query). Export the selected block groups to a new shapefile.
3. Copy the tracts shapefile from S:/GUS_0262/Tiger. Select those tracts in Philadelphia (with a FIPSSTCO field value = 42101) and export those tracts to a new shapefile.
4. In the new shapefile, create a new field and encode the population density (this shapefile has all the information you need to do this).
5. Select those tracts with population. Of those selected tracts, select those tracts in the top tenth percentile in population density. Export the selected tracts to a new shapefile.
6. Convert both the top 10% median household income block group and top 10% population density tract shapefiles to UTM and bring the UTM versions of the shapefiles into ArcMap.
7. Use an intersect operation to find the area common to your top 10% block group and tracts layers.
8. Perform a dissolve operation on the resulting shapefile.
9. Using the shapefile output from the dissolve, generate a new shapefile in which each polygon is encoded as an individual record in the attribute table.
10. Encode the area of each new polygon in a new field.
11. Select those polygons that meet the area criteria and export them to a new shapefile.
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