Intermediate GIS Skills Using Intermediate GIS Skills Using ESRI's ArcGIS Software ESRI's ArcGIS ...

14 Pages·2009·1.38 MB·English

Intermediate_GIS_Skills_With_Arcgis_931.Doc Page 1 of 14

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In this exercise you are introduced to the ArcMap interface and some of the basic skills necessary to begin
exploring geospatial data and create simple maps. Once you have successfully completed this part of the
tutorial, you should know:

• How to use the Union Tool to combine to • How to create Summary Statistics tables
feature data sets from datasets
• How to create new fields in a feature • How to Geocode tables of street addresses
dataset or table • How to create a distance raster to measure
• How to calculate the geometric attributes of distance for a feature dataset
a feature • How to extract raster values to a point
• How to calculate attribute values across feature dataset
feature attribute fields • How to aggregate point features to counts
• How to Join datasets based on attribute in a polygon dataset
values • How to set Relative Pathnames to make
• How to Join datasets based upon location your GIS Projects more portable

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The datasets used in this tutorial are available for download on the Map Collection Website. Feel free to
download and use these tutorial materials, as you wish, and to pass them along to interested colleagues.

Go To the Map Collection Homepage (www.library.yale.edu/maps) in your Web Browser.

Under the Quick Links Section on the right, Click on the “Download GIS Workshop Materials” link.

Find the “Data” Link for the ArcGIS 9.3.1 “Intermediate GIS Skills Using ESRI’s ArcGIS Software” and
Right-Click on the Link.

In Firefox, Select “Save Link As,” in Internet Explorer, Select “Save Target As…”

Depending on your browser and setup, you may be offered a Browse Window, to select the folder into
which you want the downloaded file placed. If so, Browse to a Folder on your hard drive that you have
write permission for. For this tutorial, we will assume that you are using the C:\temp folder of the machine
you are working on.

Save the Downloaded File to the C:\Temp Folder.
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You should now have a file called “Intermediate_GIS_Skills.zip” in your new folder. It is now necessary to
decompress, or unzip, the tutorial data for use. Note that in Microsoft Windows XP and Vista, it is possible
to “Explore” a compressed file, as if it were a folder. ArcMap does not support this type of browsing, so it is
The Yale Map Collection Stacey Maples – GIS Assistant
At Sterling Memorial Library 203-432-8269 / [email protected]
130 Wall Street, Room 707 www.library.yale.edu/maps
Intermediate_GIS_Skills_With_Arcgis_931.Doc Page 2 of 14

necessary to actually unzip the file for use. This part of the tutorial assumes that you are using Windows’
built in Compressed File support.

1. Browse into the Folder where you saved the
Intermediate_GIS_Skills.zip file.

2. Right-Click on the File and Select “Extract All…”

3. Click Next to arrive at the window shown at the right.

4. Click Next to Extract the File.

5. When finished, browse to the
C:\temp\Intermediate_GIS_Skills\ and double-click
on the Intermediate_GIS_Skills.mxd Map Document
file to open it.

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In this tutorial, we will be performing what is referred to as “Areal Interpolation” of Census Attributes. We
have a set of boundaries (in this case the Major Watershed Basins of Connecticut, our CT_Major_Basins
Layer) for which we would like to summarize the population. Our
problem is that these watershed boundaries do not correspond with
the geographic units that the U.S. Census uses to collect and tabulate
demographic data. Some of the Census Block Groups in our
CT_Block_Groups layer overlaps more than one Watershed basin
unit. What we will do in the following steps is calculate the proportion
of overlap for each Census Block Group, relative to the Watershed
Boundaries, and use these proportions to assign an appropriate
estimate of the population to each watershed.
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First, we need to determine the initial
area of each of our “intact” Census
Block Groups. We can refer to these
as the “Parent” features.

1. Right-Click on the
CT_Block_Group Layer and
Open the Attribute Table.

The Yale Map Collection Stacey Maples – GIS Assistant
At Sterling Memorial Library 203-432-8269 / [email protected]
130 Wall Street, Room 707 www.library.yale.edu/maps
Intermediate_GIS_Skills_With_Arcgis_931.Doc Page 3 of 14

2. Take a few seconds to examine the data available in this dataset. This data describes the
demographic characteristics of every Census Block Group in our area of interest.

3. Click the Options Button at the Bottom of the Attribute Table and Select Add Field...

4. Add a Field with Name = AREA, and Type = Float.

5. Click OK.

6. Scroll to the far right of the Attribute Table to
view the newly added AREA Field.

7. Right-Click on the Area Field Header and Select
Calculate Geometry… Click Yes when warned
about “Calculating Outside and Edit Session.”

8. Change the Units to Square Miles US [sq mi].

9. Click OK.

10. Note that the AREA Field should now be
populated with the new values.

11. Close the Attribute Table
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Now, we need to merge the Block Group and Watershed boundary files, so that those Block Groups that
span more than one watershed will be split into their sub-units of overlap, or “child” features. To do this, we
will use a technique generically referred to as “Geoprocessing.” Geoprocessing is the act of applying any
number of spatially transforming tools to a dataset. In this case, we will use
the Union Tool to create a new dataset.

12. Open the ArcToolbox using the ArcToolbox Button on the
Standard Toolbar.

13. Click on the Search Tab, at the bottom of the ArcToolbox Panel.

14. Enter “union” as your search term and click Search.

15. Double-Click on the Union Tool, from the Analysis Tools Toolbox.

16. Select the CT_Major_Basins and CT_Block_Groups Layers as the
Input Features.

The Yale Map Collection Stacey Maples – GIS Assistant
At Sterling Memorial Library 203-432-8269 / [email protected]
130 Wall Street, Room 707 www.library.yale.edu/maps
Intermediate_GIS_Skills_With_Arcgis_931.Doc Page 4 of 14

17. Click on the Show Help>> Button at the bottom of the Dialog Box and note that the Help System is
Context-Sensitive.

18. Save the Output Feature Class
to your
C:\temp\Intermediate_GIS_Skill
s\CT_Watershed_Data.gdb
and name it “Union”

19. Leave the remaining options at
their default settings.

20. Click OK to Apply the Union
Tool.

21. Click Close once the process
has completed.

22. You should be left with a new
Union Layer, at the top of your
Table of Contents.
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Now we need to calculate the NEW AREA of those “Child” Block
Groups that were split by the Union Process and then the proportion
of their original AREA.

23. Right-Click on the Union Layer and Open the
Attribute Table.

24. Click on the Options Button and Select Add Field…

25. Add a new field: Name = SUBAREA, Type = Float.
Click OK.

26. Click on the Options Button and Select Add Field…

27. Add a new field: Name = WEIGHT, Type = Float.
Click OK.

28. Click on the Options Button and Select Add Field…

29. Add a new field: Name = WTPOP, Type = Short
Integer. Click OK.

The Yale Map Collection Stacey Maples – GIS Assistant
At Sterling Memorial Library 203-432-8269 / [email protected]
130 Wall Street, Room 707 www.library.yale.edu/maps
Intermediate_GIS_Skills_With_Arcgis_931.Doc Page 5 of 14

30. Scroll to the right of the Attribute Table to find the newly added SUBAREA Field.

31. Right-Click on the SUBAREA field header and Select Calculate Geometry…

32. Change the Units to Square Miles US [sq mi].

33. Click OK to apply the calculation.

Now we will calculate the proportion of the child area to parent area, which will be used as a weight to apply
to the demographics we are interested in. First, we must exclude those polygons that have an AREA=’0’
(these are coastal “slivers” and are not important to the results of our analysis).

34. Click on the Options Button and Select “Select by Attributes…”

35. In the Query Argument panel, at the bottom of
the Select by Attributes Dialog Box, enter the
query:

"AREA" <>0
36.
37. This will select only those records that do not
have an AREA = 0.

38. Click on the Verify Button to check your SQL
Query Syntax.

39. Click Apply.

40. Click Close.

41. Right-Click on the WEIGHT field header and
Select Field Calculator…

42. Use the Field Calculator to build the following
argument:

[SUBAREA] / [AREA]

43. Click OK to apply the calculation and note that,
because you have an active select, the calculation is
only applied to the selected subset of records, thus
avoiding a “divide by 0 error.”

44. Finally, Scroll to the far right of the Attribute Table,
Right-Click on the WTPOP field header and select
Field Calculator…

The Yale Map Collection Stacey Maples – GIS Assistant
At Sterling Memorial Library 203-432-8269 / [email protected]
130 Wall Street, Room 707 www.library.yale.edu/maps
Intermediate_GIS_Skills_With_Arcgis_931.Doc Page 6 of 14

45. Use the Field Calculator to build the following argument:

[POP2004] * [WEIGHT]

46. Click OK to apply the Calculation.

47. Save your work.
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Now that we have a set of
Census Boundary files that
correspond to the watershed,
and estimates of the population
of those new boundary units, we
need to summarize those
population estimates for each of
our watershed units.

48. On the Attribute Table
Click the Options Button
and select Clear
Selection.

49. Close the Attribute Table.

50. Return to the ArcToolbox
Search Tab, enter
“summary” as the search
term and click Search.

51. Double-Click on the Summary Statistics
Tool.

52. Select the Union Layer as the Input
Table.

53. Browse to the
C:\temp\Intermediate_GIS_Skills\CT_
Watershed_Data.gdb and save the
Output Table as
“Population_Summary”

54. Select WTPOP as the Statistics Field,
and select SUM as the Statistic Type.

The Yale Map Collection Stacey Maples – GIS Assistant
At Sterling Memorial Library 203-432-8269 / [email protected]
130 Wall Street, Room 707 www.library.yale.edu/maps
Intermediate_GIS_Skills_With_Arcgis_931.Doc Page 7 of 14

55. Select MAJOR as the Case field.

56. Click OK.

57. Click Close when the tool completes.

58. Click on the Source Tab, at the Bottom of the Table of Contents.

59. Right-Click on the Population _Summary Table and Open it to observe the population counts for the
watersheds.

60. Close Attribute Table.

61. Save your work.

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Ultimately, what we want is a CT_Major_Basins
Layer with the Population value as an attribute
of each feature. This is achieved through the
use of a table-to-table join.

62. Right-Click on the CT_Major_Basins
Layer and Select Joins and
Relates>Join…

63. Set the Options as shown in the image
to the right:

64. Click OK.

65. Right-Click the CT_Major_Basins Layer
and open its attribute table. Note that
the population counts have now been
joined to the boundary file.
The Yale Map Collection Stacey Maples – GIS Assistant
At Sterling Memorial Library 203-432-8269 / [email protected]
130 Wall Street, Room 707 www.library.yale.edu/maps
Intermediate_GIS_Skills_With_Arcgis_931.Doc Page 8 of 14

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1. Right-Click on the CT_Streets Layer
and Open the Attribute Table.

Note the fields included in this
reference data set. This streets
reference data is ‘topologically
integrated,’ meaning that there is
information encoded into the
dataset. Fields included for each
street segment that are essential to the
geocoding process include:

• FNODE – This is an identifying number for the point FROM WHICH the street segment
begins.
• TNODE – This is an identifying number for the point TO WHICH the street segment
extends.
• FRADDL & FRADDR – These are the values of the address range for the given street
segment at the FNODE for the LEFT & RIGHT side of the street, respectively.
• TOADDL & TOADDR - These are the values of the address range for the given street
segment at the TNODE for the LEFT & RIGHT side of the street, respectively.

Together, the FRADDL, FRADDR, TOADDL & TOADDR values provide the numeric range of
addresses for both sides of a given street segment. This information is used to calculate the
“percent along” the street segment that a given address lays.

2. Close the CT_Streets table.
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3. If you are not still in the Source Tab of the Table of Contents, click on it.

4. Right-Click the
CT_TRI_Facilities table
and Open it.

Note that this table contains data
about facilities cataloged and
reported in the Toxic Relief
Inventory. The FStreet and other
fields prefixed with “F” are
attributes of the facility locations.
We will use these address
The Yale Map Collection Stacey Maples – GIS Assistant
At Sterling Memorial Library 203-432-8269 / [email protected]
130 Wall Street, Room 707 www.library.yale.edu/maps
Intermediate_GIS_Skills_With_Arcgis_931.Doc Page 9 of 14

attributes to create an explicitly spatial dataset from a dataset with ‘implicit’ spatial data (street addresses).
Note also that the format of the addresses in the table differs from that in the reference street data. This
format, where the full street address is concatenated into a single field is how ArcGIS “prefers” address data.

5. Close the CT_TRI_Facilities table.
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The Address Locator is an indexing device that “connects” your street reference data to your address data
by mapping the appropriate fields in each dataset to one another. The Address Locator also allows you to
“encapsulate” specific settings for how the data should be geocoded, so that you can provide an optimized
solution for repeatable geocoding of data.

6. Click on the
ArcCatalog Icon to
Open ArcCatalog.

7. In the Catalog Tree, at
the left of the
ArcCatalog application,
Browse to the
C:\temp\Intermediate_
GIS_Skills\CT_Waters
hed_Data.gdb
database and find the
CT_Address_Locator
file.

8. Right-Click on the
CT_Address_Locator
and open it’s
Properties.

9. Note the mapping ot the attributes from
the CT_Streets reference dataset to the
necessary geocoding fields.

10. Note, also, that many of the setting can
be changed in this dialogue.

11. Click Cancel to close the Address
Locator Dialog.

12. Minimize ArcCatalog and return to ArcMap.

The Yale Map Collection Stacey Maples – GIS Assistant
At Sterling Memorial Library 203-432-8269 / [email protected]
130 Wall Street, Room 707 www.library.yale.edu/maps
Intermediate_GIS_Skills_With_Arcgis_931.Doc Page 10 of 14

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1. In the Source Tab of the Table of Contents, right-click on
the CT_TRI_Facilities table and select Geocode
Addresses…

2. Click Add and Browse to the
C:\temp\Intermediate_GIS_Skills\CT_Watershed_Data.g
db\CT_Address_Locator.

3. Click Add.

4. Click OK.

5. For the Address Input Fields, map the appropriate
fields as shown on the right:

6. For the Output Feature Class, suffix the default
value with “_01” so that it becomes
D:\Patrons_and_Projects\Stacey.Maples\Worksh
ops\2009 Workshops\02 - Intermediate GIS
Skills\Base\CT_Watershed_Data.gdb\Geocoding
_Result_01.

7. Click OK.

8. When the “Geocoding Addresses…” Status Window
finishes, click Rematch.

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1. In the Interactive Rematch Dialog Box, right-click on
the Status Field header and select “Sort
Descending.” This will place all Unmatched records at
the top of the table.

2. Click in one of the cells for the first records to highlight
it.

3. Note the available Candidates in the lower panel.
Compare the values for these candidates to those of
your unmatched record.

4. Select the first candidate and click on the Match button.
The Yale Map Collection Stacey Maples – GIS Assistant
At Sterling Memorial Library 203-432-8269 / [email protected]
130 Wall Street, Room 707 www.library.yale.edu/maps