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ARCH4050 / ARCH6050 / MUDD6050
GIS / Urban Mapping

Tutorial 2 - Linking External Data & Vector/Raster Conversion

PART A. SETTING UP THE PROJECT

  1. Download the following three datasets by clicking HERE and put them into your working directory in My Documents (remember to unzip and extract them using Windows Explorer):
    • Extent of Water Bodies and Land (sndshore)
    • Metro Transit Revenue Service Routes (tpipath_rev_cur)
    • Metro Transit Route Timepoints (timepoint)
  2. Open ArcMap and add all of the above datasets to a new project.
  3. Adjust the symbologies for easy viewing. Here are some suggestions:
    • For the tpipath_rev_cur dataset, change the symbology to a thin black line;
    • For the sndshore dataset, set the symbology using Categories: Unique Values, using the field feature. This setting will display each sndshore feature differently depending on what its feature value is. To see a list of all of the distinct feature values, click on the Add All Values button. For the feature "waterbody", set the symbology to "Lake" (by double-clicking on the current symbol next to "waterbody"). Lastly, remove the symbologies for "land" and "mudholes" (by right-clicking on each one, in turn, and clicking the Remove Value(s) button) and uncheck the box next to "<all other values>".

PART B. LINKING EXTERNAL DATA

You are now going to import a non-spatial data table into ArcMap. The table is a xls format file (MS Excel) with two columns. The first column lists the time-point key for all of the transit route time points in the Metro bus system. The second column lists the number of routes that use that time point. We are going to use this as an indicator of the level of transit coverage in different areas of the City of Seattle.

Note: I generated this table by a very simple process in SPSS of taking the Metro transit pattern table (available in the Transportation subheading of the King County part of WAGDA) and aggregating it by time-point key, recording the number of rows that have each value of time-point key.

  1. Download a table containing the number of bus routes passing each time point by clicking here.
  2. Add it into your ArcMap project. (select tpfreq$ table)
  3. At the top of the Table of Contents, click on Source tab, you will then see the table you just added in,



  4. Open the table by right-clicking on its name in the Table of Contents and selecting Open.
  5. To get some information on the frequencies listed in this table, right-click on the heading FREQUENC and click on Statistics.



    How many different time points are represented in the table? What are the minimum and maximum values in the field FREQUENC? Write these down so you can include them in your write-up.

    When you're done, click on the X-shaped close box in the upper right corner of the dialog box, then click on the close box for the table itself.

  6. Now you will join this non-spatial table with a spatial dataset, the timepoint dataset, using the unique identifier for the time point as the linking variable. In the Table of Contents, right-click on the name of the timepoint dataset and select Joins and Relates > Join....



  7. In the box that appears, change the following settings:
    • Set the drop-down box under "1." to TIMEPT_ID.
    • Set the drop-down box under "2." to tpfreq$.
    • Set the drop-down box under "3." to KEYTMPT.
    • Click the OK button.



  8. Now change the symbology for the timepoint dataset using the newly attached data. Right-click on the name timepoint in the Table of Contents and select Properties....
  9. Under the Symbology tab, change the type of sumbology to Quantities > Graduated colors. Click on the drop-down box next to Value. In the drop-down box, find and select "FREQUENC". Right-click on one of the symbols and select Properties for All Symbols. In the Symbol Selector dialog box, click on the Edit Symbol... button and uncheck the checkbox next to Use Outline.





    Click OK twice to get back to the Layer Properties. Last, change the number of Classes to "32" and click OK.



  10. Your map will look like this:

PART C. GENERATING A RASTER LAYER FROM POINT DATA

In this step, you will use the Time Points dataset to estimate a surface that represents an abstract quantity we'll call "Transit Route Accessibility". For short, let's call that abstract quantity "TRA". You will do this by creating a raster layer that estimates the TRA value at every grid location, even when there is no Time Point at that location. The procedure you will use does this by interpolating between Time Points in the vicinity of each grid location on the raster dataset.

  1. First, make sure that Spatial Analyst is activated. You can go to Customize menu then select Extensions.., make sure the box next to Spatial Analyst is checked.


  2. Open ArcToolbox by clicking on the icon under the menu.

  3. In the ArcToolbox, click on the small "plus" (+) in front of Spatial Analyst Tools, then Interpolate, and double-click the item IDW (which stands for Inverse Distance Weighted).



  4. In the dialog box that appears, set the following:
    • Set Input Points to timepoint,
    • Set Z value field to tpfreq$.FREQUENC,
    • name your Output raster by clicking on the open folder button, navigating to your personal directory, and giving the new raster dataset a name, such as "TRA".
    • Set the Output cell size to 200
    • Set Power to 2,
    • Set Search radius type to variable,
    • Set Number of points to 4 (and leave blank the Maximum Distance),

  5. Click OK to start the operation. This may take a minute to complete.
  6. The new raster dataset will automatically be inserted into your working project. Double-click on its name to edit the symbology.
  7. Under the Symbology tab, change the Show type to Stretched.
  8. Change the color ramp to one of your liking. I'd suggest the one that has yellow on the left and blue on the right, then clicking on the Invert checkbox to reverse the direction of the color ramp. When you're done, click OK.



  9. Now navigate around the map of Seattle and think about the information that is shown here. Think about and answer the following questions in your write-up:
    • What areas of Seattle seem to have the greatest Transit Route Accessibility?

PART D. CONVERTING A RASTER DATASET TO A VECTOR CONTOUR DATASET

In this part, you will create a vector dataset containing contour lines generated from the raster dataset that you created in Part C.

  1. In the ArcToolbox, Go into the Spatial Analyst Tools again, this time finding the submenu Surface Analysis and thec double-click the item Contour....
  2. In the dialog that appears, set the following:
    • Set Input surface to the name of your raster dataset for Transit Route Accessibility (TRA),
    • Set the Contour Interval to 10,
    • Set the Base Contour to 0, and
    • Set the Z Factor to 1.

    Also name your Output features by clicking on the open folder button, navigating to your personal directory, and giving the new feature dataset a name, such as "TRAcontour".

  3. Click OK to start the operation, which should be completed in very little time.
  4. Now set the symbology for your new contour dataset by double-clicking on its name in the Table of Contents.
  5. Under the Symbology tab, change the Show type to Quantities: Graduate colors.
  6. Under Fields, change the value to CONTOUR. Increase the Number of Classes to 11.
  7. Set the Color Ramp to one you like. I also suggest increasing the widths of the contour lines by right-clicking on any of the symbols and selecting Properties for All Symbols, then increasing the Width to 3.



  8. Click OK to exit the contour dataset's properties.
  9. Now compare the data depicted by the contour map to the data depicted by the raster layer. Think about and answer the following questions in your write-up:
    • How would you compare the results of the contour layer, in comparison with the raster layer?

PART E. REPORTING YOUR FINDINGS

Create two JPEGs showing the City of Seattle, with one showing the raster layer of Transit Route Accessibility (from Part C) and the other showing the contour layer (from Part D). Both maps should also show the tpipath_rev_cur (transit routes) layer, the timepoint (time points) layer, and the SNDSHORE layer to help provide geographical context. You can add other layers as you like to help show the context, but stay away from polygon layers, since it will be difficult to show both the raster layer and a polygon layer at the same time.

Just to recap, your write-up should include the following, all in a Microsoft Word file:

  • A JPEG showing the raster layer of Transit Route Accessibility in City of Seattle,
  • A JPEG showing the contour layer in City of Seattle,
  • Answers to the questions in Part B, Step 5,
  • Answers to the questions in Part C, Step 9,
  • Answers to the questions in Part D, Step 9.

Note: In terms of suggested length, I am only expecting one or two sentences for each of the discussion questions.

The deliverable:
The assignment is due on Feb 16, 9:30am. Turn it in to Moodle.

prepared by Ming-Chun Lee, 02/04/2015