Frank's Catering

Find all Zip+4 Zip Codes® Within 1 Mile of Frank's Catering Locations in Reno Using TIGER/Line® Data - Frank's catering has 3 kitchen/service locations within the Reno, NV, metropolitan area.  Frank wants to spam all businesses within one mile of each location to promote a new "walk-in" box lunch program.  He wants to use his kitchen capacity to capture some of the lunch-hour trade.  Frank figures that people won't go more than a mile even for one of Frank's killer values on gourmet box lunches so he  prefers to mail only those businesses within one mile.  Frank wants Zip+4 accuracy but he only has a few locations and doesn't want to spend a lot of time learning a mailing program.   Plus, he's really cheap and loves the idea of solving his problem with a $145 program and free data.

In TIGER/Line, Zip codes are data attributes that are associated with line segments defining streets.  Each street is chopped up into one or more line segments that have associated with each segment the start and stop addresses and Zip codes for the left and right side of the street.  Frank's task is equivalent to picking out all of the street line segments that fall within one mile of his facilities.

1. Prepare a Base Map of Reno - This is covered in step-by-step detail in a separate case study.   This case study assumes you have already prepared a base map of Reno from TIGER/Line files and have converted it to a projected map.  Format the map to taste.  We like to format road lines as a dark gray, but that's a matter of personal taste. Save the workspace under some name.  This will update changes to the map.

2. Insert Frank's Catering Locations - From the Layers menu, insert a new blank layer and call it Stores.  Frank has three locations.  Insert these as points using the Create Point tool at the right locations.  For a small number of locations this is easiest to do just by eye with the map Zoomed in.   For a large number of locations taken from a geocoded file, one would import a text or Access file listing the names of each store using techniques (such as Import Data from ODBC source within Table View, or the Merge Data tool) that are not covered in this case study.  Format these points so that they are visible.  We used a size of 3, a foreground color of black (the circumference of the point circle), and a background color of bright green (the fill color).  We retained the default point icon, a round circle.

3. Create 1 Mile Buffer Zones - Use the Buffer Zone (Points Only) solver to create three buffer zones. The Buffer Zone solver draws buffer zones around specified map objects. The Points Only version of this solver uses an especially fast algorithm to draw buffer zones when all of the specified map objects are points.   The point set to be used to create the buffer zones is Stores (which contains three points).   We've set up the solver to draw a buffer zone in a radius of one mile around each point in the set using an accuracy factor of 50 to make the resultant buffer zone seem "smooth".   The thumbnail shows the popup dialog that appears when this solver is run.

4. Save the Selection to a New Layer - The output of the Buffer Zones solver is three circular areas surrounded by three circular border lines.  By default, the output is also the new Selection.   Click on the Move to New Layer button to move the Selection (ie, the three buffer zones) to a new layer called 1mi_buffer.    Note that the Buffer Zones solver creates the new areas/lines using Black for Foreground and Background, with a rather inelegant area style.  The new areas are drawn in the active layer.  By moving them to a new layer called 1mi_buffer, the new layer is created over top of all other layers.  This is done deliberately to assure that the newly-created objects are visible even in very complex maps.  It is assumed that the user will wish to move the new objects to some final desired position in the layer display stack.

5. Move the Buffer Zones Layer - Using the mouse, drag the 1mi_buffer layer to the right of the Reno_tiger_o layer so that all the other layers are visible above the buffer zones.

Notice how the road network and the Stores layers appear "above" the buffer zone.  This is another practical reason to format roads as dark gray instead of pure black, since the dark gray will be visible above black areas as well as on light areas.

6. Reformat the Buffer Zones to a Pretty Color -  While not strictly required for analysis, it takes only a moment to change color or style to keep one's maps looking good.  Click on the 1mi_buffer layer tab to make it active (ie, white colored) if it is not, and then simply click on the foreground color well in the Formatting toolbar to change the color.  We picked a nice teal green.  For the rest of this case study, we will also Zoom into the map to show greater detail.

7.  Select all Roads inside the Buffer Zone - Using the SQL toolbar (as above) , we will select all of the lines in the Reno_tiger_o layer ( which are roads marked with Zip+4 codes) that are contained by the buffer zone.   Set up the toolbar with a) Reno_tiger_o in the left pull down box (the pull-down menu gives you a choice of layers or other sets to pick), b) Containing (see note below) in the middle box and c) the ID of the Buffer Zone in the right box.   The ID is easily selected by first clicking on the Object Selector button and then clicking on the desired Buffer Zone - this will automatically load the object ID in the right box.  We use this system to enable formulas to be written into the right box.   By the way, the little blank box to the left of "containing" if pushed in becomes a "not" box, to create constructions such as "not containing" or "not within".Note: Due to an error, R4 has shipped with "containing" and "contained by" verbs switched in the spatial analysis.  A service pack will correct this error and will substitute the word within for "contained by". 

8. Repeat for the other two Buffer Zone areas - The SQL toolbar is set up to do spatial analysis based on one defining value (an object, in this case)  at a time, unless formulas are used.   As the illustration shows, only the lines within the buffer zone indicated with the Object Selector button will be selected.  To get the roads in all of the three buffer zones we have drawn, it is easiest to simply repeat the above procedure for each of the three Buffer Zones using Add to Selection solver selection mode (illustrated at left).  Because this only takes two mouse clicks, it is very fast and easy to do even for a dozen such zones. 

For the purpose of this case study, we will use a slightly different procedure for the second buffer zone, the one below and to the right of the zone used in step 7 above.   In step 7, we used the containing operator (or, with the upcoming service pack, the within operator), which selects all objects every part of which is inside the defining area.   Because TIGER/Line attaches Zip Codes to line segments that might be of considerable length, if Frank searches only for those line segments that are entirely contained within a buffer zone, he might miss a few street segments that are long enough to be partially inside the buffer zone and partially outside. 

To deal with this situation, Frank can use the touching operator, which will select all segments any part of which is inside the buffer zone or touching its perimeter. The result (at left)  is to select some road segments that can be seen to extend past the edges of the buffer zone.  No big deal... Frank would rather be sure he is getting all the segments inside the buffer zone.  Note that close inspection of the edges of the buffer zone used in step 7 (seen partially in the illustration at left) shows that some of the smaller segments near the edge were not selected because they were not fully within the buffer zone.

9.  Save the Results to a Layer and Inspect with Table View -  The job is basically already done.   All we have left is some housekeeping and reporting.  We'll first save the selected lines to a new layer called Results.  We can inspect the results by clicking open Table View.  Click on the thumbnail at right to see the sample data set in Table View.  This Table View has been slightly "prettified" by arranging the order of fields and moving the column widths about.  We've also clicked on the Zip Code column heads to sort them.  Not all the road segments selected have Zip Codes in them.  By sorting the columns by zip, it's easy to see which do, and then to highlight them for exporting by ODBC.  

10. Export the Results using ODBC -  First, we need to highlight only those records with Zip codes.  Click on the Zip code column headers to sort by Zip code.   That will put all the records without any zip codes down at the bottom. Scroll through table view until you get to the empty records section.  Right mouse click on the last record with a zip code to highlight it.  Scroll back up to the beginning of Table View and Shift-Click on the first record.  That will highlight all the records with Zip Codes.  Now, click on the Export button and in the resulting ODBC dialog pick the destination of your choice.  Note: of course, there are lots of other ways to pick out only those records with zip codes besides the manual highlighting technique used above.  One can think of about a hundred ways to do it using SQL toolbar and various combinations of Intersect selection, etc.  But for such a simple problem, why think?  It's easier on mental capacity to do it visually by highlighting within Table View.

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