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Lesson 4
Project 4: Address Geocoding |
| For this lesson we have been asked to first analyze
the soil and rock composition of a geographic area to determine where Radon
is most likely to occur. This is then overlaid with the a map of the
roads in the geographic area, to which we geocoded a series of addresses
creating a map of homes that are at risk. |
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Figure 1 shows a map of the underlying
soil composition overlaid with a road layer.
Figure 1: Soil Layer of
Geographic Region with Road Layer
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| Figure 2 shows this same area, this time with the
rock substructure, also overlaid with a road layer.
Figure 2: Rock Layer of
Geographic Region with Road Layer
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| When the attributes of these two layers are combined
according to a Radon potential algorithm, a map of 'at risk' potential Radon
sites results. This is shown in Figure 3.
Figure 3: Radon Potential Areas |
| The next step was to add the geocoded addresses for
all homes that have submitted Radon testing kits. Figure 4 shows the
map of the addition of these geocoded addresses.
Figure 4: Map of Homes Submitting
Radon Testing Kits
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| As a part of this effort, several addresses needed to
be corrected and/or updated. The process of updating these records,
while relatively easy in the context of this exercise because the
corrections were already known, can be quite difficult in practice.
Field verification visits may be necessary to actually "eyeball" the address
in question, and updating this kind of database can become quite time
consuming and expensive. In fact, the address for one of my clients is
incorrectly located in all the major commercial mapping software
applications including MapQuest, Microsoft's Streets and Trips, and even in
my automobile's onboard mapping/GPS application. Given that all three
applications are incorrect, and yet incorrect identically in that they all
put the facility in exactly the same, but wrong, location, I would suspect
that the base information from which all three applications were derived is
incorrect. This leads one to an interesting question, how does one
provide feedback to the various mapping application vendors so that their
product can be updated, or does the vendor rely instead on the Census
Bureau's TIGER file updates instead? In the
final part of this exercise, we were asked to find and identify a specific
addresses. Using the FIND tool, we were given a specific address and
asked to note it on our Radon potential area map. Figure 5 shows the
address to be found in the lower left area of the map identified by a circle
with a star in it. While, the FIND tool does allow the item to
'flash', unless one is using an animated GIF file, this is a little
difficult to show statically.
Figure 5: Finding a Specific
Address
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Try This
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| For the Try This segment of the lesson, we were asked
to download a file of six addresses and "append" this list to the list of
addresses already geocoded. However, before this could happen, one of
the addresses had to be corrected as we were told that the zip code was
entered incorrectly. In order to find the correct zip code, I went
back the Roads layer and pulled up the underlying database. Sorting on
the name of the roads, I found the road name for the record in question and
in that record found the correct zip code. I then went back and
updated the TryThis address database file to get six fully geocoded
addresses. This was then appended to the previous set of address, and
the corresponding maps updated. Figure 6 shows the six new addresses
added to the map as a separate layer.
Figure 6: Six New Address
(Starred Items) Added to the Map
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| Next, the six addresses from the TryThis download are
added to the previously geocoded addresses of the Radon exercise.
Figure 7 shows the two attribute files after the append has been made.
Note that the same six addresses in the "Geocoding_Result_TryThis" table are
the same as the last six, and highlighted, entries in the "Geocoding_Result"
attribute table.
Figure 7: Comparison of New
Address Attribute Data After Append Command
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| Finally, with the six addresses highlighted in the "Geocoding_Result"
attribute table, they are also highlighted in the Geocoding_Result layer as
the light blue circles. With the "Geocoding_Result_TryThis" layer
still active, you can just see the tips of the stars peeking out from under
the blue circles, indicating that these addresses are in both layers and
both attribute tables. If further work is to be performed using all
the address of homes responding with Radon test kits, then only the "Geocoding_Result"
layer need be used as this layer contains the complete list of all homes
that have responded to the Radon survey.
Figure 8: Updated Map Showing
Locations of Newly Added Addresses |