[Talk-us] what do we mean by geocoding?

[Carl Anderson]

Steve,

On a more technical level "ZIP Code Tabulation Areas" (ZCTA5) are
statistical areas that are built using a predominant ZIP Code method.
The predominant ZIP Code for addresses within a Face (Faces combine into
Blocks) is assigned to the Face.  Then a complex algorithm in-fills ZCTA5
information onto Faces and Blocks that do not have a ZCTA5 from adjacent
and nearby Faces and Blocks.

Part of the reason that the USPS disavows a geographic boundary for ZIP
Codes is that they often keep residential delivery and commercial delivery
and high-rise delivery (having apts or suites) separate even when they are
next to each other on the street.  This can be confusing if you assume a
geographic basis for ZIP Codes.

Carl.


On Tue, Jun 25, 2013 at 4:05 PM, Steven Johnson <sejohnson8 at gmail.com>wrote:

> On Sun, Jun 23, 2013 at 1:12 PM, Bryce Nesbitt <bryce2 at obviously.com>wrote:
>
>>
>> At SOTM-US (State of the Map US) I spoke to Steven Johnson of the Census
>> Bureau on the issue of what data USPS actually has internally (as the
>> Census Bureau has some special licensed access to this data).
>>
>> Yes, just to amplify: the Census Bureau purchases the Delivery Sequence
> File (DSF) from USPS on an ongoing basis (at least 2x/year). The use of the
> DSF dates from 1994 and Congressional authorization was required for the
> Bureau to use the DSF. The DSF served as the foundation for the Bureau's
> Master Address File (MAF). The DSF is by far the largest source of address
> data for the Bureau, in excess of 90%.
>
> Apparently, the USPS does not even know the geocoordinates of most of
>> their assets (e.g. post boxes, post offices, delivery addresses).  They do
>> have a near perfect database of *what* these assets are, just not
>> the coordinates.  And that itself is useful.  Knowing a postbox exists is a
>> huge clue to geocoding it.  Knowing a postbox has been removed from service
>> is a huge clue.
>>
>
> Actually, I think I was referring to ZIP codes (but you're forgiven for
> not recalling the details. ;-) ). The USPS *does not* maintain ZIP codes as
> polygon features, because the ZIP code is associated with a delivery
> *point* (i.e. a postal address). The Census Bureau combines those into
> something known as "ZIP Code Tabulation Areas", which are an approximation
> created by drawing boundaries around a collection of *points* that have ZIP
> code in common. Many other commercial vendors create something similar. But
> there is no official database of ZIP code polygons.
>
> As to whether USPS has coordinates/geocoded coords for all of the postal
> 'furniture' out there, that I don't know.
>
> -- SEJ
> -- twitter: @geomantic
> -- skype: sejohnson8
>
> There are two types of people in the world. Those that can extrapolate
> from incomplete data.
>
>
>
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