A Question About Zip Codes

[+Two Left Knees]

When I type in our zip code, I see at the top of the page a place called Bottle Creek. Bottle Creek is many miles from us, up in the hills and is just that, a creek. There are no houses, much less a Post Office. We're planning a trip and I've noticed the same thing when I enter other zip codes; they show entirely different towns. How can we know if the zip codes are giving us an accurate location and why does the zip code show an area without a post office?

[+Muirwoody]

It is probably showing you caches out from a radius from the zip you entered, including zip codes farther out.

[+cache_us_if_you_can]

How can we know if the zip codes are giving us an accurate location...

The zip code search starts at the geographic center of the code. Many times this is not near a specific site. You can do a more specific search by entering the Long & Lat.

...and why does the zip code show an area without a post office?

I'm not sure if every zip code has it's own post office, but I think that sometimes rural zips share a centralized office.

[+SixDogTeam]

Rural zips have their own office, but that office may provide box service only, no home delivery. So the home delivery address zipcode for that area will be a neighboring office...so your mail address is a different town than the town you physically live in, even tho your town has its own post office.

[+Brianslost]

You might do better getting the caches by inputting your home coordinates rather than the zip code.

[+Robespierre]

44833, our zip, shows a small place where an ex-President was born. What, I think, happened, in history, is that in many places the local Postmaster assigned names for places, and zip code jurisdictions. It really doesn't affect your geocaching - except and unless you live in a very very sparsely populated area. Then it could be quite a few miles off, but what's a few miles in Montana?

[Keystone]

Have a look at this discussion topic from earlier this month on the same subject, and the older thread that is "Markwelled" from inside that one. You'll see that zip codes are an inexact science. They were designed for identifying mail delivery routes (often, a linear concept) rather than providing precise locations, like the spatial concept of latitude and longitude. If you need precision, use coordinates for the center point of your search radius. Regard zip codes as a general approximation of the right area.

[+Mr Smiles]

If I learned what I think I learned, then what I learned might help you.

 

(1) A ZIP code geographic area uses population density figures supplied by

the US Census Bureau to determine an area.

(2) The area is defined by the form of a polygon, not a circle.

(3) The "centroid" is found mathematically using waypoints marked along the

lines of the polygon AFTER the polygon is drawn...it is incidental to the

boundary of the arrea.

(4) The Gov't has spent BIG MONEY to ensure the accuracy of the LAT/LONS

of both the waypoints along the ZIP boundary and the centroid.

NOAA shifts or adjusts the numbers to further refine the accuracy.

 

So, the Postal service is unconcerned with where the center point of a ZIP is going to land. It could be in a wheat field, forest, your roof top or anywhere, and is

just a mark on a map.

 

For the geocacher using a ZIP Code to initiate a search, however, the waypoints listed will show up with distances measured away from that centroid, as though it were the center point of a circle.

 

Hope that this helps!

 

Mr Smiles

[+briansnat]

If I learned what I think I learned, then what I learned might help you.

 

(1) A ZIP code geographic area uses population density figures supplied by

the US Census Bureau to determine an area.

(2) The area is defined by the form of a polygon, not a circle.

(3) The "centroid" is found mathematically using waypoints marked along the

lines of the polygon AFTER the polygon is drawn...it is incidental to the

boundary of the arrea.

(4) The Gov't has spent BIG MONEY to ensure the accuracy of the LAT/LONS

of both the waypoints along the ZIP boundary and the centroid.

NOAA shifts or adjusts the numbers to further refine the accuracy.

 

So, the Postal service is unconcerned with where the center point of a ZIP is going to land. It could be in a wheat field, forest, your roof top or anywhere, and is

just a mark on a map.

 

For the geocacher using a ZIP Code to initiate a search, however, the waypoints listed will show up with distances measured away from that centroid, as though it were the center point of a circle.

 

Hope that this helps!

 

Mr Smiles

I don't think population density comes into play, but I think you are right on the other accounts

[+Muirwoody]

You can go to here and click on Acme Mapper and enter your zip code to see where the exact center of a zip code is.

[BassoonPilot]

When I type in our zip code, I see at the top of the page a place called Bottle Creek. Bottle Creek is many miles from us, up in the hills and is just that, a creek. There are no houses, much less a Post Office.

I see what you're talking about: The name displayed next to the zipcode at the top of "by postal code" search results.

 

I tried it for some of the local zipcodes I am very familiar with, and noticed some interesting anomalies:

 

07055 is the zipcode for the entire city of Passaic, NJ. Geocaching.com calls it "Dundee."

 

07011 through 07015 are the zipcodes for Clifton, NJ. All are called simply "Clifton" by geocaching.com except for 07012, which is called "Allwood." (Allwood is a neighborhood in Clifton.)

 

07470 is the main post office in Wayne, NJ. Interestingly, most sources incorrectly reference that zipcode to "Mountain View," the section of Wayne Township where the main post office was formerly located. Geocaching.com calls it "Lionshead Lake." (The main post office is not located in the "Lionshead Lake" section of Wayne.)

 

07501 through 07505 are the zipcodes for Paterson, NJ. For 07503, (the "Lakeview" section of Paterson,) geocaching.com reports "Paterson," but for 07502, geocaching.com reports "Hillcrest."

 

07424 is the zipcode for both West Paterson, NJ and Little Falls, NJ. Geocaching.com calls it "Great Notch."

 

07506 is the zipcode for Hawthorne, NJ. Somewhat surprisingly, Geocaching.com calls it "Hawthorne."

 

(I should add that in the preceding list, none of the inaccuracies amount to more than a couple of miles.)

Edited September 1, 2004 by BassoonPilot

[+Team DEMP]

When I type in our zip code, I see at the top of the page a place called Bottle Creek. Bottle Creek is many miles from us, up in the hills and is just that, a creek. There are no houses, much less a Post Office.

I see what you're talking about: The name displayed next to the zipcode at the top of "by postal code" search results.

Using http://zip4.usps.com/zip4/citytown.htm as a reference, it appears that for any zip codes that have more then 1 association, GC.com was using the 2nd record.

 

There are multiple sources for this data and I had previously used data from Zip*Data. It seems to match the way the postal service shows it on their site.

 

There's a default for each zip code and that's what should be used, but from BP's post, it's obviously not the case. Maybe this should be posted in the geocaching.com web site forum so it gets looked at. I'll post there now if I don't find any thread on it there already.

[+Mr Smiles]

If I learned what I think I learned, then what I learned might help you.

 

    (1)  A ZIP code geographic area uses population density figures supplied by

            the US Census Bureau to determine an area.

    (2)  The area is defined by the form of a polygon, not a circle.

    (3)    The "centroid" is found mathematically using waypoints marked along the

              lines of the polygon AFTER the polygon is drawn...it is incidental to the

              boundary of the arrea.

    (4)    The Gov't has spent BIG MONEY to ensure the accuracy of the LAT/LONS

              of both the waypoints along the ZIP boundary and the centroid. 

            NOAA shifts or adjusts the numbers to further refine the accuracy.

 

So, the Postal service is unconcerned with where the center point of a ZIP is going to land. It could be in a wheat field, forest, your roof top or anywhere, and is

just a mark on a map.

 

For the geocacher using a ZIP Code to initiate a search, however, the waypoints listed will show up with distances measured away from that centroid, as though it were the center point of a circle.

 

Hope that this helps!

 

Mr Smiles

 

Another thing that I THINK that I learned is the the NAME of a ZIP area is associated with the NAME given to a Quad Map (by USGS) of the area. This is why you get names for ZIP Code areas that don't always match the city or town where the mail goes.

 

This checked out in my area. Yours??

 

To find out, enter your ZIP, then click on the "Map It" icon. When the map comes up, copy the LAT/LON shown in the URL and enter it in the "View Maps" form at TopoZone.com to find the same centroid on a quad map (the "Show Target" button has to be checked to see it displayed) and see if it matches the name given for your ZIP.

 

Have fun today!

 

Mr Smiles

Edited September 1, 2004 by Mr Smiles