Experience I'm a Portland native but have lived in enough other places to gain a bit of perspective. I enjoy travel and learning about other places, so I want to help others learn more about Portland and get the most out of their trips here.
Expert: Diane Rynerson Date: 11/14/2003 Subject: Five Versus Four and Three and Five + Four
Question Hello,
I am from Manila and haven't been outside of my country ever. I am a consultant for ecommerce and web development and have a question of a general nature the typically informed American would most probably know about. I thought of posting my question here in the hope that you might be able to help me or at least point me to someone or some site that can.
I recently (inherited?) a database of zip codes of the United States. This database contains latitude and longitude coordinates and the zip codes themselves and its primary purpose is to assist in figuring out distances between zip codes. I've been able to find suitable material for computing distances from latitudes and longitudes, but it's the basic fundamental understanding of the zip codes themselves that has me lost.
The field representing zip codes contains three, four and five digit numbers. I am familiar with the five digit items but am confused about the three and four digit ones. I have tried searching for explanations about the three and four digit zip codes but the readily available resources I find provide unhelpful information on the matter. There is also mention of 5 + 4 digit zip codes and it confuses me even further. Most of the material published on the net speak about these zip codes such that they assume the reader understands what they are talking about already. Being a foreigner, I probably need it to be explained to me as if I were an eight year old.
Can you please explain to me why there are three, four and 5+4 digit zip codes aside from the five digit ones? I am aware that this question might not be of the kind you would expect on this site. I didn't know which category to place my question in but I figured that this matter about zip codes is common knowledge to all Americans. I also assumed that since you are an authority on various matter in this category, the chances are good that I can find the answers I seek and probably ask you to indulge my being uninformed.
I'd also like to offer my services as an ecommerce/web/technical resource in exchange, as an expression of goodwill. I hope to be of help in a simple question or two or even some simple scripting/programming work that you might have lying around in return. I appreciate the time you've taken to at least read this post, and I believe a good turn deserves another. It may be that you might not need any assistance at this point in time for such services or advice in this area, but I hope you do keep me in mind if and when the opportunity arises. I claim to be no guru in this department, but hopefully at the right time with the right person under the right circumstances, I might be of use.
Thanks in advance and I hope that your role as expert at this website expands and prospers.
Sincerely,
Johnny
publicinbox@hotmail.com
Answer The US Post Office has FAQs about zip codes at http://www.usps.com/zip4/zipfaq.htm. If you read all of them, you will know way more about zip codes than most Americans.
I, too, am confused about the three and four-digit codes you've found in your database, and I wonder if they could have been entered in error.
In the olden days, before zip codes, we had two digit "zones." The zones represented a place in a city. For example, my zone address was Portland, 12, Oregon. The post office sorted mail first by state, then by city, then by zone, then by street address. With the coming of zip codes, three digits were added in front of the zones. That portion of my address became Portland, OR 97212. 97 represented the state of Oregon. 972 specifically meant Portland, 12 represented my part of Northeast Portland. Postal employees no longer needed to read "Portland, OR" when they had the five-digit zip codes. Increasingly, the post office moved to mechanized reading and sorting. Often you'll see on mail from the United States a bar code which contains zip code information to aid in this mechanized process.
Much more recently, the "zip plus four" concept was introduced. The basic five-digit zip code remains, but a very specific four-digit number is added, again to help with mechanized reading for sorting. Sometimes the four digits stand for a city block, a specific building, or even, in a high rise apartment or office, a few floors. The average American doesn't use the "plus four" zip code. I don't even remember mine. It is required, though, for bulk mailings, so it is probaby very important in your database.
This brings us back to your basic problem of the inherited database. My guess is that it is, unfortunately, quite unreliable.
Please let me know if you have other questions, follow-up or otherwise.
