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zip codes are not geographic areas, they are a collection of mail delivery points. Sometimes those points are not geographically contiguous or may overlap
by mixdup 1y ago
zip codes are not geographic areas, they are a collection of mail delivery points. Sometimes those points are not geographically contiguous or may overlap
- PLenz 1y agoSometimes they're entire non geographic entities like the IRS
- mulmen 1y agoOr moving areas like aircraft carriers.
- PLenz 1y agoThe military postal code system is seperate from the US post office's zip code system. Often (and easily!) conflated but actually operating in parallel. Made even more confusing because many U.S. based entities can be reached in both systems.
- mulmen 1y agoNeat! The military postal codes look like ZIP9s, is that a coincidence or is that just the interface with the USPS?
- paulsmith 1y agoThis is a fact of ZIP Codes that a lot of people stumble one. I've worked on GIS/mapping projects in the past where stakeholders wanted or assumed ZIP Codes to be polygons. Another complexity that surprises folks is you can't guarantee a one-to-many state-to-ZIP Code relationship. There are several (I forgot offhand how many, I used to have them memorized) that span across state boundaries.
- y-c-o-m-b 1y agoYep, this fact eluded me earlier in the year. I was supposed to map out all ZIP codes in the US and color their boundaries based on certain stats we had. We were surprised to find many areas in the US were empty because they didn't have ZIP codes. I did a quick search and found out ZIP codes are driven by mail routes, and that instantly made sense to me, but the product stakeholders were very surprised to learn it.
- paulsmith 1y agoOne thing I just recalled is that if you maintain a small exceptions lookup table (i.e. the ones that span state boundaries), you can use ZIP Codes as a way to uniquely look up a county name.
- mulmen 1y agoWhy would you do this?
- paulsmith 1y agoFor example, health care plans in the US are county-specific with regard to premiums, co-pays, etc. (based on demographics). Allowing someone to type in their ZIP Code to get started can be a better user experience than having them pick their county. https://www.healthcare.gov/see-plans/ https://www.healthcare.gov/see-plans/
- chromatin 1y agoMy ZIP code happens to be shared by two separate cities and there are a few websites (Github, I'm looking at you) that will fail the payment, registration, etc. attempt if you don't enter the municipality that it THINKS is correct.
- dfxm12 1y agoWould ZIP+4 help here?
- stackskipton 1y agoYep, Zip + 4 is pretty pinpoint, generally it's no more than 20 residences and there is plenty of Zip + 4 that is single address.
- dhosek 1y agoA lot of P. O. Boxes have their own zip+4 address. You can spot these because the P.O. Box number and the +4 are usually the same (or occasionally the P.O. Box number is the last two digits of the five-digit zip code combined with the +4 so that a piece of mail with a box number and no zip code can be delivered to the correct post office in a large city).
- stackskipton 1y agoYea, PO Boxes generally have their own Zip Code so they use +4 for that. However, if you look at zip+4 for dwellings, it’s still few. My cul de sac with 5 houses has zip + 4 different from house on connecting street.
- dhosek 1y agoIt’s based at least in part on delivery routes. There’s a less-known 11-digit zip code which is unique for every delivery point (so down to the individual residence). I’m not sure if multiple apartments in the same building have distinct 11-digit zip codes, but this does imply that a zip+4 cannot have more than 100 delivery points within its bounds.
- voxadam 1y agoRelated: Stop Using Zip Codes for Geospatial Analysis (2019) - 184 points, 131 comments - https://news.ycombinator.com/item?id=42974728 https://news.ycombinator.com/item?id=42974728
- drecoe 1y agoZCTA[0] can (roughly) be used for this purpose https://www.census.gov/programs-surveys/geography/guidance/geo-areas/zctas.html https://www.census.gov/programs-surveys/geography/guidance/g...
- robseed 1y agoAnd census tools like Geocorr can translate between zip/zcta and other geographies, weighted by population or land area, without doing any spatial calculations. https://mcdc.missouri.edu/applications/geocorr2022.html https://mcdc.missouri.edu/applications/geocorr2022.html
- Bender 1y agozip codes are not geographic areas, they are a collection of mail delivery points. Indeed. My zip is from a neighboring state but has a -xxxx to route specifically to my mail distribution center. Even without the last 4 digits they manage to figure it out, just slower.