![]() Download free ESRI shapefile maps. Download free shapefile maps. The source code for reading the shapefiles is included in the directory SHPreader. Sources for US Zip Code Boundaries? A five- digit ZIP code covers an arbitrary collection of delivery points (addresses). The USPS is the sole determiner of what ZIP code is assigned to what address, so they are the best source of current and correct data, which changes monthly. Cheap sources of current data are vendors like Semaphore Corporation. Addresses within a ZIP code are assigned to numbered delivery routes. ![]()
Zip Code Shapefiles By StateAddresses along the route are visited in a specific order, however there is no guarantee what path is taken by the mail carrier between two points along the route, so attempts at plotting routes as lines (or plotting all routes in a ZIP as a collection of lines) can't always be accurate. Because ZIP codes are collections of points, the concept of "boundary" is ambiguous. It might mean computing the minimum rectangular bounding box enclosing all the addresses in a ZIP, or using a Graham scan to compute a "tighter" polygon, or using Lloyd's algorithm to polygonize a map, but how to choose the "best" boundary isn't always clear as shown in these 3 different boundaries for 5 points. Since all addresses for a ZIP will be served by a single post office, it's tempting to start with that office's city boundary as the encompassing border for all ZIP codes served by that office, but exceptions occur: for example, a post office will serve ZIP codes outside the city, such as in unincorporated towns. Small towns often don't have street delivery; everything for a ZIP code might go to post office boxes at one location. And just over 1. 00 "unique" ZIP codes are reserved for schools and businesses at a single location. Such as ESRI ArcGIS (shapefile). ZIP Code boundaries in Chicago. To download, right-click the "Download" link above and choose "Save link as.".
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