Finding City and Zip Code for a Location - mapping

Given a latitude and longitude, what is the easiest way to find the name of the city and the US zip code of that location.
(This is similar to https://stackoverflow.com/questions/23572/latitude-longitude-database, except I want to convert in the opposite direction.)
Related question: Get street address at lat/long pair

Any of the online services mentioned and their competitors offer "reverse geocoding" which does what you ask--convert lon/lat coordinates into a street address of some-sort.
If you only need the zip codes and/or cities, then I would obtain the Zip Code database and urban area database from the US Census Bureau which is FREE (paid for by your tax dollars). http://www.census.gov/geo/www/cob/zt_metadata.html.
From there, you can either come up with your own search algorithm for the spatial data or make use of one of a spatial databases such as Microsoft SQL Server, PostGIS, Oracle Spatial, ArcSDE, etc.
Update: The 2010 Census data can be found at:
http://www2.census.gov/census_2010/

This is the web service to call.
http://developer.yahoo.com/search/local/V2/localSearch.html
This site has ok web services, but not exactly what you're asking for here.
http://www.usps.com/webtools/

You have two main options:
Use a Reverse Geocoding Service
Google's can only be used in conjunction with an embedded Google Map on the same page, so I don't recommend it unless that is what you are doing.
Yahoo has a good one, see http://developer.yahoo.com/search/local/V3/localSearch.html
I've not used OpenStreetMap's. Their maps look very detailed and thorough, and are always getting better, but I'd be worried about latency and reliability, and whether their address data is complete (address data is not directly visible on a map, and OpenStreetMap is primarily an interactive map).
Use a Map of the ZIP Codes
The US Census publishes a map of US ZIP codes here. They build this from their smallest statistical unit, a Census Block, which corresponds to a city block in most cases. For each block, they find what ZIP code is most common on that block (most blocks have only one ZIP code, but blocks near the border between ZIP codes might have more than one). They then aggregate all the blocks with a given ZIP code into a single area called a Zip Code Tabulation Area. They publish a map of those areas in ESRI shapefile format.
I know about this because I wrote a Java Library and web service that (among other things) uses this map to return the ZIP code for a given latitude and longitude. It is a commercial product, so it won't be for everyone, but it is fast, easy to use, and solves this specific problem without an API. You can read about this product here:
http://askgeo.com/database/UsZcta2010
And about all of your geographic offerings here:
http://askgeo.com
Unlike reverse geocoding solutions, which are only available as Web APIs because running your own service would be extremely difficult, you can run this library on your own server and not depend on an external resource.

If you call volume to the service gets up too high, you should definitely consider getting your own set of postal data. In most cases, that will provide all of the information that you need, and there are plenty of db tools for indexing location data (i.e. PostGIS for PostgreSQL).

You can buy a fairly inexpensive subscription to zipcodes with lat and long info here: http://www.zipcodedownload.com/

Or google's reverse geocoding
link
http://maps.google.com/maps/geo?output=xml&q={0},{1}&key={2}&sensor=true&oe=utf8
where 0 is latitude 1 is longitude

geonames has an extensive set of ws that can handle this (among others):
http://www.geonames.org/export/web-services.html#findNearbyPostalCodes
http://www.geonames.org/export/web-services.html#findNearbyPlaceName

Another reverse geocoding provider that hasn't been listed here yet is OpenStreetMap: you can use their Nominatim search service.
OSM has the (potentially?) added bonus of being entirely user editable (wiki-like) and thus having a very liberal licencing scheme of all this data. Think of this of open source map data.

Related

Offline reverse geocoding on iOS

There are lots of existing questions relating to this issue, but I have looked at as many of them as I could find and did not get an answer.
I'm trying to perform an offline reverse geocoding lookup on iOS based on a latitude and longitude. I'd like to be able to provide a latitude and longitude, and be provided with the country in which that point lies. I can do this with Geonames (such as: http://api.geonames.org/countryCode?lat=45.03&lng=8.2&username=demo), but I need a similar ability offline, without Internet functionality on the device.
CLLocation does not provide offline services that work reliably enough for what I'm doing, it relies on caches made while you were previously online, etc. Messy.
I've tried this: https://github.com/drodriguez/reversegeocoding but haven't had any luck, it requires some slightly complex / confusing Terminal installations using something called Thor which I've never heard of, and was throwing up a variety of errors, so I bailed on it.
I've found a few downloadable maps, but these seem to be even more complicated, and worryingly, hundreds of megabytes or even gigabytes in size – much beyond the scope of an iOS app. I only need countries, nothing smaller than that (cities, streets, locations, etc.) so I think I should be able to get a much smaller file.
So my key question is: is there some pre-existing database or tool, preferably with iOS support, that I can feed a latitude/longitude, and get a country? And, if not, what steps should I take to get such functionality working on my own?
Thanks in advance.
ReverseGeocodeCountry is a simple lightweight offline country reverse geocoder for iOS, it has a static JSON file with country polygon data that is used to reverse geocode any lat/lng:
https://github.com/krisrak/ios-offline-reverse-geocode-country
The "Countries of the World" is a .csv text file with countries, coordinates, localised country names, capitals and other information. It seems to be free to use. You just have to import it into an SQLite database.
Edit Just noticed you want reverse geocoding. The database would only be good for forward geocoding.
You can download shapefiles for all countries at http://www.gadm.org/download. If you download a .kmz, you can unpack it to a list of coordinates for the borders. You could probably take every 5th or 10th coordinate to get smaller size (with less accuracy).
Just in case I can suggest another good written offline geocoding library.
https://github.com/Alterplay/APOfflineReverseGeocoding

How do I write a "find nearest" algorithm? e.g. a store / branch locator by address / zip / "my location"

My need is simple and commonly implemented in any location based app today, display to a user a list of all "things" in his/her area (or by a zip code / address)
Using Google Maps API (especially the new "store locator library") sounds like the safest bet, but if I would like to develop something on my own, is there a "standard" way to do so? what are the options? Yahoo geo-location API (and reverse lookup)? (Google Maps API require to use their map, not just API) purchace ZIP code files? other 3rd party services? online? offline? what is the secret?
Hmm. Zip codes can be handled a number of ways, and it helps to get a general background on how they work: http://en.wikipedia.org/wiki/ZIP_code
I'd purchase a USPS database with GPS coordinates, and work from there. A simple SELECT SQL query, with a LIMIT or TOP 10 (or however many search results you'd like) when calculating the magnitude of the vector should work here.
It's been a while, but the algorithm for vector calculation is fairly simple, and should be easy to implemented in SQL: http://www.netcomuk.co.uk/~jenolive/vect5.html

Geolocation, Is it possible to get latitude and longitude from address and store locally in my database

I want to be able to run queries locally comparing latitude and longitude of locations so I can run queries for certain addresses I've captured based on distance.
I found a free database that has this information for zip codes but I want this information for more specific addresses. I've looked at google's geolocation service and it appears it's against the TOS to store these values in my database or to use them for anything other than doing stuff with google maps. (If somebody's looked deeper into this and I'm incorrect let me know)
Am I likely to find any (free or pay) service that will let me store these lat/lon values locally? The number of addresses I need is currently pretty small but if my site becomes popular it could expand quite a bit over time to a large number. I just need to get the coordinates of each address entered once though.
This question hasn't received enough attention...
You're correct -- it can't be done with Google's service and still conform to the TOS. Cheers to you for honestly seeking to comply with the TOS.
I work at a company called SmartyStreets where we process addresses and verify addresses -- and geocode them, too. Google's terms don't allow you to store the data returned from the API, and there's pretty strict usage limits before they throttle or cut off your access.
Screen scraping presents many challenges and problems which are both technical and ethical, and I don't suppose I'll get into them here. The Microsoft library linked to by Giorgio is for .NET only.
If you're still serious about doing this, we have a service called LiveAddress which is accessible from any platform or language. It's a RESTful API which can be called using GET or POST for example, and the output is JSON which is easy to parse in pretty much every common language/platform.
Our terms allow you to store the data you collect as long as you don't re-manufacture our product or build your own database in an attempt to duplicate ours (or something of the like). For what you've described, though, it shouldn't be a problem.
Let me know if you have further questions about address geocoding; I'll be happy to help.
By the way, there's some sample code at our GitHub repo: https://github.com/smartystreets/LiveAddressSamples
http://www.zip-info.com/cgi-local/zipsrch.exe?ll=ll&zip=13206&Go=Go could use a screen scraper if you just need to get them once.
Also Microsoft provides this service. Check if this can help you http://msdn.microsoft.com/en-us/library/cc966913.aspx

Techniques for offline reverse geocoding on a mobile device?

I am working on a mobile mapping application (currently iOS, eventually Android) - and I am struggling with how to best support reverse geocoding from lat/long to Country/State without using an online service.
Apple's reverse geocoding API depends on Google as the backend, and works great while connected. I could achieve similar functionality using the Open Street Maps project too, or any number of other web services.
What I really want however is to create a C library that I can call even when offline from within my application, passing in the GPS coordinates, and having it return the country and/or state at those coordinates. I do not need finer granularity than state-level, so the dataset is not huge.
I've seen examples of how to do this on a server, but never anything appropriate for a mobile device.
I've heard Spatialite might be a solution, but I am not sure how to get it working on iOS, and I wonder if it may be overkill for the problem.
What are some recommended techniques to accomplish this?
Radven
You will need to get the Shapefiles (lat/lng outline) of all the administrative entities (US states, countries, etc). There are a lot of public domain sources for these. For example, the NOAA has shapefiles for US states and territories you can download:
http://www.nws.noaa.gov/geodata/catalog/national/html/us_state.htm
Once you got the shapefiles, you can use a shapefile reader to test if a lat/lng is within a shape. There are open source readers in C, just google. I seen stuff at sourceforge for shapefiles, but have not used these myself.
The Team at OpenGeoCode.Org
If you're looking for an approach based on a quadtree, try Yggdrasil. It generates a quadtree based on country polygon data. A Ruby example script can be found here.
I can suggest good written offline geocoding 3rd party library.
https://github.com/Alterplay/APOfflineReverseGeocoding

Physical Address to GeoLocation UK

Is there a good physical address to GeoLocation conversion database in the UK? I am trying to use this to build a globrix style search box http://www.globrix.com/ for a web application. Any pointers will be nice. I have been searching for hours. I have found several that convert UK Postcodes into Geolocation. But I need the addresses listed as on Globrix.
The Google Maps API provides a geocoder webservice that you can actually use independently of Google Maps itself. You send it the address/postcode, and it responds with a lat/long plus disambiguated addresses. We use it server-side in the UK to do address lookup. It's incredibly quick, too.
http://code.google.com/apis/maps/documentation/geocoding/index.html
http://www.postcodeanywhere.co.uk should be able to help with this. Alternatively, you can buy the "PAF" (Postcode Address File) from the Royal Mail, but it is expensive.
Update for information relating UK geolocations in 2020. Since 2009:
Google's Geocoder has gotten an order of magnitude more expensive in 2018. It's ~0.5c per search with no free tier
Office for National Statistics have released a free postcode directory called ONSPD. This means if you have the postcode of your address, you can resolve a geolocation accurate to the postcode centroid (this may be 10-100m or so out). There's a free public service API available at https://postcodes.io which allows you to forward or reverse geocode a postcode. There are also public docker data and application images which allow you to host this easily
If you're interested in Rooftop accurate geocodes, a change in Ordnance Survey licensing in 2020 has meant its much simpler and cheaper to access geolocations for almost every premise in Great Britain from Ordnance Survey by combining it with Royal Mail PAF (Postcode Address File). As of September 2020, I think https://ideal-postcodes.co.uk is currently the only company to offer complete and authoritative rooftop geolocations under these new rules. It's likely other PAF vendors will catch up over the coming years.
Disclaimer: I'm the author of postcodes.io and work for ideal-postcodes.co.uk

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