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
Related
I am developing iOS 5 app which I want to communicate with server providing information about the nearby places for a given location: places locations and annotations. I want to use MapKit to populate my map with this information.
I didn't find any straightforward information regarding the following questions:
Does MapKit has tiles functionality (Google Maps way) out-of-the-box and do I need to work on it additionally, if not?
What is the best practice of retrieving places information (markers positions and annotations) from server?
Is it possible to cache this information so an user can see the nearby places of "his city" in offline mode?
Actually questions 2 and 3 are interrelated: they both address the problem of not retrieving an information (locations + annotations) that is already on map multiple times.
Hopefully I am not overlooking something obvious here.
Thanks!
Update 1: (Regarding places, not maps) More specifically I am interested in, how should I create a "hand-crafted" logical tiles for regions containing the places I fetch from the server, so they would not require refetching themselves when user scrolls the map? I know I can dive into implementing this functionality myself. For example, should I write the places just fetched to a local storage using Core Data immediately after fetching them or organize some queue? Or how could I know when I need to perform a request about the specific region on server and when I just fetch local data that is already on the device? I just want to know, are there any recommended approaches, best practices? Hopefully, I wrote it clear here.
Update 2: I am wondering about best practices here (links, example) not to start creating all this (points 2+3) from scratch. Are there any frameworks incapsulating this or good tutorials?
#Stanislaw - We have implemented the functionality you describe in an app called PreventConnect for one of our clients. The client already had some data stored out in a Google Fusion table. We extended their existing solution by adding another Google Fusion table which stores the geocoordinates for a number of locations. All this being said, to answer your questions...
1) The map portion itself is pretty out of the box, the tiles and what not, but you'll need to do some coding to get zoom extents, pin drops, annotations, and things like that working the way you expect them to work.
2) We found the Google Fusion solution to be quite effective. If you don't want to use Google Fusion there are other cloud database providers like StackMob, database.com, and many others. Google is free and they have an iOS SDK that makes communicating with Google Fusion pretty simple.
3) Absolutely! We cache much of the data in a Core Data store locally on the device. This greatly improves performance and responsiveness.
Time to write a solid answer to this my question (I could have it written a year ago but somehow I lost it from my mind).
Does MapKit has tiles functionality (Google Maps way) out-of-the-box and do I need to work on it additionally, if not?
The answer is yes: MapKit does have it. The keywords here are overlays (MKOverlay, MKOverlayView and others). See my another answer.
See also:
WWDC 2010 Session: Customizing Maps with Overlays,
Apple-WWDC10-TileMap.
What is the best practice of retrieving places information (markers positions and annotations) from server?
Actually since then I didn't learn a lot about "best practices" - unfortunately, nobody told me about them :( - that is why I will describe "my practices".
First of all, there are two strategies of populating a MapKit map with places:
The first strategy is about populating your map with the places by demand: imagine you want to display and see all places nearby (for example, no more than 1km from current user location) - this approach assumes that you ask your server only the places for the box you are being interested in. It means something like: "if I am in Berlin (and I expect 200 places for Berlin), why should I ever fetch the places from Russia, Japan, ... (10000+ places)".
This approach leads to relying on "tiles" functionality that question N1 address: Google maps and Apple maps are usually drawn using 'tiles' so for your "Berlin" portion of map you rely on corresponding "Berlin" tiles that are drawn by MKMapView - you use their dimensions, to ask your server only the places within the "Berlin" box (see my linked answer and the demo app there).
Initially this was the approach I've used and my implementation worked perfectly but later I was pushed to use second approach (see below) because the problem of clustering appeared.
The second strategy is to fetch all the places at once (yeah, all this 10000+ or more) and use Core Data to fetch the places needed for the visible portions of map your are interested in.
Second approach means, that during the first run you send your server a request to fetch all places (I have about 2000 in my app). Important here is that you restrict the fields you fetch to only geo-ones that you really need for your map: id, latitude, longitude.
This 'fetch-all' fetch has a significant impact on my app's first start time (On "the oldest" iPhone 4, I have near 700ms for the whole Fetch + Parse-JSON-into-Core-Data process, and extensive benchmarks show me that it is Core Data and its inserts is a bottleneck) but then you have all the essential geo-info about your places on your device.
Note, that whatever strategy you use, you should do a process of fetching these geo-points efficiently:
Imagine Core Data entity Place which has the following fields structure (preudo-Objective-C code):
// Unique identificator
NSNumber *id,
// Geo info
NSNumber *latitude,
NSNumber *longitude,
// The rest "heavy" info
NSString *name,
NSString *shortDescription,
NSString *detailedDescription, etc
Fetching places efficiently means that you ask only your place records geo-data from your server to make the process of this mirroring as fast as possible.
See also this hot topic: Improve process of mirroring server database to a client database via JSON?.
The clustering problem is out of scope of this question but is still very relevant and affects the whole algorithm you use for the whole proces - the only note I will leave here is that all the current existing clustering solutions will require you to use second strategy - you must have all the places prepared before you run into the clustering algorithms that will organize your places on a map - it means that if you decide to use clustering you must use strategy #2.
Relevant links on clustering:
WWDC 2011 Session: Visualizing Information Geographically with MapKit,
How To Efficiently Display Large Amounts of Data on iOS Maps,
kingpin - Open-source clustering solution: performant and easy-to-use.
Is it possible to cache this information so an user can see the nearby places of "his city" in offline mode?
Yes, both strategies do this: the first one caches the places you see on your map - if you observed Berlin's portion of map you will have Berlin part cached...
When using the second strategy: you will have all essential geo-information about your places cached and ready to be drawn on a map in offline mode (assuming that MapKit cached the map images of regions you browse in offline mode).
I'm working on an iOS app that pulls events from Google Calendar and subsequently generates pins on a map for each event (based on what the event creator fills in for "Location"). The user can select a date range (today, this week, this month, etc.) and see all the events taking place near them over that period.
Problem 1: The app is for my local university, so a majority of the locations will be buildings on campus. These buildings have inconsistent addresses that are often difficult to find, so it would be good if the location "Foo Hall" would result in a pin on that building. Google Maps is capable of doing this, however Apple Maps has no knowledge of the buildings on my school campus.
Problem 2: In an ideal situation, thousands of students would be using this app. Each time they open the app, they could be viewing dozens of pins. Therefore, I'm worried that I may be pushing the limits imposed by Google's geocoding API (definitely the 2500 request limit, and maybe even the 100,000 request limit for the Business API).
So my question is... what would be the best solution for these two problems? Should I create a local database for building names and map them to coordinates? Or is there a way I can overcome the limitations of Google's Geocoding API? Is there a better solution I'm not thinking of?
Thanks for any help!
I would use latitude and longitude coordinates for the buildings and allow for people to add locations to the database if they are meeting somewhere that you have not added already. This way, the pins will drop in the center of the building if you want them to, because you are not relying on an address or on looking up a building name. You simply know that "Foo Hall" is at X latt. and Y long. And if someone selects "Foo Hall" or sees an event at "Foo Hall" there is a perfectly placed pin right in the middle of it on the map. I don't think you need to worry as much about the geocoding API if you are using hardcoded locations for the buildings either, because you won't have to be polling Google to get the building locations.
I would also use some sort of server to store the building locations so they can be updated or added to, either by you or by the users.
That's how I would handle it, good luck!
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
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
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.