iOS5 Reverse Geocoding Limitations

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I'm using the Reverse Geocoding provided by Apple (Linked to the dev documentation at the bottom of this post).

I have set this up to work with my current project. When I touch the map, the touchPoint is converted to coordinates which I use with my reverse geocoding. The problem is though, that I only get information regarding address (street, housenumber, country and so on) when I geocode a location from Europe, North America and parts of South America. I do NOT get this information when doing a reverse geocoding on coordinates from Africa and Asia.

I used Forward Geocoding (some random addresses in Africa and Asia) to check if these could be found with all the information. And they could - the forward geocoding works brilliant.

So how can it be, that I don't get address information when I reverse the geocoding with coordinates from especially Africa and Asia? Anyone experienced the same thing?

http://developer.apple.com/library/ios/#documentation/UserExperience/Conceptual/LocationAwarenessPG/UsingGeocoders/UsingGeocoders.html#//apple_ref/doc/uid/TP40009497-CH4-SW1)

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I can't find any good references, but I suspect that Apple only has the reverse geocoding info for Europe and North America. Apple is moving away from Google and towards TomTom, which doesn't have a very strong presence in Africa and Asia. I wonder if reverse geocoding works for points in australia? - Adam Davis
That may very well be it. Reverse geocoding does not work for points in Australia. Only city names will appear (Street, house, postalcode and so on are missing). Thanks for the comment Adam. - asklausen
For Russia, Reverse geocoding also works(and it was very unreliable before iOS5), except you don't get zip code(but get street/house) - dkzm

1 Answers

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Reverse GeoCoding (See error message returned kCLErrorGeocodeFoundPartialResult and kCLErrorGeocodeFoundNoResult). Many times only the US, Europe and densely populated cities of the world return full reverse address information.

When kCLErrorGeocodeFoundPartialResult occurs, that mean only a portion of the reverse geocode information is available. This may be the street name (individual addresses, meaning house/bdlg or lot#) is not available. This could be less and less information down to just the country name.

This is because for use with Google, the satellites only return lat & lon. It is up to Google or other mapping companies to provide data points and data point region information (meaning lat/lon and span around that point that a bldg would occupy for an address). Because this information has to be acquired from each and every single municipality around the world, then verified and data entered - it is a HUGE undertaking for which Google has been actively doing for over 10 years. In this time, there is less than 7% of the earth's land masses that is majority geocoded. Adding to this difficulty is that the US and the Majority of Europe are relatively well organized at the municipality level with up to date maps and parcel/lot locations. That same is not true for many other areas of the world.

So it is up to you, the developer, to sift through the available information and structure the annotation callout information that makes the most sense from the limited information returned. Again, this may just be the Country Name.

Also, don't forget about Ocean and InlandWater fields for if you user drops a pin in the great Lakes or the Hudson River.

the Name field is also helpful for Landmarks.

Yes, in the end, there is a lot of juggling to figure out how best to display place mark data returned from a reverse geocode lookup, but your users will thank you for trying out every possibility you can think of.

The above information as well as lists for full geocode and partial geocode countries is in the Apple Documentation. You would be surprised to see just how few countries there are on those lists!