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I have a large dataset of polygons for property sections that I need to reverse geocode. It was recommended that I use a GIS like Quantam to do this however from my research I am not 100% sure if a GIS will support doing this.

The technique that I was going to use until I found GIS was to get the center co-ordinates of the polygon and then pass these co-ordinates into a reverse geo-coding api like google or openstreetmap. However I am not sure if this is very accurate.

The polygon data is in the projection format WGS 84 (EPSG:4326 Lat/Long)

Here is an example of what one of the polygons data looks like:

MULTIPOLYGON (((174.76394635 -41.34094115,174.763921416699986 -41.340960566699998,174.763611683300013 -41.340978616699999,174.763597816700013 -41.3409202,174.763793716700008 -41.340691133299998,174.7638963 -41.34071535,174.763958516700001 -41.34073005,174.76394635 -41.34094115)))

What is the best way to reverse geocode this polygon data?

How can I do it on a large scale?

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What is you area of interest? ie- Where do you want to be able to determine reverse geocode values for? country? continent? global? –  RyanDalton Aug 26 '13 at 14:54
    
@startupsmith, did you find any solution to this? –  PostureOfLearning Aug 29 '13 at 0:41

1 Answer 1

Your results will only be as accurate as the weakest link in your data and methods. Reverse geocoding large polygons is inherently inaccurate if you have no intelligent method to determine a point location from the area. If so, a centroid could be the best bet. Reverse geocoding this will (afaik) snap to the nearest street and have the address interpolated from the range this street represents.

One possible option to accomplish this on a large scale is to script it using python. You can use Shapely to access the spatial information in python, then pygeocoder to reverse geocode the centroid of the polygons.

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Thanks for your reply. My findings from using the centroid are that when using it with openstreetmap it does only give the street but with google maps I get the exact address. From my understanding I won't be able to do this on a large scale with google maps. Any ideas why it works with google and not openstreetmap? –  startupsmith Jun 27 '13 at 3:17
    
Housenumbers are not included in Openstreetmap everywhere around the world. If noone has gathered that information, you can not expect the geocoder to return that information. –  Andre Joost Jun 27 '13 at 4:08
    
@Andre Ok thanks. Any ideas if there is a way to do this on a large scale then? Or would it be possible to do with google maps and somehow stay within their rate limits? –  startupsmith Jun 30 '13 at 3:22

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