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Update README.md

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Carla
2015-07-02 13:08:34 +02:00
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geocoder/postal-codes/README.md
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@@ -146,10 +146,25 @@ Import the file ignoring step 2.
* All countries points [GeoNames](www.geonames.org) - http://download.geonames.org/export/zip/allCountries.zip
# Geocoder coverage map
![Map](https://camo.githubusercontent.com/483eae203445096ffa8bf0fe3d92a99fd9367a01/68747470733a2f2f646c2e64726f70626f7875736572636f6e74656e742e636f6d2f752f323837393330382f53637265656e25323053686f74253230323031352d30362d3239253230617425323031342e30332e34342e706e67)
# Known issues:
* The name of the countries added in a column are not being sanitized https://github.com/CartoDB/cartodb/issues/3392
# Known deficiencies of the service
* For the USA polygon zipcode service, Zipcode Tabulation Areas (ZCTA) are being used which [don't correspond to actual zipcode regions](http://web.archive.org/web/20050209030255/http://www.manifold.net/cases/zip_codes/zip_codes.html).
* Regarding the point geocoder service, being offered from GeoNames data: we've detected that the accuracy for a big section of zipcodes is not as good as intended, as GeoNames interpolates zipcode-populated place information. As an example, in the case of Madrid, Spain, all the zipcodes belonging to the city are geocoded in the centroid of the city itself.
This issue can be spotted easily by comparing interesecting zipcode points:
`SELECT the_geom, the_geom_webmercator, COUNT(*), adm0_a3 FROM postal_code_points GROUP BY the_geom, the_geom_webmercator, adm0_a3 HAVING COUNT(*) > 1 order by count(*)`
In this case, we conclude that most affected countries are Portugal, Mexico, Spain, Netherlands, Czech Republic or Slovakia, meanwhile Brazil doesn't show intersecting values.
The visual result of intersecting zipcodes is demonstrated in the following figure:
![Duplicates](https://camo.githubusercontent.com/1dbd4874830b0654b2fc2e11cd2a650d498f6bc9/68747470733a2f2f646c2e64726f70626f7875736572636f6e74656e742e636f6d2f752f323837393330382f53637265656e25323053686f74253230323031352d30362d3239253230617425323031322e35362e30332e706e67)
# Historic:
* [02/07/2015]:
* Adds known deficiencies and coverage map
* [24/06/2015]:
* Updated readme.md: added information about tables, function, indexes and the known issues section.
* Review and [upload functions](https://github.com/CartoDB/data-services/pull/152)