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Geocode: Lack of precision in large cities?  XML
Forum Index -> Postal Codes
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speedy



Joined: 17/11/2006 21:10:37
Messages: 1
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I'm a little confused of how the precision of longitude/latitude diminishes in larger cities. I'm using the PostalCodeSearch service.

Example, these two zip codes for santa barbara 93101 and 93130 returns different longitude/latitude points; while these two (90007 and 90210) for Los Angeles returns the same one.
This is true for Copenhagen, Denmark as well, where the countryside is highly precise - while zip codes in Copenhagen like 1114 and 2200 returns the same lon/lat point..

Is this me using this service in the wrong way or is the data for metropolitan areas not of a higher quality?

Alternatively you can send me the postal code db, and I'll take a look.

Thanks in advance and thanks for providing this service.
marc



Joined: 08/12/2005 07:39:47
Messages: 3990
Offline

Hi speedy

Your observations are correct. In large cities we don't have a corresponding place name in the main geonames database. We therefore have to use the same lat/lng for several postal codes. For the US the lat/lng are derived from a dataset provided by the US census. I don't know why 90007 and 90210 have the same lat/lng in this dataset.

Regards

Marc

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