[Open-data-census] Dataset Definitons

Thu Oct 3 19:42:24 BST 2013

Hi everyone,

I was asking myself the same question. For example, in Tunisia, zipcodes are published by the official website of Tunisian postal company (a public company) via a search engine
http://www.poste.tn/codes.php

It gives the locality name to which the zip code relates, but not the latitude and longitude.

For the moment I put "unsure" for this dataset in Tunisia, because I agree with you Andrew, it would be only relevant in terms of OpenData if we have latitude and longitude.

So should I consider that the data exist ? And should I consider that the data is publicly available, since there's not any table presenting all zip codes and we have to make search requests to get each zip code ?

Regards,

Amin

________________________________
 De : Andrew Stott <andrew.stott at dirdigeng.com>
À : 'Rufus Pollock' <rufus.pollock at okfn.org>; 'open-data-census' <open-data-census at lists.okfn.org> 
Envoyé le : Jeudi 3 octobre 2013 20h12
Objet : Re: [Open-data-census] Dataset Definitons

Rufus

Thanks for your post http://lists.okfn.org/pipermail/open-data-census/2013-October/000219.html

However I’d like to push back *strongly* on the proposed change to the definition of “postcodes/zipcodes and their corresponding geolocations” and, in particular, defining geolocations as “boundaries/areas corresponding to those postcodes”

“boundaries” can be very demanding – it requires the trace of the boundaries, which may or not be recognised administrative boundaries.  In some cases the boundaries overlap because of how postcodes are defined (they generally reflect collections of delivery points linked to delivery offices and not recognised administrative boundaries – see for instance the complexities in the US http://en.wikipedia.org/wiki/ZIP_code  It also may involve more than one government agency to put the data together.

What is meant by “areas” – is this a geospatial bounding area (ie a rectangle) or the *name* of the town to which the postal code relates - which makes sense in Australia and, to some extent, the US, but which means a data loss in countries such as the UK, Canada and the Netherlands which have finer grained postal codes.  And turning a postal code into the name of a town is not necessarily very useful.  A number of postcode databases already identified in the Census give the name of the street in which the postcode is.

In my experience the two standard use case of a postcode database and geolocations which I have seen is as follows:

(1) I have a table of data in which each row has an attribute which is or contains a postcode (perhaps as part of a postal address) – for instance points of interest, crimes, houses for sale.  I want to plot each row on a map.  So I need to translate the postcode into a lat/long.  A database of postcodes and their lat/long (or the eastings and northings in the national coordinate system, which can be converted to lat/longs by well known formulae) allows me to do that.

(2) I have an application in which I want the user gives a location by postcode as a shorthand for the address, and I want to use that location to describe the issue or to find other relevant locations.  The classic examples are http://www.fixmystreet.com/  or a “where is my nearest?” application (cf http://maps.camden.gov.uk/ ) including the famous toilet finders.  Again I need to be able to convert the postcode into a lat/long or equivalent, and then use it to locate the problem or measure distances to other similarly coded locations.

In both these use cases the key requirement is that the database should be of postcodes and their corresponding geospatial co-ordinates (in lat/long or a system convertible to lat/long).  Your proposed definition does not ensure that.

So I would instead make obtaining a lat/long as the key requirement.  I would also allow cases where the corresponding location information (eg town name) could be converted to lat/long through the use of other open data (eg an open address register or gazetteer with lat/longs) 

So I propose an alternative definition:

“a database of postcodes/zipcodes and a corresponding geospatial locations in terms of a latitude and a longitude (or similar co-ordinates in an openly published national co-ordinate system).  A database which gives a location in terms of the name of a town or a street without lat/long co-ordinates is not acceptable unless the name of the town or street can be further converted to a latitude and longitude by means of other open data (eg an open gazetteer with latitude and longitude attributes).”

Regards

Andrew

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