Defining areas using postcodes John Langley 27 th April 2007 at The Riverside Centre Derby.
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Transcript of Defining areas using postcodes John Langley 27 th April 2007 at The Riverside Centre Derby.
![Page 1: Defining areas using postcodes John Langley 27 th April 2007 at The Riverside Centre Derby.](https://reader036.fdocuments.in/reader036/viewer/2022062500/5697bff31a28abf838cbc4d2/html5/thumbnails/1.jpg)
Defining areas using postcodes
John Langley
27th April 2007at The Riverside Centre Derby
![Page 2: Defining areas using postcodes John Langley 27 th April 2007 at The Riverside Centre Derby.](https://reader036.fdocuments.in/reader036/viewer/2022062500/5697bff31a28abf838cbc4d2/html5/thumbnails/2.jpg)
Define the area by…
• Moving from the area “on the ground” to a useful abstraction
• Using large scale OS maps
• Drawing a boundary line defining the area
• Fitting postcode centroids to the area
• Example: Manton Community Alliance (Neighbourhood Management Area)
![Page 3: Defining areas using postcodes John Langley 27 th April 2007 at The Riverside Centre Derby.](https://reader036.fdocuments.in/reader036/viewer/2022062500/5697bff31a28abf838cbc4d2/html5/thumbnails/3.jpg)
![Page 4: Defining areas using postcodes John Langley 27 th April 2007 at The Riverside Centre Derby.](https://reader036.fdocuments.in/reader036/viewer/2022062500/5697bff31a28abf838cbc4d2/html5/thumbnails/4.jpg)
![Page 5: Defining areas using postcodes John Langley 27 th April 2007 at The Riverside Centre Derby.](https://reader036.fdocuments.in/reader036/viewer/2022062500/5697bff31a28abf838cbc4d2/html5/thumbnails/5.jpg)
![Page 6: Defining areas using postcodes John Langley 27 th April 2007 at The Riverside Centre Derby.](https://reader036.fdocuments.in/reader036/viewer/2022062500/5697bff31a28abf838cbc4d2/html5/thumbnails/6.jpg)
Digitise the boundary (or just draw round it)
![Page 7: Defining areas using postcodes John Langley 27 th April 2007 at The Riverside Centre Derby.](https://reader036.fdocuments.in/reader036/viewer/2022062500/5697bff31a28abf838cbc4d2/html5/thumbnails/7.jpg)
Which spatial dataset?
Codepoint?
![Page 8: Defining areas using postcodes John Langley 27 th April 2007 at The Riverside Centre Derby.](https://reader036.fdocuments.in/reader036/viewer/2022062500/5697bff31a28abf838cbc4d2/html5/thumbnails/8.jpg)
Which spatial dataset? NHS Postcode Directory
![Page 9: Defining areas using postcodes John Langley 27 th April 2007 at The Riverside Centre Derby.](https://reader036.fdocuments.in/reader036/viewer/2022062500/5697bff31a28abf838cbc4d2/html5/thumbnails/9.jpg)
Codepoint vs NHS PC
![Page 10: Defining areas using postcodes John Langley 27 th April 2007 at The Riverside Centre Derby.](https://reader036.fdocuments.in/reader036/viewer/2022062500/5697bff31a28abf838cbc4d2/html5/thumbnails/10.jpg)
Which spatial dataset? NHS PC Dir has Current postcodes
![Page 11: Defining areas using postcodes John Langley 27 th April 2007 at The Riverside Centre Derby.](https://reader036.fdocuments.in/reader036/viewer/2022062500/5697bff31a28abf838cbc4d2/html5/thumbnails/11.jpg)
Which spatial dataset? NHS PC Dir is also historical (coloured symbols)
![Page 12: Defining areas using postcodes John Langley 27 th April 2007 at The Riverside Centre Derby.](https://reader036.fdocuments.in/reader036/viewer/2022062500/5697bff31a28abf838cbc4d2/html5/thumbnails/12.jpg)
Method
• Each quarter, use GIS to compare the latest NHS Postcode Dir with your boundary (“point in polygon”)
• Use the resulting file of postcodes recognising that this contains a historical dimension
• This allows linking to datasets where ‘old’ postcodes are included
![Page 13: Defining areas using postcodes John Langley 27 th April 2007 at The Riverside Centre Derby.](https://reader036.fdocuments.in/reader036/viewer/2022062500/5697bff31a28abf838cbc4d2/html5/thumbnails/13.jpg)
Problems
• NHS Postcode Directory only accurate to 100m (good enough?)
• The ‘historical’ postcodes may be lost if the Royal Mail reuses the terminated postcode (2 year period of grace?)
• ‘Postcode Drift’ – we do not yet know the extent of this – needs work?– what error does this introduce?– in which areas?– over which time period(s)?– how can we allow for it?