2011 CORRESPONDENCES PRODUCT BRIEF

Introduction

The Australian Bureau of Statistics (ABS) provides a set of correspondence files that enable users to convert data from one type of geographic area to another.

The standard correspondences available within this product are:

2011 LGA from 2011 SLA

2011 SLA from 2006 CD

2011 SLA from 2010 SLA

These files are area based correspondences. They provide a ratio of the area of overlap calculated using a GIS system. For example, a 2011 SLA may be made up of 90% of one 2010 SLA plus 10% of another 2010 SLA.

The file naming is expressed in the form of "to area" = "from area" multiplied by a ratio.


File Naming Convention for Standard Correspondences

Character and Meaning

Character	Meaning
1	C = Correspondence
2	A = Area Based Correspondence
3-6	Year of To Area
7-9	Type of To Area eg.SLA*
10	_
11-14	Year of From Area
15-17	Type of From Area eg.SLA*

* in some cases the Area type is two characters, eg "CD", adjust character count appropriately

For Example

CA2011SLA_2006CD.txt is the text file containing the information concording 2006 Census Collection Districts (CD) to 2011 SLAs based on the area correspondence principal.

Note. These files are sometimes known as a CD 2006 to SLA 2011 correspondence, but the ABS express these in the format of 2011 SLA from 2006 CD because this is the order the data appears in the file.


File Format for Standard Correspondences

Correspondence files are comma-delimited text files.

Field Name	Type
To Area Code	Character
To Area Name	Character
From Area Code	Character
From Area Name	Character
Ratio	Number
Percent	Number

Field Names will vary from file to file but are consistent in nature. The field name is constructed from the area type and date. For example the code field from the 2011 SLA file will have the name "SLA_MAINCODE_2011", and the name field from the 2011 SLA file will have the name "SLA_NAME_2011".

It is important to note the placement/ positioning convention as it is similar to the file naming convention.

Ratio - figures expressed as part of 1 - actual figures can be up to 10 decimal places.

Percentage - figures expressed as a percentage ranges from 0 to 100.


An Example

An example of how to interpret the files is described below. The example is from the area based correspondence CA2011SLA_2006CD.txt.

SLA_MAINCODE_2011	SLA_NAME_2011	CD_CODE_2006	CD_CODE_2006	RATIO	PERCENT
315102330	Cherbourg (S)	3101610	3101610	0.0003086	0.0308615
315102330	Cherbourg (S)	3101611	3101611	1	100
315102330	Cherbourg (S)	3101612	3101612	0.99942	99.942

The estimated value to 2011 SLA Cherbourg (S) data would be:

315102330 Cherbourg (S) = 3101610 data multiplied by 0.0003086

plus

315102330 Cherbourg (S) = 3101611 data multiplied by 1

plus

315102330 Cherbourg (S) = 3101612 data multiplied by 0.99942

Please remember these are area based correspondences and therefore are giving the ratio/percentage of the CDs physical area that is within the 2011 SLA's physical area. This example indicates a small misalignment where only a small amount (0.0308615%) of CD 3103610 is within the 2011 SLA of Cherbourg (S). The majority of the SLA is made up of CDs 3101611 and 3101612.

Please note the correspondence CA2011SLA_2006CD.txt has two fields containing CD_CODE_2006. This is due to the fact that CDs do not have a name, however the program needs two of the columns populated, and therefore the CD_CODE_2006 has been duplicated.


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For enquiries please email : geography@abs.gov.au