1216.0.15.002 - Australian Standard Geographical Classification (ASGC) Concordances, 01 Jul 2008  
ARCHIVED ISSUE Released at 11:30 AM (CANBERRA TIME) 17/07/2008   
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2008 ASGC AREA BASED CONCORDANCES PRODUCT BRIEF

Introduction

The Australian Bureau of Statistics (ABS) has developed several concordance products that enable users to convert data for one type of geographic area to another.

There are two types of concordances that the ABS produces, a population based concordance and an area based concordance. This publication contains area based concordances only.

The area based concordance expresses the percentage of the "From" area contained within the "To" area. The population weighted concordance expresses the percentage of the "From" area's population contained within the "To" area. Population weighted concordances ABS Postal Area Concordances, August 2006 (cat. no. 2905.0.55.001) are available from the ABS website and are only available for geographies from the same Census years.

The Area Based concordance

The area based concordance is based on the area of the "From" area contained in the "To" Area. This is calculated using a GIS system.

In the area based concordance there may be situations where the boundaries do not align perfectly and a very, very small percentage of one area is contained in another. In these cases if the percentage calculated is below 0.001 percent then the figure is set to zero (0), similarly if the percentage is greater than 99.999 percent the value is set to 1.0.

File Format

The file naming convention is :

Character and Meaning

      1 "C" for Concordance
      2 "A" for Area Based Concordance
      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

CA2008SLA_2006CD.txt is the text file containing the information concording 2006 Census Collection Districts to 2008 SLAs based on the area concordance principal.

The "From Area" and "To Area" naming convention is "Mathematically based"

"To Area" = "From Area" multiplied by ratio

105051100 = 123456565 * 0.505

105051200 = 123456565 * 0.595

Concordance 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
      Percentage 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 2008 SLA file will have the name "SLA_2008_Code", and the name field from the 2008 SLA file will have the name "SLA_2008_Name". It is important to note the placement/ positioning convention as it is similar to the file naming convention

Percentage - figure expressed as a percentage ranges from 100 to 0

Ratio - figures expresses as part of 1 - actual figures can be up to 10 decimal places and are expressed in mathematical terms - 4.77810788750317e-04 which is 0.000477810788750317

Foe example:

"SLA_2008_Code","SLA_2008_Name","CD_2006_Code","CD_2006_Name","Ratio","Percent"
      105051100,Botany Bay (C),1421807,1421807, 1, 100
      105051100,Botany Bay (C),1421806,1421806, 1, 100
      105051100,Botany Bay (C),1421805,1421805, 1, 100
      105051100,Botany Bay (C),1421804,1421804, 1, 100
      105051100,Botany Bay (C),1421809,1421809, 1, 100

Or

"SLA_2008_Code","SLA_2008_Name","CD_2006_Code","CD_2006_Name","Ratio","Percent"
      105051100,Botany Bay (C),1421909,1421909, .999886150596782, 99.9886150596782
      105051100,Botany Bay (C),1421808,1421808, .999993652481281, 99.9993652481281
      105051100,Botany Bay (C),1421907,1421907, .999972553418185, 99.9972553418185
      105051100,Botany Bay (C),1421904,1421904, .999994750369691, 99.9994750369691
      105051100,Botany Bay (C),1421903,1421903, .999986839499272, 99.9986839499272

The "From Area" and "To Area" naming convention is "Mathematically based"

"To Area" = "From Area" multiplied by ratio
      105051100 = 105055200* 0. 97.95
      105051100 = 105055200* 0.0001
      105051200 = 105106550 * 0.0004

Copyright Commonwealth of Australia administered by the ABS.

For enquires please contact the ABS Geography Section, see details below.

ABS Geography Section

Email: geography@abs.gov.au

July 2008