GIS Report - Birmingham Retail

Cobain Schofield

Retail Catchment Analysis in the West Midlands

Basic Buffer Catchment Analysis

Figure 1 shows a basic buffer map with primary and secondary catchment areas centred on each

retail centre within the West Midlands. The buffers are based on simple Euclidean distances of

1,500m for the primary catchments and 3,000m for the secondary catchments – these distances

are based on walking times of 15 and 30 minutes respectively with an average walking speed of

3.1mph (Aspelin, 2005). This method assumes uniformity in all directions and a constant walking

speed without obstacles. It also assumes that each retail centre has an identical catchment, which

is not the case in reality. Suggested catchment areas were not used owing to overcrowding on the

map and a loss of visual clarity.

Figure 1 – Basic primary and secondary catchment areas for each retail centre in the West

Midlands study area.

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Birmingham

Wolverhampton

Merry Hill Centre

Bilston

Tamworth

Harborne

Aldridge

Halesowen

ErdingtonPerry Barr

Northfield

Bromsgrove

Stourbridge

Kings Heath

Shirley, Solihull

Ventura Road Retail Park, Bitterscote

Solihull

Redditch

Coventry

West Bromwich

Sutton Coldfield

±

0 3 6 9 121.5Miles

Legend

Retail Centre Hierarchy Ranks

!( 1 - Major Retail Location

!( 2

!( 3

!( 4 - Minor Retail Location

Primary Catchment

Secondary Catchment

Birmingham LSOAs

Cobain Schofield

Ranked Buffer Catchment Analysis

Figure 2 acknowledges that each different type of retail centre will attract people from different

areas for a range of different reasons including store type and diversity, as discussed by Steiner

(1998). However, these ranked catchments still assume identical catchment properties for each

rank category.

Figure 2 – Basic primary and secondary catchments ranked according to Table 1

Table 1 – Catchment radiuses for each retail centre rank, calculated according to Dramowicz (n.d)

Primary Catchment Radius (m) Secondary Catchment Radius (m)

Rank 1 8000 3600

Rank 2 5000 2250

Rank 3 3000 1350

Rank 4 1500 675

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Birmingham

Wolverhampton

Merry Hill Centre

Bilston

Tamworth

Harborne

Aldridge

Halesowen

ErdingtonPerry Barr

Northfield

Bromsgrove

Stourbridge

Kings Heath

Shirley, Solihull


Solihull

Redditch

Coventry

West Bromwich

Sutton Coldfield

±

0 3 6 9 121.5Miles

Legend



!( 2

!( 3


Primary Catchment (Ranked)

Secondary Catchment (Ranked)

Birmingham LSOAs

Cobain Schofield

Applying the Huff Model to Establish Retail Catchments

The Huff Model of Retail Gravitation (1964) was used to estimate catchments around each retail

centre based on the LSOA map of Birmingham. Some parameters were supplied, although some

were edited according to Huff (2003). The tertiary parameter value was altered from 0.2 to 0.25 to

maintain a 50% decrease in value from primary to secondary to tertiary. This increased the tertiary

catchment area from 16.7km2 to 18.3km2. This shows the tertiary catchment extending throughout

the map rather than being solely based around the north western quadrant.

This model does not rely on arbitrary Euclidean distances, but it does not differentiate between

each town centre; it is not possible to differentiate and identify all catchments, particularly in the

more densely populated areas around Birmingham.

Figure 3 – Basic Huff Model showing primary, secondary and tertiary catchments across the study

area.

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Birmingham

Wolverhampton

Merry Hill Centre

Bilston

Tamworth

Harborne

Aldridge

Halesowen

ErdingtonPerry Barr

Northfield

Bromsgrove

Stourbridge

Kings Heath

Shirley, Solihull


Solihull

Redditch

Coventry

West Bromwich

Sutton Coldfield

±

0 3 6 9 121.5Miles

Legend



!( 2

!( 3


Huff Model Catchments

Tertiary Catchment

Secondary Catchment

Primary Catchment

Cobain Schofield

Multiple Attribute Huff Model

Figure 4 shows the same data as Figure 3 but with each catchment coloured differently to help

distinguish each retail centre. The lightest colours around each retail centre show tertiary

catchments, while the darker colours are primary catchments. The predominant Khaki colour

covering much of the map represents Birmingham’s secondary catchment; however this is

questionable given the extent of the expanse.

Figure 4 – Huff Model showing individual catchments around each retail centre

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Birmingham

Wolverhampton

Merry Hill Centre

Bilston

Tamworth

Harborne

Aldridge

Halesowen

ErdingtonPerry Barr

Northfield

Bromsgrove

Stourbridge

Kings Heath

Shirley, Solihull


Solihull

Redditch

Coventry

West Bromwich

Sutton Coldfield

±

0 3 6 9 121.5Miles

Legend



!( 2

!( 3



Tertiary Catchment (Lightest)

Secondary Catchment

Primary Catchment (Darkest)

Cobain Schofield

Combined Ranked Buffer and Huff Catchments

Figure 5 shows the disparity between the catchment areas calculated using the Huff Model and

those generated through the ranked buffer methods in Figure 2. This is because the Huff Model

accounts for factors which differ between each retail centre.

Figure 5 – Combined catchment map comparing the extent of ranked buffer zones from Figure 2

with catchments generated by the Huff Model in Figure 3

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Birmingham

Wolverhampton

Merry Hill Centre

Bilston

Tamworth

Harborne

Aldridge

Halesowen

ErdingtonPerry Barr

Northfield

Bromsgrove

Stourbridge

Kings Heath

Shirley, Solihull


Solihull

Redditch

Coventry

West Bromwich

Sutton Coldfield

±

0 3 6 9 121.5Miles

Legend



!( 2

!( 3




Tertiary Catchment (Lightest)

Secondary Catchment

Primary Catchment (Darkest)

Cobain Schofield

Generating Catchments based on the Road Network

Road Network data for the West Midlands was obtained from Edina and a basic road network was

established. Catchments were generated based on the distance from each retail centre by road

only. As mentioned in ESRI’s guide to using OS ITN (2007), the road network data is “limited by

the lack of speed limit information on roads and inability to differentiate between urban and

rural areas”. The dataset is also absent of road direction data, traffic control systems and public

transport networks.

There are broken links in road junctions on the dataset which cause errors in the processing, such

as the ~25% empty area north east of Wolverhampton, as detailed in Figure 7 on Page 7. These

are apparently caused by obstacles such as railway lines (Figure 8).

Figure 6 – Rank 1 retail centres with catchments derived from the road network.

!(!(

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Birmingham

Wolverhampton

Merry Hill Centre

±

0 3 6 9 121.5Miles

Legend


!( Rank 1 Retail Centre

Rank 1 Roads

Rank 1 Catchments

Birmingham LSOAs

Cobain Schofield

Figure 7 – Broken road links 0.25 miles outside Wolverhampton hamper the generation of road

network catchments

Figure 8 – Railway lines appear to be causing broken links in the road network in Figure 7

!(Wolverhampton

±

0 0.25 0.5 0.75 10.125Miles

Legend


Rank

!(1 - Major Retail Location

Birmingham LSOAs

Rank 1 Roads

Rank 1 Catchments

Credit: Google Maps

A on Figure 7

B on Figure 7

A

B

Cobain Schofield

Figure 9 - Rank 2 retail centres with catchments derived from the road network.

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Walsall

Solihull

Redditch

Coventry

West Bromwich

Sutton Coldfield

±

0 3 6 9 121.5Miles

Legend


!( Rank 2 Retail Centre

Rank 2 Roads

Rank 2 Catchments

Birmingham LSOAs

Cobain Schofield

Figure 10 – Combined Road Network catchments for retail centres ranked 1 to 4

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Birmingham

Wolverhampton

Merry Hill Centre

Bilston

Tamworth

Harborne

Aldridge

Halesowen

ErdingtonPerry Barr

Northfield

Bromsgrove

Stourbridge

Kings Heath

Shirley, Solihull


Solihull

Redditch

Coventry

West Bromwich

Sutton Coldfield

±

0 3 6 9 121.5Miles

Legend



!( 2

!( 3


Birmingham LSOAs

Rank 1 Roads

Rank 1 Catchments

Rank 2 Roads

Rank 2 Catchments

Rank 3 Roads

Rank 3 Catchments

Rank 4 Roads

Rank 4 Catchments

Cobain Schofield

Figure 11 shows that the higher ranked retail centres have road network catchments which extend

as far as, or almost as far as the secondary buffer catchments when the same distances are used.

The smaller centres may not extend so far, as road networks are not as dense nor direct as those

in the larger towns and cities Therefore, one must travel further along roads before reaching the

edge of the buffer catchment.

Figure 11 - Combined catchment map comparing the extent of ranked buffer zones from Figure 2

with catchments generated by the road network.

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Birmingham

Wolverhampton

Merry Hill Centre

Bilston

Tamworth

Harborne

Aldridge

Halesowen

ErdingtonPerry Barr

Northfield

Bromsgrove

Stourbridge

Kings Heath

Shirley, Solihull


Solihull

Redditch

Coventry

West Bromwich

Sutton Coldfield

±

0 3 6 9 121.5Miles

Legend



!( 2

!( 3


Birmingham LSOAs


Rank 1 Roads

Rank 1 Catchments

Rank 2 Roads

Rank 2 Catchments

Rank 3 Roads

Rank 3 Catchments

Rank 4 Roads

Rank 4 Catchments

Cobain Schofield

Data Sources

All maps are based on Edina Census Geography shape files.

1 Birmingham Shape Files (mapping): Edina “Census Geography” http://census.edina.ac.uk

2 OS MasterMap ITN Layer (mapping): Edina Digimap “OS MasterMap ITN” http://digimap.edina.ac.uk

Colouration of all maps is based on Cynthia et al (2003) so as not to discriminate against those

with vision impediments or colour blindness.

References

Aspelin, K. (2005) “Establishing Pedestrian Walking Speeds”. Portland State University. Available

at: http://www.westernite.org/datacollectionfund2005/psu_ped_summary.pdf; Accessed: 24th

March 2015

Cynthia, A. (2003) “A transition in Improving Maps: The ColorBrewer Example” in U.S Report to

the International Cartographic Association, special issue of Cartography and Geographic

Information Science 30(2);155-158.

Cynthia, A. and Mark, A. (2003) “ColorBrewer.org: An Online Tool for Selecting Color Schemes

for Maps”. The Cartographic Journal 40(1):27-37.

Dramowicz, E. (n.d) “Retail Trade Analysis Using the Huff Model”. Directions Magazine. No

published date available. Available online at: http://www.directionsmag.com/entry/retail-trade-area-

analysis-using-the-huff-model/123411; Last accessed: 24th March 2015

ESRI (2007) “Using OS MasterMap Intergrated Transport Network (ITN) Layer with ArcGIS: An

ESRI (UK) White Paper”. Published by ESRI (UK) Ltd, Buckinghamshire, UK. Version 2.0.

Google Maps – Map of Wolverhampton utilised in Figure 8. Available online at:

http://goo.gl/d6hNpG; Last accessed: 27th March 2015

Huff, D. (1964) “Defining and Estimating a Trading Area”. Journal of Marketing, American

Marketing Association. Volume 28 (July 1964), pp. 34-38

Huff, D. (2003) “Parameter Estimation in the Huff Model”. ArcUser, October-December 2003

Edition, 34-36

Steiner, R. (1998) “Traditional Shopping Centres”. ACCESS Magazine. University of California

Transportation Centre, 4th January 1998.

GIS Report - Birmingham Retail

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