7th EC-GI & GIS Workshop, Potsdam 13-15 June 2001

Quantitative diachronic spatial analysis using GISs to assist decision-makers in land management in

periurban areas

As applied to two French periurban districts included in the Aix-Marseille conurbation

Quantitative diachronic spatial analysis using GISs to assist decision-makers in land management in

periurban areas

As applied to two French periurban districts included in the Aix-Marseille conurbation

Eric MailléFrench Institute of Agricultural and Environmental Engineering Research (Cemagref)

Mediterranean Agriculture and Forest Research UnitBP31 – Le Tholonet, 13612 Aix-en-Provence, France

Eric MailléFrench Institute of Agricultural and Environmental Engineering Research (Cemagref)

Mediterranean Agriculture and Forest Research UnitBP31 – Le Tholonet, 13612 Aix-en-Provence, France

7th EC-GI & GIS Workshop, Potsdam 13-15 June 2001

IssuesIssues

• A low-density urbanisation process leading to the emergence of complex lands

» forest fire risk

» landscape defacing

» disappearance of agricultural activity

» biodiversity and other environmental issues

» transport, infrastructure costs,

» etc.

• decision-makers need tools to properly use legal zonings for land management (especially French Local Urbanisation Plan - PLU)

• A low-density urbanisation process leading to the emergence of complex lands

» forest fire risk

» landscape defacing

» disappearance of agricultural activity

» biodiversity and other environmental issues

» transport, infrastructure costs,

» etc.

• decision-makers need tools to properly use legal zonings for land management (especially French Local Urbanisation Plan - PLU)

7th EC-GI & GIS Workshop, Potsdam 13-15 June 2001

ObjectivesObjectives

• To produce tools to assist decision-makers in land management regarding three main issues :

forest fire risk landscape defacingdisappearance of agricultural activity

• To produce tools to assist decision-makers in land management regarding three main issues :

forest fire risk landscape defacingdisappearance of agricultural activity

7th EC-GI & GIS Workshop, Potsdam 13-15 June 2001

HypothesisHypothesis

Farming land use possibilities, landscape quality, and forest fire risk are not only

related to the surface ratio between different land types, but also to spatial structures.

Farming land use possibilities, landscape quality, and forest fire risk are not only

related to the surface ratio between different land types, but also to spatial structures.

7th EC-GI & GIS Workshop, Potsdam 13-15 June 2001

Two main stepsTwo main steps

• Creating a diachronic cartographic depiction of land cover transformation on a GIS by interpreting aerial photographs taken at different periods– Generating one GIS cover for each period

– Crossing the different covers

– Producing synchronic and diachronic maps

• Analysing spatial transformations– measuring area evolutions

– calculating indicators of structural transformations

• Creating a diachronic cartographic depiction of land cover transformation on a GIS by interpreting aerial photographs taken at different periods– Generating one GIS cover for each period

– Crossing the different covers

– Producing synchronic and diachronic maps

• Analysing spatial transformations– measuring area evolutions

– calculating indicators of structural transformations

7th EC-GI & GIS Workshop, Potsdam 13-15 June 2001

On a local scaleOn a local scale

• Two districts included in the Aix-Marseille conurbation (France, Region: Provence-Alpes-Côte d ’Azur, Department: Bouches-du-Rhône)

» District 1: 3682 ha

» District 2: 1086 ha

• Two districts included in the Aix-Marseille conurbation (France, Region: Provence-Alpes-Côte d ’Azur, Department: Bouches-du-Rhône)

» District 1: 3682 ha

» District 2: 1086 ha

7th EC-GI & GIS Workshop, Potsdam 13-15 June 2001

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Roma

Paris

Dublin BerlinLondon

Madrid

Lisboa

Vienna

Athinai

HelsinkiStockholm

Amsterdam

Kobenhavn

Bruxelles

Luxembourg

Marseille

Rh

ôn

e

Rhone-Alpes

Languedoc-Roussillon

Provence-Alpes-Cote d'Azur

ITALY

Rhone

LYON

TORINO

MARSEILLE

NICE

CANNES

GRENOBLE

NIMES

AVINGON

ARLES

GAP

AOSTA

DIGNE

CUNEO

BERRE-L'ETANGDRAGUIGNAN

TOULON

MONTPELLIER MONACOAIX-EN-PROVENCE

FOS

7th EC-GI & GIS Workshop, Potsdam 13-15 June 2001

Aix-en-Provence

Marseille

Vitrolles -Etang

de Berre

District 1

District 2

0 2 4 km

IGN Scan100®

7th EC-GI & GIS Workshop, Potsdam 13-15 June 2001

Aerial photograph interpreting and cartographyAerial photograph interpreting and cartography

• Periods» 3 periods for district 1: 1968, 1985, 1998

» 2 periods for district 2: 1964, 1996

• A three levels nomenclature» first level: land use (urban, farming, natural)

» second level: land appearance (grass, shrubs, trees, complex lands, etc.)

» third level: vegetation and buildings densities

• Technical processes: » For (old) small-size photographs: scanning, manual

interpretation on screen, rectification and assembling

» For (recent) large-size photographs (A0): plan tracing, digitising on a digitizer table, rectification

• Periods» 3 periods for district 1: 1968, 1985, 1998

» 2 periods for district 2: 1964, 1996

• A three levels nomenclature» first level: land use (urban, farming, natural)

» second level: land appearance (grass, shrubs, trees, complex lands, etc.)

» third level: vegetation and buildings densities

• Technical processes: » For (old) small-size photographs: scanning, manual

interpretation on screen, rectification and assembling

» For (recent) large-size photographs (A0): plan tracing, digitising on a digitizer table, rectification

7th EC-GI & GIS Workshop, Potsdam 13-15 June 2001

OutputsOutputs

• one vectorial GIS cover for each period cartography synchronic maps

quantitative analysis (areas, structures)

• crossings: diachronic covers Cartography diachronic maps

quantitative analysis (areas)

• one vectorial GIS cover for each period cartography synchronic maps

quantitative analysis (areas, structures)

• crossings: diachronic covers Cartography diachronic maps

quantitative analysis (areas)

7th EC-GI & GIS Workshop, Potsdam 13-15 June 2001

An example of synchronic mapsAn example of synchronic maps

7th EC-GI & GIS Workshop, Potsdam 13-15 June 2001

An example of a diachronic mapAn example of a diachronic map

7th EC-GI & GIS Workshop, Potsdam 13-15 June 2001

Area variationsArea variations

District 1 District 2Hectares 1968 1998 Variation Variation

Rate1964 1996 Variation Variation

Rate

Agricultural lands 1310 (36%) 703 (19%) -607 (17%) -46% 472 (43%) 157 (14%) -316 (29%) -67%

Natural lands (includingforest) 2174 (59%) 1987 (54%) -186 (5%) -9% 595 (55%) 716 (66%) +121 (11%) +20%

Urban lands 149 (4%) 936 (25%) +786 (21%) +526% 19 (2%) 205 (19%) +186 (17%) +979%

District 1 (1968-1998) District 2 (1964-1996)Hectares Agricultu

ral landsnaturallands

Crossingerrors

Total Agricultural lands

Naturallands

Crossingerrors

Total

New urban areaon…

521(65%)

281(35%)

-16 786(100%)

167 (83%)

32(17%)

-13 186(100%)

Natural landsadvance

> +79 (crossing errors maximised)> +3.6% of the initial natural lands area

> +140 (crossing errors maximised)> +23% of the initial natural lands area

•Figures stemming from synchronic covers

•Figures stemming from topologically crossed covers

7th EC-GI & GIS Workshop, Potsdam 13-15 June 2001

Structural analysis:complexity assessment

Structural analysis:complexity assessment

7th EC-GI & GIS Workshop, Potsdam 13-15 June 2001

•Shape complexity indicatorsExample : the Patton indicator (equals 1 for any disk)

•Shape complexity indicatorsExample : the Patton indicator (equals 1 for any disk)

urfaceS

PerimeterP

*2

•Relationship indicators between land categoriesExample: interface length

•Relationship indicators between land categoriesExample: interface length

Patch and relationship indicatorsPatch and relationship indicators

7th EC-GI & GIS Workshop, Potsdam 13-15 June 2001

An interlocking relationship indicatorAn interlocking relationship indicator

For 2 polygons with S1 and S2 surfaces, joined by the interface length L1-2

This equals 1 for 2 squares of equal surfaces, joined on one side

21)21(

2

SSLI

For a whole cover:

A

A

B

B

BA

BAABi

AB

AB n

p

n

p

pp

n

i

iAB

SS

nnLI

1 1

1(

)(

)(

)

)(

I(AB): indicator of interlocking between category A land and category B landni(AB): number of arcs separating patches of category A land from patches of category B landLi(AB): length of arcs number i(AB) separating one patch of category A land from one patch of category B landnA: number of patches of category A landnB: number of patches of category B landSpA: surface of patch number pA of category A landSpB: surface of patch number pB of category B land

7th EC-GI & GIS Workshop, Potsdam 13-15 June 2001

ParcellingParcelling

– For each land category (regardless of the others):» number of patches and mean area

– For each land category in relation to the others:» “Islands” detection (number of islands and

mean area)

– For each land category (regardless of the others):» number of patches and mean area

– For each land category in relation to the others:» “Islands” detection (number of islands and

mean area)

7th EC-GI & GIS Workshop, Potsdam 13-15 June 2001

19981996

Interlocking indicators evolution (District 1)

0

200

400Interlocking indicators

evolution (District 2)

0

200

400Farming/natural

Farming/urbanNatural /urban

1968 1964

0

10

20

30

40

50

1968 1985 1998years

Interfaces length per hectare (District 1)

0

10

20

30

40

50

1964 1996years

Interfaces length per hectare (District 2)

Km/ha Km/ha

Natural/urban

Farming/natural

Farming/urban

Farming land / natural land (forest) interfaceFarming land / urban land interface

Natural land (forest) / urban land interface

Farming land / natural land (forest) interfaceFarming land / urban land interface

Natural land (forest) / urban land interface

District 1 District 2In

terf

ace

leng

thIn

terl

ocki

ng

7th EC-GI & GIS Workshop, Potsdam 13-15 June 2001

ParcellingParcelling

Number of patches (mean area,ha)

District 1 District 2

1968 1998 1964 1996Farming land 31 (42.3) 96 (7.3) 4 (118.0) 88 (1.8)Natural land 16 (135.8) 27 (73.6) 30 (19.8) 35 (20.5)Urban land 58 (2.6) 67 (14.0) 40 (0.5) 186 (1.1)“Islands” of urban landinside farming land

36 (0.6 ha) 18 (0.5 ha) 1 (1.2 ha) 13 (0.1ha)

“Islands” of farming landinside urban land

1 (1.8 ha) 24 (3 ha) 1 (3.9 ha) 16 (1.3ha)

“Islands” of urban landinside natural land

1 (1.7ha) 26 (1.3 ha) 14 (1.4 ha) 119 (0.1ha)

7th EC-GI & GIS Workshop, Potsdam 13-15 June 2001

A few limitsA few limits

• Results depend on the photograph interpretation

• A full arc and polygon topology is needed (except

arc directions)

• Indicators only make sense in comparative

processes

• Several possible indicators for the same structural

characteristic

• Results depend on the photograph interpretation

• A full arc and polygon topology is needed (except

arc directions)

• Indicators only make sense in comparative

processes

• Several possible indicators for the same structural

characteristic

7th EC-GI & GIS Workshop, Potsdam 13-15 June 2001

Next stepsNext steps

• To relate space indicators to farming system functioning and transformations (qualitative)

• To relate space indicators to farming system functioning and transformations (qualitative)

At the planning stage...

• To correlate space indicators to forest fire risk indicators (quantitative)

• Simulation: to predict future land transformations• To change work scale (using remote sensing)

• To correlate space indicators to forest fire risk indicators (quantitative)

• Simulation: to predict future land transformations• To change work scale (using remote sensing)