2. 7 th 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 Eric Maillé French Institute of Agricultural and Environmental Engineering Research (Cemagref) Mediterranean Agriculture and Forest Research Unit BP31 – Le Tholonet, 13612 Aix-en-Provence, France Eric Maillé French Institute of Agricultural and Environmental Engineering Research (Cemagref) Mediterranean Agriculture and Forest Research Unit BP31 – Le Tholonet, 13612 Aix-en-Provence, France

3. 7 th EC-GI & GIS Workshop, Potsdam 13-15 June 2001 Issues 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)

4. 7 th EC-GI & GIS Workshop, Potsdam 13-15 June 2001 Objectives To produce tools to assist decision-makers in land management regarding three main issues :  forest fire risk  landscape defacing  disappearance of agricultural activity To produce tools to assist decision-makers in land management regarding three main issues :  forest fire risk  landscape defacing  disappearance of agricultural activity

5. 7 th EC-GI & GIS Workshop, Potsdam 13-15 June 2001 Hypothesis 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.

6. 7 th EC-GI & GIS Workshop, Potsdam 13-15 June 2001 Two 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

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

8. 7 th EC-GI & GIS Workshop, Potsdam 13-15 June 2001 Marseille

9. 7 th EC-GI & GIS Workshop, Potsdam 13-15 June 2001 Aix-en- Provence Marseille Vitrolles -Etang de Berre District 1 District 2 024 km IGN Scan100 ®

10. 7 th EC-GI & GIS Workshop, Potsdam 13-15 June 2001 Aerial 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

11. 7 th EC-GI & GIS Workshop, Potsdam 13-15 June 2001 Outputs 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)

12. 7 th EC-GI & GIS Workshop, Potsdam 13-15 June 2001 An example of synchronic maps

13. 7 th EC-GI & GIS Workshop, Potsdam 13-15 June 2001 An example of a diachronic map

14. 7 th EC-GI & GIS Workshop, Potsdam 13-15 June 2001 Area variations Figures stemming from synchronic covers Figures stemming from topologically crossed covers

15. 7 th EC-GI & GIS Workshop, Potsdam 13-15 June 2001 Structural analysis: complexity assessment

16. 7 th EC-GI & GIS Workshop, Potsdam 13-15 June 2001 Shape complexity indicators Example : the Patton indicator (equals 1 for any disk) Relationship indicators between land categories Example: interface length Patch and relationship indicators

17. 7 th EC-GI & GIS Workshop, Potsdam 13-15 June 2001 An interlocking relationship indicator For 2 polygons with S 1 and S 2 surfaces, joined by the interface length L 1-2 This equals 1 for 2 squares of equal surfaces, joined on one side For a whole cover: I (AB) : indicator of interlocking between category A land and category B land n i(AB) : number of arcs separating patches of category A land from patches of category B land L i(AB) : length of arcs number i (AB) separating one patch of category A land from one patch of category B land n A : number of patches of category A land n B : number of patches of category B land S pA : surface of patch number p A of category A land S pB : surface of patch number p B of category B land

18. 7 th EC-GI & GIS Workshop, Potsdam 13-15 June 2001 Parcelling –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)

19. 7 th EC-GI & GIS Workshop, Potsdam 13-15 June 2001 1998 1996 Interlocking indicators evolution (District 1) 0 200 400 Interlocking indicators evolution (District 2) 0 200 400 Farming/natural Farming/urban Natural /urban 1968 1964 0 10 20 30 40 50 196819851998 years Interfaces length per hectare (District 1) 0 10 20 30 40 50 19641996 years Interfaces length per hectare (District 2) Km/ha Natural/urban Farming/natural Farming/urban Farming land / natural land (forest) interface Farming land / urban land interface Natural land (forest) / urban land interface Farming land / natural land (forest) interface Farming land / urban land interface Natural land (forest) / urban land interface District 1 District 2 Interface length Interlocking

20. 7 th EC-GI & GIS Workshop, Potsdam 13-15 June 2001 Parcelling

21. 7 th EC-GI & GIS Workshop, Potsdam 13-15 June 2001 A 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

22. 7 th EC-GI & GIS Workshop, Potsdam 13-15 June 2001 Next steps 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)