1. GRIDS AS USEFUL TOOL FOR REBUILDING TIME SERIES
Claude GRASLAND (Univ. Paris Diderot)
Nicolas LAMBERT (CNRS-RIATE)
Hélène MATHIAN (CNRS- Géographie-cités)

2. SPECIFIC PROBLEM
HOW IS IT POSSIBLE TO ANALYZE EVOLUTIONS
WHEN TERRITORIAL DIVISIONS ARE CHANGING ?

3. HOW IS IT POSSIBLE TO COMBINE DATA AVAILABLE
GENERAL PROBLEM
GEOM1
GEOM1 x GEOM2
GEOM2
HOW IS IT POSSIBLE TO COMBINE DATA AVAILABLE
ON TWO DIFFERENT GEOMETRIES ?

4. SOLUTION n°1 : TRANSFER DATA BY GRID SOLUTION
V1_GRID
GEOM1xV1
Auxilliary
attribute
GRID
GEOM2xV2

5. SOLUTION n°2 : GRIDDING + SMOOTHING
V1_GRID
GEOM1xV1
POT_V1
Ancillary
variable
GRID
POT_V2 / POT_V1
V2_GRID
GEOM2xV2
POT_V2

6. GRIDDING + SMOOTHING

7. TEST AREA : South-Western France

8. OBJECTIVE : Annual growth rate of population 1990-2006
GEOM1
55 Arrondissements
GEOM2
52 Zones d’emploi
???
???

9. AN EXACT BUT NOT INTERESTING SOLUTION :
Aggregation at first common level

10. ANCILLARY VARIABLE 100 000 Grid points Grid of population 1km x 1km
From EEA
ANCILLARY
VARIABLE
Grid points

11. ESTIMATION OF TARGET INDICATOR
POP90 / ARRD
POP90 /GRID
POT (POP90)
Gauss 20 km
POP00/GRID
ANNUAL GROWTH
RATE
Gauss 20 km
POP06/ GRID
POP06 / ZEMP
POT (POP06)
Gauss 20 km

12. ESTIMATION OF RESIDUAL « NOISE »
POP06 / ARRD
POP06/GRID*
POT (POP06)*
Gauss 20 km
POP00/GRID
POT(POP06) *
____________
POT (POPO6)
POP06/GRID
POP06 / ZEMP
POT (POP06)
Gauss 20 km

13. Smooth 10 km GOOD SPATIAL RESOLUTION … … BUT HIGH LEVEL OF NOISE
Increase of population
Noise introduced by the method
(%)
0.25
0.5
0.75
1.0
-5%
-1%
+1%
+5%

14. Smooth 40 km LOW SPATIAL RESOLUTION … … BUT LOW LEVEL OF NOISE
Increase of population
Noise introduced by the method
(%)
0.25
0.5
0.75
1.0
-5%
-1%
+1%
+5%

15. Smooth 20 km GOOD COMPROMISE BETWEEN SPATIAL RESOLUTION AND NOISE
Increase of population
Noise introduced by the method
(%)
0.25
0.5
0.75
1.0
-5%
-1%
+1%
+5%

16. SYNTHESIS : Signal & Noise
Max Noise < 5%
Mean Noise < 1%
Gaussian Smooth
> 22 km

17. CONCLUSION & PERSPECTIVES
Smooth + Grid
CONCLUSION & PERSPECTIVES

18. Longer Time Series

19. Multilevel spatial analysis

20. Cross Border Analysis

21. Modifiable Area Unit Progress

22. Thank you for your attention !
Grasland, Mathian, Vincent, 2000,
Statistical Journal of UN-ECE
Grasland, Madelin, 2007,
ESPON 3.4.3, MAUP