NTTS 2009 Brussels February 20 1 A Downscaled Population Density Map of the EU from Commune Data and...
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Transcript of NTTS 2009 Brussels February 20 1 A Downscaled Population Density Map of the EU from Commune Data and...
![Page 1: NTTS 2009 Brussels February 20 1 A Downscaled Population Density Map of the EU from Commune Data and Land Cover Information Javier.gallego@jrc.it NOTES.](https://reader035.fdocuments.us/reader035/viewer/2022062417/55152dee5503465e608b5895/html5/thumbnails/1.jpg)
NTTS 2009 Brussels February 20 1
A Downscaled Population Density Map of the EU from Commune Data and Land Cover Information
![Page 2: NTTS 2009 Brussels February 20 1 A Downscaled Population Density Map of the EU from Commune Data and Land Cover Information Javier.gallego@jrc.it NOTES.](https://reader035.fdocuments.us/reader035/viewer/2022062417/55152dee5503465e608b5895/html5/thumbnails/2.jpg)
NTTS 2009 Brussels February 20 2
In most countries, population data are available for public use only per administrative unit (commune)
• In many cases this may be insufficient for geographical analysis. – It depends on the size of the geographic units and the
scale of the event under assessment. – Population hit by a flood– Population in the 65 decibel contour of airports– Population at a distance > 2 km of the closest primary
school.
In some countries, population data exist for 1 km grids– Bottom-up approach (much better..)
Rationale
![Page 3: NTTS 2009 Brussels February 20 1 A Downscaled Population Density Map of the EU from Commune Data and Land Cover Information Javier.gallego@jrc.it NOTES.](https://reader035.fdocuments.us/reader035/viewer/2022062417/55152dee5503465e608b5895/html5/thumbnails/3.jpg)
NTTS 2009 Brussels February 20 3
Population density downscalingPopulation density downscalingPopulation density downscalingPopulation density downscaling
•Starting data: Population per commune and CORINE Land Cover. •Result: Approximate population density with 1 ha resolution (GIS grid)
+
=
![Page 4: NTTS 2009 Brussels February 20 1 A Downscaled Population Density Map of the EU from Commune Data and Land Cover Information Javier.gallego@jrc.it NOTES.](https://reader035.fdocuments.us/reader035/viewer/2022062417/55152dee5503465e608b5895/html5/thumbnails/4.jpg)
NTTS 2009 Brussels February 20 4
CORINE Land Cover
Land cover map from photo-interpreted Landsat-TM images
• 44 classes– Urban dense– Urban discontinuous– ……
• Minimum mapping unit: 25 ha. – Smaller patches swallowed by
dominant class– heterogeneous classes if no one is
dominant (~10% of the total area)
• For this exercise, simplified nomenclature of 9 classes
![Page 5: NTTS 2009 Brussels February 20 1 A Downscaled Population Density Map of the EU from Commune Data and Land Cover Information Javier.gallego@jrc.it NOTES.](https://reader035.fdocuments.us/reader035/viewer/2022062417/55152dee5503465e608b5895/html5/thumbnails/5.jpg)
NTTS 2009 Brussels February 20 5
A simple model for downscaling
• Xm : population in commune m
• Scm : area of land cover type c in commune m.
• Ycm : density of population for land cover type c in commune m. Inside each commune Ycm is assumed to be proportional to given coefficients Uc for each
land cover type: • If we know Uc , Wm are computed to respect the total population of the
commune
• Problem: estimating reasonable coefficients Uc
mccm WUY
cccm
mm US
XW
cccm
mccm US
XUY
![Page 6: NTTS 2009 Brussels February 20 1 A Downscaled Population Density Map of the EU from Commune Data and Land Cover Information Javier.gallego@jrc.it NOTES.](https://reader035.fdocuments.us/reader035/viewer/2022062417/55152dee5503465e608b5895/html5/thumbnails/6.jpg)
NTTS 2009 Brussels February 20 6
Version 1 of the downscaling
Estimating Uc with an iterative algorithm:
1. Pretend for a moment that population is known only per region (not per commune)
2. Downscale with a provisional set of coefficients
3. Compute the population that would be attributed to each commune X*
m
4. Compare each X*m with the known population Xm and compute a
disagreement index
5. Modify Uc to reduce the disagreement (ask paper for details)
6. Turn to step 2 or stop if modification very small
![Page 7: NTTS 2009 Brussels February 20 1 A Downscaled Population Density Map of the EU from Commune Data and Land Cover Information Javier.gallego@jrc.it NOTES.](https://reader035.fdocuments.us/reader035/viewer/2022062417/55152dee5503465e608b5895/html5/thumbnails/7.jpg)
NTTS 2009 Brussels February 20 7
LUCAS 2001/2003 (Land Use/Cover Area-frame Survey)
• Managed by Eurostat (Common specifications for EU15 )
• nomenclature Land cover (57 classes) * Land use (14 classes)
• The land Use “residential” gives information useful to assess the density of buildings in CLC non-urban classes.
• The residential area is used as proxy of the population density in CLC non-urban areas.
Introducing LUCAS data
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LUCAS: residential points in non-urban CLC2000 classes
CLC2000 class of the LUCAS point# Other artificial# Agriculture# Heterogeneous# Forest# Natural vegetation
![Page 8: NTTS 2009 Brussels February 20 1 A Downscaled Population Density Map of the EU from Commune Data and Land Cover Information Javier.gallego@jrc.it NOTES.](https://reader035.fdocuments.us/reader035/viewer/2022062417/55152dee5503465e608b5895/html5/thumbnails/8.jpg)
NTTS 2009 Brussels February 20 8
% of LUCAS residential points for different CLC2000 classes
![Page 9: NTTS 2009 Brussels February 20 1 A Downscaled Population Density Map of the EU from Commune Data and Land Cover Information Javier.gallego@jrc.it NOTES.](https://reader035.fdocuments.us/reader035/viewer/2022062417/55152dee5503465e608b5895/html5/thumbnails/9.jpg)
NTTS 2009 Brussels February 20 9
Coefficients suggested by the % of residential areaVersion 3 of the disaggregated grid
![Page 10: NTTS 2009 Brussels February 20 1 A Downscaled Population Density Map of the EU from Commune Data and Land Cover Information Javier.gallego@jrc.it NOTES.](https://reader035.fdocuments.us/reader035/viewer/2022062417/55152dee5503465e608b5895/html5/thumbnails/10.jpg)
NTTS 2009 Brussels February 20 10
Application of logit regression
• Assumption: the probability that a random point has residential land use depends on the CLC class and on the average population density of the commune
• The logit model assumes more specifically:
• Where Jc is an 0-1 indicator of the CLC class c
mii YLCfLUSp ,"Resid."
mmcc
c YbJbappplogit 1log
![Page 11: NTTS 2009 Brussels February 20 1 A Downscaled Population Density Map of the EU from Commune Data and Land Cover Information Javier.gallego@jrc.it NOTES.](https://reader035.fdocuments.us/reader035/viewer/2022062417/55152dee5503465e608b5895/html5/thumbnails/11.jpg)
NTTS 2009 Brussels February 20 11
Residuals of the logit regression (2001)
The residuals of the logit regression can be used for the geographical tuning of the coefficients(not yet done…)
![Page 12: NTTS 2009 Brussels February 20 1 A Downscaled Population Density Map of the EU from Commune Data and Land Cover Information Javier.gallego@jrc.it NOTES.](https://reader035.fdocuments.us/reader035/viewer/2022062417/55152dee5503465e608b5895/html5/thumbnails/12.jpg)
NTTS 2009 Brussels February 20 12
EM Algorithm
Iterative algorithm (Expectation – Maximum likelihood): • Assumption: the population Xmc in land cover class c for the commune m
follows a Poisson distribution with parameter Uc x Scm • M step computes a maximum lilelihood estimator of Uc
• E step makes an adjustment to ensure that the population attributed to the commune’s territory equals Xm (known)
![Page 13: NTTS 2009 Brussels February 20 1 A Downscaled Population Density Map of the EU from Commune Data and Land Cover Information Javier.gallego@jrc.it NOTES.](https://reader035.fdocuments.us/reader035/viewer/2022062417/55152dee5503465e608b5895/html5/thumbnails/13.jpg)
NTTS 2009 Brussels February 20 13
Validation in 5 countries
• A reliable reference grid available for 5 countries with 1 km2 cells• To be extended to other countries• Disagreement index for map m:
jrefjmjm YY ,,
cell Disaggregated map
Reference map
disagreement of different disaggregated maps with reference data
Austria
Denmark Finland Sweden
Netherlands
Communes (non disaggregated) 8.96 6.08 6.79 12.48 18.3
CLC-iterative 4.55 4.07 5.44 8.05 7.13
CLC-LUCAS simple 4.39 3.97 5.06 8.09 9.03
CLC-LUCAS logit 4.35 3.95 5.03 8.07 7.08
CLC EM 4.50 3.98 5.12 8.08 9.29
CLC limiting variable 4.83 4.02 5.10 7.78 7.95
![Page 14: NTTS 2009 Brussels February 20 1 A Downscaled Population Density Map of the EU from Commune Data and Land Cover Information Javier.gallego@jrc.it NOTES.](https://reader035.fdocuments.us/reader035/viewer/2022062417/55152dee5503465e608b5895/html5/thumbnails/14.jpg)
NTTS 2009 Brussels February 20 14
Some conclusions
• Disaggregated population density maps with the help of CORINE Land Cover reduces the disagreement with a reference map– Improvement between 20% and 60% – But still far from perfect
• The logit model seems to give the best results among the approaches tested, but the differences are very small (except for NL)
• In communes that contain large urban and non-urban areas, all the disaggregated maps tested seem to over-estimate the density in non-urban areas.
![Page 15: NTTS 2009 Brussels February 20 1 A Downscaled Population Density Map of the EU from Commune Data and Land Cover Information Javier.gallego@jrc.it NOTES.](https://reader035.fdocuments.us/reader035/viewer/2022062417/55152dee5503465e608b5895/html5/thumbnails/15.jpg)
NTTS 2009 Brussels February 20 15
Further developments
• Reference maps available might be used also for calibrating models, not only for validation– Downscaling the reference maps to 1 ha resolution?
• New layers of geographic data should be tried, e.g.: – night time light– Tele-Atlas
• Adding Switzerland and Norway• Producing a first version with 2006 data
– Still some countries missing for population data– CLC2006 not yet distributed
• Layer of population density changes• Introducing more detailed data for urban areas (Urban Atlas)