combining satellite imagery and machine learning to ......high-level overview transfer learning...
TRANSCRIPT
Mo#va#on
CombiningSatelliteImageryandMachineLearningtoPredictPoverty
NealJean,MichaelXie,StefanoErmon{nealjean,sxie,ermon}@stanford.edu
References[1]C.Elvidge,K.Baugh,etal.ProceedingsoftheAsia-PacificAdvancedNetwork,2013.[2]J.Blumenstock,G.Cadamuro,andR.On,Science350,6264(2015).[3]M.Xie,N.Jean,etal.CoRR1510.00098(2015),hXp://arxiv.org/abs/1510.00098.
High-leveloverview
Transferlearningapproach Results§ Globalpovertyline:$1.90/person/day
§ Almost1billionpeopleliveinabjectpoverty
§ Lackofreliabledataindevelopingcountriesposesamajorchallengeformakinginformedpolicydecisions
§ Goal:Accuratelyandscalablypredictpovertyandwealthmeasuresfromday#mesatelliteimages,usingonlypubliclyavailabledata
X1 X2 X3 X4 Xn
Convolu<onalNeuralNetwork
Y1 Y2 Y3 Y4 Yn
Predic<ons:Economicindicators
Inputs:Day#mesatelliteimagery
Low-dimensionalfeaturerepresenta<on
§ Standardsupervisedlearningwon’twork—thereisn’tenoughgroundtruthpovertydata
§ Keyidea:Usenighgmelightintensityasaproxyforeconomicdevelopment
§ Trainaconvolu#onalneuralnetwork(CNN)toextractimagefeaturesrelevanttonighgmelights
§ Asubsetofthesefeaturesarealsousefulforpredic#ngeconomicwell-being
NorthKoreavs.SouthKorea
Learnedfeaturescorrespondingtobuildings,undevelopedareas,water,androads
−2 −1 0 1 2 3
−1
0
1
2
pred
icte
d as
set s
core
observed asset score
Nigeria, 2013r2 = 0.68
−1 0 1 2 3 4
0
1
2
pred
icte
d as
set s
core
observed asset score
Tanzania, 2010r2 = 0.57
−2 −1 0 1 2 3
−1
0
1
pred
icte
d as
set s
core
observed asset score
Uganda, 2011r2 = 0.69
−1 0 1 2 3 4 5
−1
0
1
2
3
pred
icte
d as
set s
core
observed asset score
Malawi, 2010r2 = 0.55
−1 0 1 2 3 4 5
0
1
2
pred
icte
d as
set s
core
observed asset score
Rwanda, 2010r2 = 0.75
a b
c d
e
§ Task:Predictconsump#onexpendituresandassetwealthin5Africancountries
Asset-basedwealthpredic#onsfor(a)Nigeriaand(b)Tanzania
Nigeria Tanzania Uganda Malawi Pooled
Co
un
try E
valu
ate
d O
n
Nigeria
Tanzania
Uganda
Malaw
iPooled
Consumption Expenditures
Country Trained On
Nigeria Tanzania Uganda Malawi Rwanda Pooled
Nigeria
Tanzania
Uganda
Malaw
iRwanda
Pooled
Co
un
try E
valu
ate
d O
n
Assets
Country Trained On
0.69 0.50 0.46 0.24 0.39 0.63
0.43 0.58 0.51 0.40 0.47 0.54
0.56 0.61 0.66 0.55 0.56 0.62
0.40 0.42 0.43 0.55 0.42 0.46
0.55 0.68 0.66 0.59 0.75 0.71
0.50 0.45 0.46 0.41 0.43 0.56
0.5
0.75
1
0.25
0
r2
0.41 0.30 0.26 0.19 0.39
0.44 0.56 0.47 0.48 0.52
0.34 0.38 0.46 0.37 0.44
0.25 0.34 0.37 0.42 0.36
0.42 0.40 0.41 0.33 0.45
a b
§ AccuracycomparesfavorablywithrecentstudyinSciencethatusesmobilephonedatatopredictpoverty
§ Modelsgeneralizewellacrossborders,sugges#ngthatsatelliteimageryrevealssharedfeaturesofpoverty
Cross-bordergeneraliza#onfor(a)expenditureand(b)assetmodels