Creating Spatial Interpolation Surfaces with DHS Data [SAR11]

CREATING SPATIAL INTERPOLATION SURFACES WITH DHS DATA

DHS SPATIAL ANALYSIS REPORTS 11

SEPTEMBER 2015 This publication was produced for review by the United States Agency for International Development (USAID). The report was prepared by Peter Gething, Andy Tatem, Tom Bird, and Clara R. Burgert-Brucker of ICF International, Rockville, MD, USA.

DHS Spatial Analysis Reports No. 11

Creating Spatial Interpolation Surfaces with DHS Data

Peter Gething Andy Tatem Tom Bird Clara R. Burgert-Brucker

ICF International Rockville, Maryland, USA

September 2015

Corresponding author: Clara R. Burgert-Brucker, International Health and Development, ICF International, 530 Gaither Road, Suite 500, Rockville, MD 20850, USA; phone: +1-301-572-0446; fax: +1-301-407-6501; email: [email protected]

Acknowledgment: The authors would like to acknowledge Shireen Assaf, Mike Emch, and Mahmoud Elkasabi for their review of this report. Editor : Diane Stoy Document Production: Natalie La Roche This study was carried out with support provided by the United States Agency for International Development (USAID) through The DHS Program (#AID-OAA-C-13-00095). The views expressed are those of the authors and do not necessarily reflect the views of USAID or the United States Government. The DHS Program assists countries worldwide in the collection and use of data to monitor and evaluate population, health, and nutrition programs. For additional information about The DHS Program contact: DHS Program, ICF International, 530 Gaither Road, Suite 500, Rockville, MD 20850, USA. Phone: +1-301-407-6500; fax: +1-301-407-6501; email: [email protected]; Internet: www. dhsprogram.com.

Recommended citation: Gething, Peter, Andy Tatem, Tom Bird, and Clara R. Burgert-Brucker. 2015. Creating Spatial Interpolation Surfaces with DHS Data DHS Spatial Analysis Reports No. 11. Rockville, Maryland, USA: ICF International.

Contents Tables ......................................................................................................................................................... v Figures ........................................................................................................................................................ v Abbreviations .............................................................................................................................................. ix Preface ........................................................................................................................................................ xi Abstract ...................................................................................................................................................... xiii Executive Summary ................................................................................................................................... xv 1.

Background and Objectives ............................................................................................................ 1 1.1 Objective 1: Exploring the Potential of Bayesian Geostatistics for Interpolating DHS Survey Data ........................................................................................................................ 1 1.2 Objective 2: Exploring the Impact of DHS Cluster Displacement on the Production of Interpolated Surfaces ..................................................................................................... 2 1.3 Objective 3: Investigating the Potential for Novel Methodologies and Covariates to Address the Challenge of Mapping within Urban Areas ................................................... 3

2.

Selection of DHS Indicators and Exemplar Countries..................................................................... 5

3.

National-Level Geostatistical Mapping .......................................................................................... 7 3.1 Methods ............................................................................................................................. 7 3.1.1 Overview ............................................................................................................... 7 3.1.2 Preparation of Georeferenced DHS Indicator Data .............................................. 7 3.1.3 Exploratory Analysis .......................................................................................... 11 3.1.4 Geostatistical Modeling ...................................................................................... 13 3.2 Results .............................................................................................................................. 14 3.2.1 Access to HIV Testing in Women ...................................................................... 15 3.2.2 Stunting in Children ............................................................................................ 21 3.2.3 Anemia Prevalence in Children .......................................................................... 26 3.2.4 Access to Improved Sanitation ........................................................................... 31

4.

Effects of Cluster Centroid Displacement .................................................................................... 37 4.1 Methods ........................................................................................................................... 37 4.1.1 Overview ............................................................................................................. 37 4.1.2 Generating Displaced Data ................................................................................. 37 4.1.3 Exploration of Effect of Displacement on Statistical Properties of Data ............ 39 4.1.4 Exploration of Effect of Displacement on MBG-derived Interpolated Surfaces ............................................................................................................... 39 4.2 Results .............................................................................................................................. 40 4.2.1 Generating Displaced Data ................................................................................. 40 4.2.2 Exploration of Effect of Displacement on Statistical Properties of Data............. 44 4.2.3 Exploration of Effect of Displacement on MBG-derived Interpolated Surfaces ............................................................................................................... 46

iii

5.

The Potential of High Resolution Urban Mapping ....................................................................... 59 5.1 Methods ........................................................................................................................... 59 5.1.1 Urban Subsets of the Data and Urban Definitions .............................................. 59 5.1.2 High Resolution Urban Covariates ..................................................................... 59 5.1.3 Effects of Displacement on Linear Models in Urban Areas ............................... 60 5.1.4 Exploration of Different Approaches to Modeling Urban Settings at High Resolutions ......................................................................................................... 61 5.1.5 Kano Urban Dataset ............................................................................................ 61 5.2 Results .............................................................................................................................. 64 5.2.1 Urban Definitions ............................................................................................... 64 5.2.2 Effects of Displacement on Model Estimates ..................................................... 66 5.3 Exploration of Model Approaches to High-Resolution Datasets ..................................... 73 5.3.1 Comparison of Generalized Additive Models (GAM), Boosted Regression Trees (BRT) and Linear Models (LM) for Predicting Proportion of Children under 5 Years Old ............................................................................................... 73 5.3.2 Effects of Displacement on Models at Differing Resolutions ............................ 75

6.

Discussion ..................................................................................................................................... 77 6.1 National-level Geostatistical Mapping ............................................................................ 77 6.2 Effects of Cluster Centroid Displacement ....................................................................... 78 6.3 The Potential of High Resolution Urban Mapping .......................................................... 78 6.4 Next Steps ........................................................................................................................ 79 6.4.1 Further Improvements to the Methodology ........................................................ 79 6.4.2 Development of Use-cases for Predictive Maps ................................................. 81

7.

Conclusion ..................................................................................................................................... 83

References ................................................................................................................................................... 85

iv

Tables Table 1. Table 2.

Details of geospatial covariates assembled for use in mapping ........................................................ 9 Summary output from the covariate selection procedure for the indicator on proportion of women accessing HIV testing in the 12 months preceding the survey ........................................ 17 Table 3. Summary validation results from the model-based geostatistical map for the indicator on proportion of women accessing HIV testing in the 12 months preceding the survey ................. 17 Table 4. Summary output from the covariate selection procedure for the indicator on proportion of children