A technical overview of how population totals are computed and disaggregated in PopEx.
Overview
Population Explorer aggregates global gridded datasets to compute total population inside any drawn or selected boundary. Behind the simple “total” figure are algorithms that reconcile global raster sources (LandScan, WorldPop) with administrative age/sex breakdowns (ASB) to produce meaningful, comparable results.
Algorithms for Totals
Input data: LandScan (ambient, ~1 km), WorldPop (residential, ~100 m), normalized to census totals.
Aggregation: Polygon overlay sums grid cells, partial overlaps weighted by geodesic area.
Consistency checks: Totals checked against control surfaces; deviations recalibrated.
Folder-level totals: Aggregated recursively from polygon-level results.
Age/Sex Breakdown (ASB) Algorithm
Step 1: Census ratios imported by admin unit.
Step 2: Ratios blended across raster cells.
Step 3: Cross-boundary polygons weighted by overlap.
Step 4: Output in 5-year age bands × sex categories.
LandScan vs WorldPop
LandScan: Ambient totals; ASB applied post-allocation at ~1 km.
WorldPop: Residential totals; finer ~100 m disaggregation.
Key difference: LandScan smooths more; WorldPop captures intra-urban variation.
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