CoastalDEM90® is a 3 arcsecond (~90 meter) horizontal resolution digital elevation model based on SRTM 3.0, a near-global dataset derived from satellite radar during a NASA mission in 2000. SRTM is known to contain significant error caused by factors such as topology, vegetation, buildings, and random noise. We have used machine learning techniques to estimate SRTM elevation error in coastal areas between (and including) 120m in nominal SRTM elevation. Each pixel in a CoastalDEM raster within the relevant elevation and spatial domains represents the corrected elevation at that point - the result of subtracting estimated error from SRTM 3.0. Pixels outside these domains are set to their original SRTM value. The Coastal DEM dataset was supplied to Worldpop under license for non-commercial use. It was modified to replace the value -32767 with those values from a SRTM-based elevation model that WorldPop have (https://hub.worldpop.org/geodata/listing?id=58) Bias (m) RMSE (m) LE90 (m) LE95 (m) USA (Original SRTM) 3.67 5.36 9.12 11.23 USA (Corrected) < 0.11 2.39 3.90 4.99 Australia (Original) 2.49 4.15 6.76 8.98 Australia (Corrected) - 0.11 2.46 3.94 5.16

CoastalDEM90® is a 3 arcsecond (~90 meter) horizontal resolution digital elevation model based on SRTM 3.0, a near-global dataset derived from satellite radar during a NASA mission in 2000. SRTM is known to contain significant error caused by factors such as topology, vegetation, buildings, and random noise. We have used machine learning techniques to estimate SRTM elevation error in coastal areas between (and including) 120m in nominal SRTM elevation. Each pixel in a CoastalDEM raster within the relevant elevation and spatial domains represents the corrected elevation at that point - the result of subtracting estimated error from SRTM 3.0. Pixels outside these domains are set to their original SRTM value. The Coastal DEM dataset was supplied to Worldpop under license for non-commercial use. It was modified to replace the value -32767 with those values from a SRTM-based elevation model that WorldPop have (https://hub.worldpop.org/geodata/listing?id=58) Bias (m) RMSE (m) LE90 (m) LE95 (m) USA (Original SRTM) 3.67 5.36 9.12 11.23 USA (Corrected) < 0.11 2.39 3.90 4.99 Australia (Original) 2.49 4.15 6.76 8.98 Australia (Corrected) - 0.11 2.46 3.94 5.16