Posted on: 11/01/2019 - Updated on: 2/27/2020

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CoastalDEM® is a digital terrain model providing bare earth elevations for low-lying coastal areas between latitudes 60N and 56S. It has continuous vertical resolution and 1 arc second (~100 foot) horizontal resolution. By contrast, NASA's SRTM DEM provides elevation in 1-meter (3.3-ft) vertical increments instead of continuous values. Because SRTM is a digital surface model that fails to exclude treetops and rooftops, SRTM overestimates ground elevations by more than 2 meters (6 feet) on average and, in dense cities, more than twice that. As a result, SRTM severely underestimates coastal threats. SRTM’s average error exceeds the height of most coastal floods today and most 21st century sea level rise projections – meaning that many areas face much greater flood risk than SRTM-based analyses suggest.  Assessments based on CoastalDEM find more than 3X the number of people on land potentially exposed to these coastal threats, compared to SRTM.

Climate Central scientists created CoastalDEM using sophisticated machine-learning techniques to improve on the SRTM dataset. Validation tests indicate CoastalDEM has almost no vertical bias (under four inches in the most reliable tests) and cuts SRTM's error scatter nearly in half.

CoastalDEM also outperforms other recent global DEMs: AW3D30 and MERITDEM produce coastal exposure estimates similar to SRTM.

CoastalDEM is based on rigorous peer-reviewed science – and costs pennies on the dollar versus commercial products that may have vertical accuracy comparable to CoastalDEM.

View the CoastalDEM flier to see sample images and comparison statistics.


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Climate Central is an independent nonprofit organization that was founded in 2008 to meet the need for a central authoritative source for climate change information.

Climate Central scientists publish peer-reviewed research on climate science; energy; impacts such as sea level rise; climate attribution and more. But our work isn't confined to scientific journals. We investigate and synthesize weather and climate data and science to equip local communities and media with the tools they need to visualize the threat of climate change and the need for practical solutions.


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