MERIT DEM

The MERIT DEM, or Multi-Error-Removed Improved-Terrain DEM, was developed by removing multiple error components such as absolute bias, stripe noise, speckle noise, and tree height bias from existing spaceborne Digital Elevation Models (DEMs) like SRTM3 v2.1 and AW3D-30m v1. This global dataset represents terrain elevations at a 3-arcsecond resolution (approximately 90m at the equator) and covers land areas between 90N and 60S, referenced to the EGM96 geoid. A hydrologically adjusted version is also available as part of the MERIT Hydro datasets.

This high-accuracy global DEM was created by eliminating major error components from existing DEMs, including NASA SRTM3, JAXA AW3D, and Viewfinder Panoramas' DEM. The development involved separating absolute bias, stripe noise, speckle noise, and tree height bias using multiple satellite datasets and advanced filtering techniques. After error removal, the proportion of land areas mapped with 2m or better vertical accuracy increased significantly from 39% to 58%. Notable improvements were observed in flat regions where height errors previously exceeded topography variability, leading to clearer representations of landscapes such as river networks and hill-valley structures.

The MERIT DEM provides elevation data in meters, referenced to WGS84 and EGM96. The data is organized into 5-degree x 5-degree tiles (6000 pixels x 6000 pixels), with filenames indicating the lower-left pixel's center. These tiles are further compressed into 30-degree by 30-degree packages. The data format is 'Fortran Direct Access Format' (equivalent to ESRI 'FLT' raster with an HDR file, or GrADS binary with a CTL file), stored as 4-byte float, little endian, and is also available in GeoTiff format.