The latest release of the GEBCO 30 arc-second global grid of elevations, GEBCO_2014 Grid, was published in 2014. It provides an update to the previous release, GEBCO_08 Grid.
It was largely generated by combining quality-controlled ship depth soundings with interpolation between sounding points guided by satellite-derived gravity data. Where they improve on the existing grid, data sets developed by other methods are included to create a continuous terrain model for ocean and land.
https://www.gebco.net/data_and_products/gridded_bathymetry_data/
The Japan Aerospace Exploration Agency (JAXA) released "ALOS World 3D – 30m (AW3D30)", the global digital surface model (DSM) dataset with a horizontal resolution of approx. 30-meter mesh (1×1 arcsecond), free of charge in May 2015.
https://www.eorc.jaxa.jp/ALOS/en/aw3d30/
The SRTM digital elevation data provided on this site has been processed to fill data voids and to facilitate its ease of use by a wide group of potential users. This data is provided in an effort to promote the use of geospatial science and applications for sustainable development and resource conservation in the developing world. Digital elevation models (DEM) for the entire globe, covering all of the countries of the world, are available for download on this site.
https://cgiarcsi.community/data/srtm-90m-digital-elevation-database-v4-1/
The EarthExplorer (EE) user interface is an online search, discovery, and ordering tool developed by the United States Geological Survey (USGS). EE supports the searching of satellite, aircraft, and other remote sensing inventories through interactive and textual-based query capabilities. Registered users of EE have access to more features than guest users.
https://earthexplorer.usgs.gov/
https://earthexplorer.usgs.gov/bulk/
https://wiki.earthdata.nasa.gov/display/EL/How+To+Access+Data+With+cURL+And+Wget
The National Elevation Dataset (NED) is a raster product assembled by the U.S. Geological Survey. NED is designed to provide National elevation data in a seamless form with consistent datums, elevation unit, and coordinate reference system. The NED assembly process involves edge matching and mosaicking elevation data into NED layers.
Seamless NED layers are available at the following resolutions:
- one third arc-second (approximately 10 meters) resolution for the conterminous United States and portions of Alaska,
- one arc-second (approximately 30 meters) for the conterminous United States, Hawaii, Puerto Rico, U.S. territorial islands, Mexico, and Canada,
- and a resolution of two arc-second (approximately 60 meters) resolution is available for all of Alaska.
In addition to seamless elevation layers, NED is also available at a one ninth arc-second (approximately 3 meters) resolution. The NED one ninth arc-second layer is not seamless. At this time the one ninth arc-second NED layer does covers only a portion the United States.
No blending, edge matching or mosaicking is performed between projects.
https://www.usgs.gov/core-science-systems/ngp/3dep/about-3dep-products-services
ftp://rockyftp.cr.usgs.gov/vdelivery/Datasets/Staged/NED/1/
ftp://rockyftp.cr.usgs.gov/vdelivery/Datasets/Staged/NED/13/
ftp://rockyftp.cr.usgs.gov/vdelivery/Datasets/Staged/NED/19/