What is NASADEM and when it will be released?

Question

I heard some time ago about a new global DEM called NASADEM that was going to be released in 2017, and promised to be the best global DEM to date. What exactly is NASADEM and when will it be available?

Answer 1

NASADEM is a full reprocessing of the SRTM data using state-of-the-art interferometric processing techniques. It also improves accuracy, reduce gaps and improve the quality of the data used to fill gaps (using GDEM v3). More details are described here.

The final version is not ready yet, but a provisional version has been released (not officially) and can be downloaded here: https://e4ftl01.cr.usgs.gov/provisional/MEaSUREs/NASADEM/

In your area of interest look for the "hgt_srtmOnly_R4" folder for the SRTM only data (i.e., not void filled) and in the "hgt_merge_I2" folder for the void filled data. Note that the former contains ellipsoidal elevations and the later geoidal ones.

This provisional NASADEM does have clear improvements over SRTM v3, but I would still recommend to wait for the final version, as there are still many issues. GDEM v3 dataset has not been released yet to the public, but it is already available to NASA, as stated here. By looking at the data, it is clear to me that it was indeed used in the void-filled version of this provisional dataset.

The tiles downloaded from that server above don't have all the ancillary/header information to be loaded in most GIS software, but David Shean wrote some scripts both for bulk download and to generate the header files, those are available in github: https://github.com/dshean/nasadem

Answer 2

NASADEM, a full reprocessing of the SRTM data (Merged DEM Global 1 arc second) has now been released (as of 13 Feb 2020):

Press release:

https://lpdaac.usgs.gov/news/release-nasadem-data-products/

Tool to import the new NASADEM into GRASS GIS, selectable by bounding box:

https://grass.osgeo.org/grass7/manuals/addons/r.in.nasadem.html

Answer 3

This link contains our analysis of NASADEM vs SRTM across North America. We used 280 million extremely accurate ICESat-2 terrain height benchmarks for the comparison. The analysis also includes AW3D30, ASTER DEMs and other DEMs for good measure.

NASA also publishes an ellipsoidal height dataset which improves accuracy a wee bit, which can be helpful if you're using bicubic interpolation. It has voids which are easy to correct. Note: its heights are not relative to sea level, and are different than what Google Earth and most other mapping products provide.

In short, NASADEM is a little better than SRTM in forests (less bias), short vegetation, wetland and urban areas, and a bit worse in barren areas and open water. Also take a look at AW3D30 v3.1.