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Full catalog/SRTMGL3N
SRTMGL3N·v003·dataset

Count of source scenes per pixel (SRTM, 90 m)

NASA Shuttle Radar Topography Mission Global 3 arc second number V003
land NASA LPCLOUD Level 3 Binary
In plain English

What it measures. Not elevation itself, but a bookkeeping count of how many source radar scenes went into each pixel of the 90-meter global elevation map.

How it's made. A companion file to NASA's Shuttle Radar Topography Mission elevation data, gathered during the 11-day STS-99 Space Shuttle Endeavour flight in 2000 that radar-mapped most of Earth's land.

How & where you'd use it. A quality and provenance helper for the elevation data. It tells specialists how much raw coverage backs each spot, and is used alongside the main elevation files rather than on its own.

What's measured

SPECTRAL/ENGINEERING › RADAR › RADAR IMAGERYLAND SURFACE › TOPOGRAPHY › TERRAIN ELEVATIONLAND SURFACE › TOPOGRAPHY › TERRAIN ELEVATION › TOPOGRAPHICAL RELIEF MAPS

Coverage & cadence

  • Time span2000-02-11 → 2000-02-21
  • Measured bySTS-99 (SRTM)
  • Processing levelLevel 3
  • Spatial extent-180, -56, 180, 60
  • FormatsBinary
  • StatusCOMPLETE

What you can do with it

  • Track deforestation, fire scars and land-cover change
  • Monitor crop and vegetation health (NDVI/EVI)
  • Map how built-up vs. green an area is over time
Official description

The Land Processes Distributed Active Archive Center (LP DAAC) is responsible for the archive and distribution of NASA Making Earth System Data Records for Use in Research Environments ([MEaSUREs](https://earthdata.nasa.gov/about/competitive-programs/measures )) SRTM, which includes the global 3 arc second (~90 meter) number product. The NASA SRTM data sets result from a collaborative effort by the National Aeronautics and Space Administration (NASA) and the National Geospatial-Intelligence Agency (NGA - previously known as the National Imagery and Mapping Agency, or NIMA), as well as the participation of the German and Italian space agencies. This collaboration aims to generate a near-global digital elevation model (DEM) of Earth using radar interferometry. SRTM was the primary (and virtually only) payload on the STS-99 mission of the Space Shuttle Endeavour, which launched February 11, 2000 and flew for 11 days. The SRTM swaths extended from ~30 degrees off-nadir to ~58 degrees off-nadir from an altitude of 233 kilometers (km), creating swaths ~225 km wide, and consisted of all land between 60° N and 56° S latitude to account for 80% of Earth's total landmass. Ancillary one-byte (0 to 255) "NUM" (number) files were produced for NASA SRTM Version 3. These files have names corresponding to the elevation files, except with the extension ".NUM" (such as N37W105.NUM). The elevation files use the extension ".HGT", meaning height (such as N37W105.HGT). The separate NUM file indicates the source of each DEM pixel; the number of ASTER scenes used (up to 100), if ASTER; and the number of SRTM data takes (up to 24), if SRTM. The NUM file for both 3 arc second products (whether sampled or averaged) references the 3 x 3 center pixel. Note that NUMs less than 6 are water and those greater than 10 are land. The 3 arc second data was derived from the 1 arc second using sampling and averaging methods. (See Figure 3 in the User Guide) The global 3 arc second number product is also available in NetCDF4 format as the SRTMGL3_NUMNC dataset and can be used with the corresponding SRTMGL3_NC elevation product. Known Issues * Known issues in the NASA SRTM are described in the following publication: * Rodriguez, E., C. S. Morris, and J. E. Belz (2006), A global assessment of the SRTM performance, Photogramm. Eng. Remote Sens., 72, 249–260. https://doi.org/10.14358/PERS.72.3.249

Get the data

srtmgl3n_access.py
import earthaccess
earthaccess.login(strategy="netrc")          # free Earthdata Login

results = earthaccess.search_data(
    short_name="SRTMGL3N",
    version="003",
    bounding_box=(-122.5, 37.2, -121.8, 37.9),  # your area (W,S,E,N)
    temporal=("2024-01-01", "2024-12-31"),       # your dates
)
files = earthaccess.open(results)   # stream straight from LPCLOUD
Browsing CMR needs no login. Downloading or streaming bytes needs a free Earthdata Login + the earthaccess package.