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Full catalog/SRTMGL1N
SRTMGL1N·v003·dataset

Count of data points behind the elevation map (30 m)

NASA Shuttle Radar Topography Mission Global 1 arc second number V003
land NASA LPCLOUD Level 3 Binary
In plain English

What it measures. A companion layer to the 30 meter elevation map that records, for each grid cell, how many source data points went into that elevation value. It is information about data quality, not elevation itself.

How it's made. Produced alongside the Shuttle Radar Topography Mission elevation data from the radar flown on Space Shuttle Endeavour, as a one-byte count file.

How & where you'd use it. A building-block quality layer used together with the elevation map to judge how well-supported each measurement is; specialists use it rather than the general public.

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 )) Shuttle Radar Topography Mission (SRTM), which includes the global 1 arc second (~30 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 global 1 arc second number product is also available in NetCDF4 format as the SRTMGL1_NUMNC dataset and can be used with the corresponding SRTMGL1_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

srtmgl1n_access.py
import earthaccess
earthaccess.login(strategy="netrc")          # free Earthdata Login

results = earthaccess.search_data(
    short_name="SRTMGL1N",
    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.