The Global Fiducials Library (GFL) is a long-term archive of images from U.S. National Imagery Systems which represents a long-term periodic record for selected scientifically important sites. The GFL was created to be the collection, archive and data management component of the Global Fiducials Program.

The Global Fiducials Program is a collaborative effort between Federal Civil Agencies, Academia, and the Intelligence Community. The principal goal of the Global Fiducials Program was to build and maintain a long-term record of data to support scientists and policy makers involved in that collaborative effort. At the inception of the Program, it was hoped that at some point - perhaps as much as twenty-five years into the future - the acquired data could be openly released to support future scientists and policy makers as well. Since the 1990s, the Global Fiducials Program has been periodically collecting images of environmentally significant sites around the world.

The GFL, which is the archive that maintains this long-term imagery record, is managed by the U.S. Geological Survey under the National Civil Applications Program, in partnership with the Civil Applications Committee

North American ecosystems are critical components of the global carbon cycle, exchanging large amounts of carbon dioxide and other gases with the atmosphere. Net ecosystem exchange (NEE) quantifies these carbon fluxes, but current continental-scale estimates contain high levels of uncertainty. Root-zone soil moisture (RZSM) and its spatial and temporal hetergeneity influence NEE and contribute as much as 60-80 percent to the uncertainty. Energy and CO2 Fluxes have been monitored from 1997 to 2007 using Bowen Ratio technique, and since spring of 2004 with eddy covariance.

Gemini photography was acquired between March 23, 1965 and November 15, 1966. The images were collected as part of the Synoptic Terrain Photography and the Synoptic Weather Photography experiments during Gemini Missions III through XII. Hand-held cameras were used to obtain photographs of geologic, oceanic, and meteorologic targets. The Gemini archive consists primarily of 70-mm black and white (B/W), color, and color-infrared (CIR) film. All Gemini photographs are distributed by the USGS Earth Resources Observation and Science (EROS) Center as digital products only.

Skylab photography was acquired between May 22, 1973 and February 8, 1974 during three manned flights. The Skylab Earth Resources Experiment Package used two photographic remote sensing systems. The Multispectral Photographic Camera (S190A), was a six-camera array, in which each camera used 70-mm film and a six-inch focal length lens. The acquired film ranges from narrow-band B/W to broad-band color and CIR. The Earth Terrain Camera (S190B) consisted of a single high-resolution camera which used five-inch film and an 18-inch focal length lens. The acquired film includes B/W, black and white infrared (BIR), color, and CIR. All Skylab photographs are distributed by the USGS EDC as digital products only.

Shuttle Large Format Camera (LFC) images were acquired from the Space Shuttle Challenger Mission on October 5-13, 1984. The LFC was mounted in the cargo bay, and was operated via signals from ground controllers. The archived imagery includes 9 x 18 inch B/W, natural color, and CIR film. Shuttle LFC photographs are distributed by the USGS EDC as digital products only.

Spaceborne Imaging Radar-C (SIR-C) is part of an imaging radar system that was flown on board two Space Shuttle flights (9 - 20 April, 1994 and 30 September - 11 October, 1994). The USGS distributes the C-band (5.8 cm) and L-band (23.5 cm) data. All X-band (3 cm) data is distributed by DLR.

There are several types of products that are derived from the SIR-C data:

Survey Data is intended as a "quick look" browse for viewing the areas that were imaged by the SIR-C system. The data consists of a strip image of an entire data swath. Resolution is approximately 100 meters, processed to a 50-meter pixel spacing. Files are distributed via File Transfer Protocol (FTP) download.

Precision (Standard) Data consists of a frame image of a data segment, which represents a processed subset of the data swath. It contains high-resolution multifrequency and multipolarization data. All precision data is in CEOS format.

The following types of precision data products are available:

Single-Look Complex (SLC) consists of one single-look file for each scene, per frequency. Each data segment will cover 50 kilometers along the flight track, and is broken into four processing runs (two L band, two C-band). Resolution and polarization will depend on the mode in which the data was collected. Available as calibrated or uncalibrated data.

Multi-Look Complex (MLC) is based on an averaging of multiple looks, and consists of one file for each scene per frequency. Each data segment will cover 100 km along the flight track, and is broken into two processing runs (one L band and one C band). Polarization will depend on the modes in which the looks were collected. The data is available in 12.5- or 25-meter pixel spacing.

Reformatted Signal Data (RSD) consists of the raw radar signal data only. Each data segment will cover 100 km along the flight track, and the segment will be broken into two processing runs (L-band and C-band).

Interferometry Data consists of experimental multitemporal data that covers the same area. Most data takes were collected during repeat passes within the second flight (days 7, 8, 9, and/or 10). In addition, nine data takes were collected during the second flight that were repeat passes of the first flight. Most data takes were also single polarization, although dual and quad polarization data was also collected on some passes. A Digital Elevation Model (DEM) is not included with any of the SIR-C interferometric data.

The following types of interferometry products are available:

Interferometric Single-Look Complex (iSLC) consists of two or more uncalibrated SLC images that have been processed with the same Doppler centroid to allow interferometric processing. Each frame image covers 50 kilometers along the flight track. The data is available in CEOS format.

Raw Interferogram product (RIn) involves the combination of two data takes over the same area to produce an interferogram for each frequency (L-band and C-band). The data is available in TAR format.

Reformatted Signal Data (RSD) consists of radar signal data that has been processed from two or more data takes over the same area, but the data has not been combined. Although this is not technically an interferometric product, the RSD can then be used to generate an interferogram. Each frame will cover 100 km along the flight track. The data is available in CEOS format.

NASA has released version 2 of the Shuttle Radar Topography Mission digital
topographic data (also known as the "finished" version). Version 2 is the
result of a substantial editing effort by the National Geospatial Intelligence
Agency and exhibits well-defined water bodies and coastlines and the absence of
spikes and wells (single pixel errors), although some areas of missing data
('voids') are still present. The Version 2 directory also contains the vector
coastline mask derived by NGA during the editing, called the SRTM Water Body
Data (SWBD), in ESRI Shapefile format.

[Summary provided by NASA.]

Sentinel-1B Single-pol ground projected high and full resolution metadata

Sentinel-1B slant-range product

Sentinel-1A Single-pol ground range detected full resolution images

Metadata for Sentinel-1A level zero product

RADARSAT-1 Level 1 Amplitude Images