Libya 4
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The Libya 4 site is one of the most often-used Pseudo-invariant Calibration Sites (PICS) by the Committee on Earth Observation Satellites (CEOS) Working Group for Calibration and Validation (WGCV) Infrared and Visible Optical Sensors (IVOS) and other Earth Observing communities because of its high radiometric stability and size. This site was considered by Centre National d'Etudes Spatiales (CNES) to be one of the best, based on long-term trending of North African and Arabian sites. This bright desert site is located in the Great Sand Sea and is made of sand dunes with no vegetation. Though the presence of sand dunes at the Libya 4 test site does not satisfy the criterion of flat terrain, this site exhibits reasonable spatial, spectral, and temporal uniformity and has minimal cloud cover. Aerosol loading is also usually low in the region. These characteristics make Libya 4 an ideal candidate for stability monitoring of optical sensors.
Libya 4 has been frequently used for various optical sensor calibration stability monitoring, cross-calibration, inter-comparison, and absolute calibration [1, 2, 3, 4, 5]. This site has been used for low-, medium-, and high-resolution sensor calibration over time by satellites/sensors such as Landsat, Moderate Resolution Imaging Spectroradiometer (MODIS), Satellite pour l’Observation de la Terre (SPOT), Visible Infrared Imaging Radiometer Suite (VIIRS), and Advanced very high-resolution radiometer (AVHRR). The spatial and temporal stability (within a 3% threshold) of this site makes it very useful to the Earth Observation community. A recent study also verified the stability of this site using a sensor data harmonization technique [6].
Closest AERONET station: El_Farafra [ 27.06, 27.99], 482.4 km
| Location (City, State, Country): |
Libya, Africa
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|---|---|
| Landsat WRS - 2 Path / Row: |
181/40
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| Center Latitude (degrees): |
N 28.55
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| Center Longitude (degrees): |
E 23.39
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| CEOS Region of Interest |
N 29.05, E 22.89 Search this area in EarthExplorer (Landsat 8-9 Collection 2 Level-1) - date range, datasets, cloud cover and other criteria can be modified once initial results are returned |
| CNES Region of Interest |
N 28.65, E 23.29 Search this area in EarthExplorer (Landsat 8-9 Collection 2 Level-1) - date range, datasets, cloud cover and other criteria can be modified once initial results are returned |
| Size of Usable Area (km): |
75 x 75
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| UTM Zone: |
34
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| Altitude above sea level (meters): |
118
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| Purpose: |
Radiometry
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| Status: |
Active
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- Bhatt, R.; Doelling, D.R.; Wu, A.; Xiong, X.; Scarino, B.R.; Haney, C.O.; Gopalan, A. Initial stability assessment of S-NPP VIIRS reflective solar band calibration using invariant desert and deep convective cloud targets. Remote Sens. 2014, 6, 2809–2826.
- Yamamoto, H.; Kamei, A.; Nakamura, R.; Tsuchida, S. Long-term cross-calibration of the Terra ASTER and MODIS over the CEOS calibration sites. In Proceedings of the Earth Observing Systems XVI, San Diego, CA, USA, 13 September 2011.
- Mishra, N.; Helder, D.; Angal, A.; Choi, J.; Xiong, X. Absolute calibration of optical satellite sensors using Libya 4 pseudo invariant calibration site. Remote Sens. 2014, 6, 1327–1346.
- Chander, Gyanesh, Xiaoxiong Jack Xiong, Taeyoung Jason Choi, and Amit Angal. "Monitoring on-orbit calibration stability of the Terra MODIS and Landsat 7 ETM+ sensors using pseudo-invariant test sites." Remote Sensing of Environment 114, no. 4 (2010): 925-939.
- Barsi, Julia A., Bahjat Alhammoud, Jeffrey Czapla-Myers, Ferran Gascon, Md Obaidul Haque, Morakot Kaewmanee, Larry Leigh, and Brian L. Markham. "Sentinel-2A MSI and Landsat-8 OLI radiometric cross comparison over desert sites." European Journal of Remote Sensing 51, no. 1 (2018): 822-837.
- Tuli, F.T.Z.; Pinto, C.T.; Angal, A.; Xiong, X.; Helder, D. New Approach for Temporal Stability Evaluation of Pseudo-Invariant Calibration Sites (PICS). Remote Sens. 2019, 11, 1502.
Note: This information has been compiled by the USGS ECCOE Team, using the best sources currently known. Updates will be made as more information becomes available. Please contact eccoe@usgs.gov with any updates you would like to contribute.