Skip to main content
Home

Earth Resources Observation and Science (EROS) Center

Main Menu

  • EROS Home
  • Image Gallery
  • Video Library
  • Earthshots
  • Remote Sensing Classroom

Earthshots

  • Earthshots
    • Sharq El Owainat, Egypt
      • Picking Calibration Sites
      • Watering the Sahara
      • Landsat’s Accuracy
      • Earth As Art
  • Download Cards
  • More Information
  • Contact Information
Earthshots Logo

Picking Calibration Sites A Sharq El Owainat, Egypt story

Agriculture  / 
Deserts
  1. Sharq El Owainat, Egypt
  2. Picking Calibration Sites
Description

Engineers use test sites around the world to make sure Landsat imagery is consistent and accurate. These calibration test sites are regions on the Earth that remain stable over long periods of time. They do not change year to year or season to season. They are typically deserts or dry lakebeds with very low humidity, low atmospheric changes, and little to no human intervention.

These sites are described as pseudo-invariant. They are not completely invariant because no site can be perfectly stable over time and varies to some degree. So engineers refer to the sites as Pseudo-Invariant Calibration Sites, or PICS.

The idea of studying these test sites is simple. Engineers look at a spot of land that is expected to remain consistent. The reflectance at different wavelengths of light in the Landsat data should stay stable. When changes occur in these reflectance values, it may mean the sensor’s response has shifted.

Examples of other test sites are the remote desert sands of Libya, the Railroad Valley Playa lakebed in Nevada, and even the straight bridge that crosses Lake Pontchartrain, Louisiana. (The span of the bridge happens to be nearly aligned with the Landsat ground track.)

View Related Imagery & Stories

Location

June 20, 2019, Landsat 8 (path/row 181/40) — calibration test site in Libya

June 20, 2019, Landsat 8 (path/row 181/40) — calibration test site in Libya

July 10, 2019, Landsat 8 (path/row 40/33) — calibration test site at Railroad Valley Playa, Nevada

July 10, 2019, Landsat 8 (path/row 40/33) — calibration test site at Railroad Valley Playa, Nevada

Aug. 29, 2019, Landsat 8 (path/row 22/39) — causeway over Lake Pontchartrain, Louisiana

Aug. 29, 2019, Landsat 8 (path/row 22/39) — causeway over Lake Pontchartrain, Louisiana

June 20, 2019, Landsat 8 (path/row 181/40) — calibration test site in Libya
July 10, 2019, Landsat 8 (path/row 40/33) — calibration test site at Railroad Valley Playa, Nevada
Aug. 29, 2019, Landsat 8 (path/row 22/39) — causeway over Lake Pontchartrain, Louisiana

Sharq El Owainat, Egypt Additional Imagery & Stories

Earth As Art
Earth As Art

The view of this region from Landsat is so fascinating, it’s the subject of two Earth As Art images. These and all Earth As Art images can be download...

Read More
Landsat’s Accuracy
Landsat’s Accuracy

The Sharq El Owainat airport is visible on the right side of these images. The runway appears in the 1997 image. Landsat’s accuracy is key to other sy...

Read More
Watering the Sahara
Watering the Sahara

One of the best test sites, named Egypt-2, was steadily reliable until around the late 1990s. In a vast expanse of Sahara Desert in southern Egypt, ce...

Read More
  • DOI Privacy Policy
  • Legal
  • Accessibility
  • Site Map
  • Contact USGS

  • U.S. Department of the Interior
  • DOI Inspector General
  • White House
  • E-gov
  • No Fear Act
  • FOIA