What are Landsat 7 SLC-off Gap Mask files?

Band-specific gap mask files are included with every Landsat 7 Scan Line Corrector (SLC)-off Level-1 data product. These ancillary data identify the location of all pixels affected by the original data gaps in the primary SLC-off scene.

The gap mask is provided as a series of individual band files, in compressed (GZIP) GeoTIFF format.

SLC-Off showing showing satellite image with parallel bands of missing image; and SLC-On gap mask with correlating blue bands.

Left: Sample SLC-Off image; Right: SLC gap mask

(Public domain.)

Gap Mask Legend Values:

  • green = primary scene
  • blue = fill scene 1
  • yellow = fill scene 2
  • pink = fill scene 3
  • red = no data (not filled)

For a standard SLC-off product, the data values contained within the gap mask file are:

  • Value of 0 - No data (data were missing in the original SLC-off scene)
  • Value of 1 - Populated data (data were present in the original SLC-off scene)

Learn more: Landsat 7 web page

Related Content

Filter Total Items: 7

What are the _VER.jpg and _VER.txt files that are included with the Landsat MSS and TM data?

The Verify Image (_VER.jpg) and Geometric Verify Report (_VER.txt) files are included with Landsat MSS and TM Collection 1 Level-1 scenes that have processed into Tier 1. The Verify Image File displays a colored grid of verification points to represent the accuracy of geometric correction, using cross-correlation techniques to compare the product...

Why do Landsat 7 Level-1 products contain two thermal bands?

Landsat 7 acquires thermal data in two bands from one detector in both high (Band 6H) and low (Band 6L) gain. The difference in gain settings is important to different types of studies (i.e., clouds vs. deserts). Aside from the resolution differences and saturation on the high and low ends, the two bands provide the same Digital Numbers (DN) for...

What Landsat data products are available?

There are several Landsat data products that are useful for science applications and land use/land change studies: Landsat Collections Level 1 - Ensures that the data in the Landsat Level-1 archive are consistent in processing and data quality to support time-series analyses and data stacking. Each Level-1 data product includes individual spectral...

Does the Landsat 7 Scan Line Corrector (SLC)-off artifact affect Landsat Collections tier designation?

The Landsat 7 SLC-off artifact does not change how the data are placed into Landsat Collection tiers, as tier classifications are determined by the radiometric and geometric accuracy of each scene. Learn more: Landsat Collections Landsat Data Access

What is Landsat 7 ETM+ SLC-off data?

Landsat 7 ETM+ SLC-off data refers to all Landsat 7 images collected after May 31, 2003, when the Scan Line Corrector (SLC) failed. These products have data gaps, but are still useful and maintain the same radiometric and geometric corrections as data collected prior to the SLC failure. See the Landsat 7 website for information about the SLC-off...

What are some known issues that users might find in Landsat data?

A number of artifacts and anomalies can happen to any remote sensing data. Banding, dropped scan lines, and detector failures are only a few of the anomalies that can be seen in Landsat data. Go to Landsat Known Issues for details about anomalies that have been discovered and investigated.

What are the best Landsat spectral bands for use in my research?

The Spectral Characteristics Viewer is an interactive tool that can be used to visualize how the bands--or channels--of different satellite sensors measure the intensity of the many wavelengths (colors) of light. This is also known as the relative spectral response (RSR). By overlaying the spectral curves from different features (spectra), one can...
Filter Total Items: 3
Date published: April 17, 2018

Free, Open Landsat Data Unleashed the Power of Remote Sensing a Decade Ago

In the old days, before 2008, a view of planet Earth from space often came at a cost.

Date published: December 15, 2004

USGS Offers New Landsat 7 Gap-Filled Product

The U.S. Geological Survey (USGS) has completed development of a major new product enhancement for Landsat 7 Enhanced Thematic Mapper Plus (ETM+) data captured after the Scan Line Corrector (SLC) anomaly in May of 2003. 

Date published: September 7, 1999


After soaring to space last spring, NASA’s latest Earth-imaging satellite has completed its checkout phase and is now "open for business." New images from the Landsat 7 spacecraft are now available for viewing and purchase by scientific researchers and the general public via the Internet from the United States Geological Survey (USGS) and NASA.

Filter Total Items: 10
June 30, 2018

Daily Operations of Landsat 7

What it takes each day to keep Landsat 7 operating smoothly. Hear the stories from inside the L7 Mission Operation Center.

March 13, 2008

What is Landsat 7?

Listen to hear the answer.

Illustration of the Landsat 7 Scan Line Corrector (SLC) Failure
January 30, 2008

Illustration of the Landsat 7 Scan Line Corrector (SLC) Failure

Illustration of the Landsat 7 Scan Line Corrector (SLC) Failure.

Earth As art image Bolivian Deforestation
August 1, 2000

Bolivian Deforestation

Once a vast carpet of healthy vegetation, the Amazon rain forest is changing rapidly. This image of Bolivia shows dramatic deforestation in the Amazon Basin. Loggers have cut long paths into the forest, while ranchers have cleared large blocks for their herds. Fanning out from these clear-cut areas are settlements built in radial arrangements of fields and farms. Healthy

Earth As Art image The Optimist
August 1, 2000

The Optimist

On the edge of the Kalahari Desert in Namibia, sand dunes are encroaching onto once-fertile lands in the north. Healthy vegetation appears red in this image; in the center, notice the lone red dot. It is the result of a center-pivot irrigation system, evidence that at least one optimistic farmer continues to work the fields despite the approaching sand.

Earth As Art image Parana River Delta
May 1, 2000

Parana River Delta

The Parana River delta is a huge forested marshland about 32km northeast of Buenos Aires, Argentina. The area is a very popular tour destination. Guided boat tours can be taken into this vast labyrinth of marsh and trees. The Parana River delta is one of the world's greatest bird-watching destinations. This image highlights the striking contrast between dense forest and

A Landsat 7 SLC-off Scene Example

A Landsat 7 SLC-off Scene Example

A Landsat 7 SLC-off Scene Example

Rocket taking Landsat 7 to space

Rocket taking Landsat 7 to space

Landsat 7 heading to space after launch April 15, 1999. 

SLC-Off showing showing satellite image with parallel bands of missing image; and SLC-On gap mask with correlating blue bands.

Sample SLC-Off to SLC-On gap mask

Left: Sample SLC-Off image; Right: SLC gap mask