Gap Filling Landsat 7 SLC-OFF Images

PANCROMA is the Simple yet Powerful GIS software application for gap filling Landsat 7 SLC-Off images. Trial download PANCROMA gap filling or buy it now for only USD $49.95!

What is Gap Filling?

The Landsat 7 satellite suffered a partial failure in 2003 when its Scan Line Corrector (SLC) unexpectedly stopped operating. As the Landsat satellite orbits the earth a mirror scans side-to-side to collect the image data. Wedge shaped gaps are created as a result of the combination of orbital tracking and side-to-side sweeping. When it was working, the SLC corrected these gaps. The SLC failure has resulted in systematic gaps (black stripes) in every Landsat image collected since that time.

Can Anything be Done to Correct the Gaps?

Due to the nature of the failure, the gap data is not directly recoverable. However PANCROMA provides three algorithms to fill in the gaps in Landsat 7 images using data collected before the gap failure. The first (Transfer) method cuts data from pre-2003 Landsat images and transfers this information into the gap image after performing a global histogram match. The second, often more effective (Hayes) method uses a computational approach that synthesizes gap pixels by combining information in the gap image and a pre-2003 image. The third (TERAS) uses an alternative synthetic algorithm that usually produces the closest match of all.

How Effective are the PANCROMA Gap Filling Algorithms?

No gap filling technique is perfect, and the results are dependent on temporal and seasonal similarities between the source and target images, and variations of snow and cloud cover. However PANCROMA gap filling algorithms can produce remarkable corrections in many instances. Examples of gap filling results using TERAS are shown in the images below. The first shows the target image with gaps. The second shows the image after gap fill correction. The third shows the Adjust image used to fill the gaps. The fourth is a RGB color composite gap filled image.

[Gap Image]

[Gap Filled Image]

[Adjust Image]

[Gap Filled RGB Color Composite]

Before and After Gap Filling

Can I Pan Sharpen My Image After Gap Filling?

Yes. See the See the Pan Sharpening Landsat Gap Filled Images Tutorial on the White Papers link at this site.

Try PANCROMA Gap Filling for Yourself

Trial download PANCROMA gap filling or buy it now for only USD $49.95!

Use these Landsat Sample GeoTiff Band File Sets for Gap Filling in order to experiment with the gap filling routines. The zip file contains six images subsetted and matched using PANCROMA.

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