Angle files

Under certain circumstances, there can be discontinuities in the sensor zenith and azimuth bands generated by these tools. The more widely used solar angle bands which are used to perform per-pixel solar corrections for Top-of-Atmosphere TOA reflectance conversion are impacted, though it is less visible. Collection 1 Landsat 8 data products are not impacted by this issue.

This has been corrected in Landsat Collection 2 and will not impact the angle bands which are bundled as part of the Collection 2 Level-1 products. The Landsat Angles Creation Tool has been updated to correct for this issue. Users of these tools, particularly those who rely upon the sensor viewing angles, should download and use the updated versions of these tools. The following technical details determine the outcome of the view angle bands for the product in which they are generated:.

Users may find this information useful in the form of X-Y-Z vector directions. Storing this information as two angles, rather than as three vector components, reduces the size of the data set associated with this information and makes it more manageable from both a storage and distribution standpoint.

The angle bands allow the user to better understand how the sensor viewing geometry and solar illumination geometry affect the object being sensed by the instrument. One impact to the calculated zenith angles is the curvature of the Earth. Figure 3 demonstrates the curvature by showing how the local vertical axis changes as the object being viewed moves away from nadir with respect to the satellite. The curvature of the Earth causes the z-axis to fall farther away from the nadir viewing vector of the satellite.

This curvature has a measurable effect on the zenith viewing angles. The sensor focal plane architecture also plays a role in defining the output of the angle bands. The 7 even SCAs 2 through 14 are arranged to point slightly aft. The detectors within the focal plane are in parallel rows, one column covering the along track swath width of a single scan, with the odd, even detectors and the bands separated in the along scan direction.

The Landsat TM focal plane layout is very similar, minus the set of panchromatic band detectors, and the thermal band would contain 4 detectors rather than 8. The along-track distribution of the spectral bands causes the viewing angles to be different for each spectral band. The combination of these effects, the along-track offsets for each band, and the along-track and across-track offsets for each SCA, creates a set of azimuth angles that alternate in value per SCA.

The effect of projecting the sensor Line-of-Sight LOS vector into the local coordinate system causes the azimuth angles to change discontinuously for adjacent SCAs see Figure 5. The alternating pattern within the azimuth satellite viewing angle band and the light to dark transition at the center of the image are the result of the SCA pushbroom sensor of Landsat 8. The darker to lighter transition from the center of the zenith angle band to the outer edges is due to the local coordinate system having its z-axis normal to the surface of the Earth ellipsoid.

As a final demonstration of these effects, sample coordinate profiles display for both the azimuth and zenith angles see Figure 7. The y-axis of the profile plots are in units of hundredths of degrees. Transitions between the SCAs can be seen in both sets of profiles, however, the changes are much more pronounced in the azimuth angle profile.

For the sensor azimuth angle the effect of projecting the sensor LOS vector into the local coordinate system causes the azimuth angles to change discontinuously only when the mirror transverses the location directly nadir to the spacecrafts position see Figures 8 and 9. Figure 10 shows sample profiles of the sensor viewing images. Time dependencies occur during an acquisition, as both the satellite and sun viewing angles vary within a given scene.

For the same reason that each SCA has its own unique viewing angle, each SCA of each band views the same object on the ground at slightly different times. This time delay between bands of the SCAs causes the sun and satellite viewing angles to differ as a given object is viewed by each band and SCA during an acquisition; therefore, the satellite and sun positions associated with the object are different.

Latest Earthquakes Chat Share. The Landsat Collection 1 Angle Coefficient file provides sensor viewing angle model coefficients that can be used to create angle bands, and allows users to compute the solar and sensor viewing angles on a per-pixel basis. Land Cloud Cover, which is also included, is determined by calculating the percentage of clouds over land-only pixels in a scene using a mask that Definitive Ephemeris is used for geometrically correcting Landsat 7 data and providing improved accuracy over predicted ephemeris.

Landsat Calibration Parameter Files CPFs provide radiometric and geometric coefficients needed for processing of raw, uncorrected Landsat image data into Level-1 data products. Over 15, coefficients are issued to span distinct timeframes and are updated with improved calibration coefficients.

CPFs are often updated with improved coefficients. Learn more and search CPF files : Landsat The highest quality Level-1 products suitable for pixel-level time series Formulas for these conversions are on the Using Science Explorer. Mission Areas. Unified Interior Regions. Science Centers. Frequently Asked Questions. Educational Resources. Multimedia Gallery. Web Tools. Filed under Liquid Biopsy.

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