What is Apparent reflectance?

At the sea Level, apparent reflectance, also called, diffuse reflectance, is the ratio of the upwelling irradiance to the downwelling irradiance below the water surface, R(0-).

What is DN in arcgis?

ArcMap 10.3. This function adjusts image brightness digital number (DN) values for some satellite sensors, similar to an atmospheric correction. The adjustments are based on sun elevation, acquisition date, and sensor properties (gain/bias settings for each band).

What is radiometric correction in Arcgis?

Radiometric correction requires that the user account for the radiometric error that occurs within a specific scene, including the sun elevation, atmospheric conditions (depending on the sensor), and the metadata for each sensor across all of the time intervals you intend to measure.

Why do we do atmospheric correction?

If you only have a single image, atmospheric correction is only necessary if the image is very hazy. Atmospheric correction removes the scattering and absorption effects from the atmosphere to obtain the surface reflectance characterizing (surface properties).

What is TOA radiance?

Radiance, Reflectance, and Top of Atmosphere (TOA) Radiance includes the radiation reflected from the surface, in addition to the radiation that bounces in from neighboring pixels, and the radiation reflected from clouds.

How do you calculate reflectance from DN value?

First compute Spectral radiance for kth band using formula: Radk = (DN*SRk)/1024. Here the SR denotes the Saturation Radiance.

How do you find radiometric resolution?

While the arrangement of pixels describes the spatial structure of an image, the radiometric characteristics describe the actual information content in an image. Every time an image is acquired on film or by a sensor, its sensitivity to the magnitude of the electromagnetic energy determines the radiometric resolution.

What is radiometric correction of satellite image?

One of the essential processes for satellite images radiometric correction is the conversion of digital number to radiance (or reflectance) values. This process is necessary if measurements are taken from multiple sensing platforms such as the combination of Landsat-5, 7, 8 and Sentinel-2.

What is absolute atmospheric correction?

Absolute correction take into account the atmospheric conditions at the same time of satellite overpass and aims to acquire absolute reflectances based on the acquisition time of the image. As output, FLAASH produces a surface reflectance (Rsup) image.

Why is atmospheric correction difficult?

11.3. Atmospheric correction of satellite measurements over inland water is challenging due to many factors. Some of the major challenges include terrestrial atmospheric pollution, high turbidity, floating objects, and the adjacency effect of neighboring land pixels, which significantly raise the reflectance of water.

What are the values of the apparent reflectance function?

Checked—The function returns 32-bit floating-point values, which most commonly are in the range of 0.0 to 1.0. No data clipping is performed if this option is selected. Since the output data type for albedo is floating point, you must explicitly set the preferred Output Pixel Type to either 32-bit float or 64-bit double.

How does apparent reflectance work on a satellite?

The Apparent Reflectance function is used to adjust reflectance, or brightness, values of some satellite imagery based on the scene illumination and sensor-gain settings. The images are adjusted to a theoretically common illumination condition, so there should be less variation between scenes from different dates and different sensors.

How does the apparent reflectance function in ArcGIS work?

The calibration uses sun elevation, acquisition date, sensor gain and bias for each band to derive Top of Atmosphere reflectance, plus sun angle correction. The Apparent Reflectance function is used to adjust reflectance, or brightness, values of some satellite imagery based on the scene illumination and sensor-gain settings.

How to convert Toa radiance to apparent reflectance?

The second calibration is to convert the TOA radiance to apparent reflectance, based on sun elevation and acquisition date. The formulas used in the two conversions can be found in section 11.3.1 and 11.3.2 of the Landsat 7 Science Data User Handbook. Apparent reflectance is a ratio and its native output range is 0-1.