Image Resolution in Remote Sensing

• Resolution refers to potential details provided by imagery.
• Resolution is defined as a measure of the ability of an optical system of other sensor to distinguish between signals that are spatially near or spectrally similar.
• Resolutions should be understood by the analyst in order to extract meaningful biophysical or hybrid information form the remotely sensed imagery.
• Following are the 4 types of Resolutions commonly used in Remote Sensing:

  1. Spatial Resolution
  2. Spectral Resolution
  3. Temporal Resolution
  4. Radiometric Resolution
1. Spatial Resolution

• Spatial Resolution is a measure of the smallest object that can be resolved by the sensor, or the ground area imaged for the instanton.
• Spatial resolution is ability to distinguish between two closely spaced objects on an image.
• Spatial resolution depends on the field of view (FOV), altitude and viewing angle of a sensor.
• Spatial Resolution describes how much detail in a photographic image is visible to the human eye.
• The ability to “resolve”, or separate, small details is one way of describing what we call spatial resolution.
• Spatial resolution of images acquired by satellite sensor systems is usually expressed in meters.

Image by vectorjuice on Freepik

2. Spectral Resolution
• Each bands records a specific portion of the electromagnetic portion.
• Spectral resolution refers to the specific wavelength intervals in the electromagnetic spectrum that a sensor can record.
• Narrower bands have higher spectral resolution.
• The spectral resolution describes the number and width of spectral bands in a sensor system.
• Spectral responses from the ground targets are recorded in separate spectral bands by sensors.
• Broad classes, such as water and vegetation, can usually be separated using very broad wavelength ranges- the visible and near infrared. Other more specific classes, such as different rock, types, may be easily distinguishable using either of these broad wavelength ranges and would require comparison at much finer wavelength ranges to separate them. Thus, we would require a sensor with higher spectral resolution.

3. Temporal Resolution
• Temporal resolution is a measure of the repeat cycle frequency with which a sensor revisits the same part of the Earth’s surface.
• It finds the change in same part of the Earth after and before of the disaster.
• The temporal resolution depends primarily on the platform, for example, satellites usually have set return times and while sensors mounted on aircraft or unmanned aircraft systems (UAS), have variable return times.

4. Radiometric Resolution
• Number of shades or brightness levels at a given wavelength.
• Smallest change in intensity level that can be detected by the sensing system.
• Radiometric resolution is how finely a satellite or sensor divides up the radiance it receives in each band.
• Or, Radiometric Resolution is the measure of a Sensor’s ability to discriminate small differences in the magnitude of radiation within the ground area that corresponds to a single raster cell.

Featured image credit – Image by brgfx on Freepik

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