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Resolution : Satellite Imagery

The resolution of satellite imagery is the main selling point for satellite operators. This, however, is not the only feature to consider. Accuracy is also important in determining image quality, and it’s critical to understand the distinction between resolution and accuracy.

Although high-resolution is frequently associated with high-accuracy (and vice versa), this is not always the case. This distinction is critical to keep in mind when purchasing satellite imagery.

The smallest size an object or detail can be represented in an image is referred to as resolution. Higher resolution means smaller pixel sizes, which means more detail. For example, satellite imagery with a resolution of 30cm by 30cm can capture details on the ground that are greater than or equal to 30cm by 30cm. Anything less than that size on the ground will be blended in with the surrounding area to form a 30cm by 30cm square.

The resolution of a sensor affects how it can be used. The resolution of a satellite can vary depending on its orbit and sensor design. For any dataset, there are four types of resolution to consider: radiometric, spatial, spectral, and temporal.

A. Radiometric resolution

It is the amount of information contained in each pixel, i.e. the number of bits representing the energy recorded. Each bit stores a power 2 exponent. A sensor with an 8 bit resolution, for example, has 256 potential digital values (0-255) to store information. As a result, the higher the radiometric resolution, the more values are available to store information, allowing for better discrimination of even minor differences in energy.

B. Spatial resolution

It is defined by the size of each pixel in a digital image and the area on Earth’s surface that pixel represents.

The more detail you can see, the finer the resolution

C. Spectral resolution.

is a sensor’s ability to distinguish finer wavelengths, i.e. having more and narrower bands. Many sensors are multispectral, which means they have three to ten bands.

Some sensors, known as hyperspectral, have hundreds or even thousands of bands. The finer the spectral resolution, the narrower the range of wavelengths for a given band.

D. Temporal resolution

is the amount of time required for a satellite to complete an orbit and return to the same observation area. This resolution is determined by the orbit, sensor characteristics, and swath width. Because geostationary satellites rotate at the same rate as the Earth, the temporal resolution is much finer.

Polar orbiting satellites have a temporal resolution ranging from one day to sixteen days.

Resolution Satellite Imagery

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