Spectral resolution calculator1/4/2023 ![]() ![]() If a sensor has a spatial resolution of 20 metres and an image from that sensor is displayed at full resolution, each pixel represents an area of 20m x 20m on the ground. It is important to distinguish between pixel size and spatial resolution - they are not interchangeable. Image pixels are normally square and represent a certain area on an image. However, smaller features may sometimes be detectable if their reflectance dominates within a articular resolution cell allowing sub-pixel or resolution cell detection.Īs we mentioned in Chapter 1, most remote sensing images are composed of a matrix of picture elements, or pixels, which are the smallest units of an image. ![]() If the feature is smaller than this, it may not be detectable as the average brightness of all features in that resolution cell will be recorded. For a homogeneous feature to be detected, its size generally has to be equal to or larger than the resolution cell. This area on the ground is called the resolution cell and determines a sensor's maximum spatial resolution. The size of the area viewed is determined by multiplying the IFOV by the distance from the ground to the sensor (C). The IFOV is the angular cone of visibility of the sensor (A) and determines the area on the Earth's surface which is "seen" from a given altitude at one particular moment in time (B). Spatial resolution of passive sensors (we will look at the special case of active microwave sensors later) depends primarily on their Instantaneous Field of View (IFOV). The detail discernible in an image is dependent on the spatial resolution of the sensor and refers to the size of the smallest possible feature that can be detected. ![]()
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