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Sensor Evaluation: Resolution Comparison



Satellite sensors are designed with a variety of temporal, spatial, and spectral characteristics and resolutions. Remotely sensed data may be acquired on an as needed basis, such as monthly, or hourly, depending on the frequency of changes of interest. Spectrally, data may be panchromatic (gray scale imagery or black and white photography), multispectral (several channels; e.g., blue, green, red, near-infrared), or hyperspectral (hundreds of channels). The spectral type used in a given application depends on the spectral response of the observed surface. These two types of resolution are more readily understood than spatial resolution, which is the physical area of the ground represented by each picture element, or pixel, in the image. As the pixel size increases (e.g., 10 to 30 m), the same image size (e.g., 100x100 pixels) will show a larger area on the ground. If the pixel size increases and the same area on the ground is displayed, then the image will get smaller and will have to be magnified to appear to be the same size.

Examples of how the image area differs with changes in image spatial resolution are divided into two sets: 1 - 30 m and 30 - 1000 m. The images using the range of spatial resolutions from 1 - 30 m were derived from a set of 1-m ARTIS (airborne) images. In the range 30 - 1000 m, the images were derived from a 30-m Landsat Thematic Mapper image of the San Francisco Bay area. Most of the images are multispectral (false color-infrared), with one panchromatic 1-m image.

Image pixel size changes can be viewed as well as a segment of the 1-m image is resampled and magnified to 30-m resolution.


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