For example, a single-band, grayscale, aerial image records wavelength data extending over much of the visible portion of the electromagnetic spectrum therefore, it has a low spectral resolution. Other considerations include the number and placement of bands covering an interval of the electromagnetic spectrum. The higher the spectral resolution, the narrower the wavelength range for a particular band. Spectral resolution describes the ability of a sensor to distinguish between wavelength intervals in the electromagnetic spectrum. The first graphic below represents a higher spatial resolution than the third graphic. Higher spatial resolution allows you to resolve and analyze smaller ground objects. A higher spatial resolution implies that there are more pixels per unit area. In this case, resolution refers to the pixel size - the area covered on the ground and represented by a single pixel. In a GIS, the spatial resolution of an image dataset is important, especially when displaying or comparing raster data with other data types, such as vector. When working with image raster data, there are four types of resolution: spatial resolution, spectral resolution, temporal resolution, and radiometric resolution. The size of the resultant database compared to disk capacity.The application and analysis to be performed based on the minimum mapping unit.The spatial resolution of the input data.This may increase analysis processing speed.Ĭonsider the following when specifying the pixel size: You can store a copy of the data at its smallest and most accurate pixel size while resampling it to match that of the largest and least accurate pixel size.

An image dataset can be resampled to have a larger pixel size however, resampling an image to have a smaller pixel size does not produce greater detail. Spatial resolution is compared to information content.ĭetermining an adequate pixel size is as important in planning an application based on remote sensing as determining which datasets to obtain. The more homogeneous an area is for critical variables, such as topography and land cover, the larger the cell size can be without affecting accuracy.

If you're using a classified dataset derived from 30-meter resolution satellite imagery, using a digital elevation model (DEM) or other ancillary data at a higher resolution, such as 10 meters, may be unnecessary. Essentially, in a GIS, the results are only as accurate as the least accurate dataset.

When choosing an appropriate pixel size, balance the desired spatial resolution-based on the minimum mapping unit of the ground features you need to analyze-with practical requirements for quick display, processing time, and storage. Small pixel sizes are compared to large pixel sizes.

This requires greater storage space, which often results in longer processing time. However, smaller pixel sizes result in larger raster datasets to represent an entire area. More objects on the ground, smaller objects, or greater detail in the extents of ground features can be represented by an image with a smaller pixel size. The pixel must be small enough to capture the required detail but large enough to facilitate computer storage and analysis efficiencies. The level of detail (of objects and phenomena) represented by an image is often dependent on the pixel (cell) size, or spatial resolution, of the image.

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