If an image is properly calibrated, values of the pixels in the image of a star divulge its temperature and magnitude. To calibrate an image the value of a quantity that is measurable in pixels must be known. The pixel or pixels representing this quantity are assigned the known value. All other measurements for the same unit of measure will then have a value relative to the known value. If pixel values in an image of the ocean surface are each assigned a color, then patterns in the movement of warm and cold water temperatures of the ocean can be detected visually.
Land elevation is easier to interpret using visual images.
It is easier to understand some data by analyzing an image, rather than by looking at written numbers. Any data which can be represented in a two dimensional rectangular array of numbers, can also be visually represented in an image. NIH Image is Macintosh software in the public domain. It was developed by the Research Services Branch of the National Institute of Mental Health, a section of the National Institutes of Health. A copy of the software, as well as support software, may be downloaded from links at this web site.