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University of Nebraska–Lincoln

A raster grid can be made simply by overlaying a piece of graph paper over an image. Now, with the graph paper in place one can see that each small square section of the image has an exact location. The small sections are called pixels. The pixel's location is identified by giving its x and y coordinates. When working with various software packages, the point of origin for the coordinates may vary. Even though the point of origin varies, each pixel will still have a specific location.

  • ---Pixel x=5 y=1

Each of the pixels is assigned a number value that corresponds to the amount of energy that is reflected by the surface located under that pixel. The number values range from 0 (very low reflectivity) to 255 (very high reflectivity).

Raster Activities