1. A method for updating a legend of a spatial display for use with graphical user interface of a field computer linked to one or more sensors for sensing data or information from a piece of equipment performing an agricultural operation, said method comprising: a) providing a field computer with a graphical user interface; b) providing at least one sensor operatively linked to said field computer; c) providing a piece of equipment performing an agricultural operation and in operative communication with said at least one sensor for sensing data or information for display on said graphical user interface; d) calculating an average value for said data; e) assigning one or more range values to a legend wherein said range values are centered about said average; f) displaying a spatial representation of a geographic location wherein said display is coded to associate said range values with corresponding locations on said spatial representation of a geographic location; and g) updating said legend based upon a predefined criteria.