A device for use in monitoring operation of a system asset comprising a device or a machine, said device comprising: a display device ; and a processor coupled to said display device , said processor configured to: display, on said display device , a first plot of a plurality of graphical plots of a first operation characteristic of the system asset as a function of a second operation characteristic in response to a user selection to display the first plot of the plurality of graphical plots; display, on said display device , a reference graphical plot of the first operation characteristic of the system asset as a function of the second operation characteristic overlying the first plot of the plurality of graphical plots, wherein the reference graphical plot is based on expected or predicted performance of the system asset based on a manufacturer's specifications for the particular system asset ; and maintain the display of the reference graphical plot on said display device when the user selects a second plot of the plurality of graphical plots, the reference graphical plot displayed overlying the second plot; receive a selection of one or more points on the selected measurement plot about which the user desires detailed information; and display a representation of the difference between the first operation characteristic and the reference graphical plot at the selected value of the second operation characteristic. a display device ; and a processor coupled to said display device , said processor configured to: display, on said display device , a first plot of a plurality of graphical plots of a first operation characteristic of the system asset as a function of a second operation characteristic in response to a user selection to display the first plot of the plurality of graphical plots; display, on said display device , a reference graphical plot of the first operation characteristic of the system asset as a function of the second operation characteristic overlying the first plot of the plurality of graphical plots, wherein the reference graphical plot is based on expected or predicted performance of the system asset based on a manufacturer's specifications for the particular system asset ; and maintain the display of the reference graphical plot on said display device when the user selects a second plot of the plurality of graphical plots, the reference graphical plot displayed overlying the second plot; receive a selection of one or more points on the selected measurement plot about which the user desires detailed information; and display a representation of the difference between the first operation characteristic and the reference graphical plot at the selected value of the second operation characteristic. display, on said display device , a first plot of a plurality of graphical plots of a first operation characteristic of the system asset as a function of a second operation characteristic in response to a user selection to display the first plot of the plurality of graphical plots; display, on said display device , a reference graphical plot of the first operation characteristic of the system asset as a function of the second operation characteristic overlying the first plot of the plurality of graphical plots, wherein the reference graphical plot is based on expected or predicted performance of the system asset based on a manufacturer's specifications for the particular system asset ; and maintain the display of the reference graphical plot on said display device when the user selects a second plot of the plurality of graphical plots, the reference graphical plot displayed overlying the second plot; receive a selection of one or more points on the selected measurement plot about which the user desires detailed information; and display a representation of the difference between the first operation characteristic and the reference graphical plot at the selected value of the second operation characteristic. <EOS>