ESDU Engineer

Carpet Plots

The use of “carpet plots” to represent graphical data has been widespread in aeronautics for at least half a century. However, it is common experience that, “no one is ever taught about carpets – you just pick it up”. In keeping with this background, it is not a great surprise to find that most published references to carpets are over fifty years old.

It is hoped that this lack of guidance will be overcome following the issue of ESDU Data Item No. 04008, “Use of carpet plots to represent functions of two variables”. This Item has been issued into the ESDU Aircraft Performance Series but may be accepted for inclusion in other Series.

The Data Item illustrates the problems that can arise with conventional 2-dimensional plots and shows how these are overcome by use of carpet plots. The sketches included with this article are taken from the Item and show these distinctions. Overall, the Item contain 23 sketches that show the various forms that carpets can take together with advice on methods of construction and layout.

In the final Section of the Item the concept of the carpet plot is extended to the “lattice” plot which can represent the behaviour of a function of three independent variables. Two examples of lattices are given to show how they may be constructed and how they are used to interpolate between values of all three variables.

Queries regarding this article should be directed to the Performance Group via esdu@ihsesdu.com or the ‘feedback’ form at www.ihsesdu.com.