METHOD FOR IDENTIFYING SLOW TRANSIENT VARIATIONS AND/OR LOCAL SPATIAL VARIATIONS OF A PHYSICAL PROPERTY IN A SET OF DATA POINTS

The invention concerns a method for identifying slow transient variations and/or local spatial variations of a physical property in a set of data points, the method comprises the steps of: A) obtaining (10) a first set of data points (t), wherein each of said data points is associated with at least i) a point of time, ii) a position in at least two dimensions and iii) a value representing a physical property, wherein the data points in each position are separated in time by a sampling time step (Δt), and wherein the first set of data points represents a total time period (t); B) calculating (20) a temporal filtered value of the representation of the physical property for at least a portion of the first set of data points distributed over the total time period (t), wherein the temporal filtered value is based on a plurality of values of the representation of the physical property in the same position obtained over an effective filtering time period (Δt) covering a plurality of data points, wherein the effective filtering time period (Δt) has a certain time relation to the data point (t) for which the calculation is carried out and wherein the effective filtering time period (Δt) is considerably longer than an average sampling time step (Δt) and considerably shorter than the total time period (t): C) combining (30) at least a portion of the calculated temporal filtered values of the representation of the physical property with the point of time and position of the corresponding data point in the first set of data points so as to obtain a second set of data points where each value representing the physical property is the temporal filtered value; and D) analysing (40) in time sequence the second set of data points over at least a portion of the total time period (t).