the present invention will now be described with reference to the accompanying drawings , wherein the same or similar elements are identified with the same reference numeral . the print system as shown in fig1 is an example of a print system wherein the invented method is applicable . this system comprises a number of work stations 1 that are configured to dispatch print jobs over network n to a print controller , or digital front end , 2 , that assembles the print jobs and schedules them for processing on printer 3 . alternatively , the controller 2 may be connected to multiple print engines , each configured for particular print jobs . print engine 3 is a wide format printer , having multiple media rolls 4 . each medium is calibrated separately with respect to accurate medium transport depending on the medium type . local user interface 5 is used to start and stop a calibration procedure for a freshly introduced medium . not shown is the embedded cpu that controls the behaviour of the print engine 3 . in fig2 the transport of a recording medium in the print engine is shown . medium 10 is transported in the transport , or subscanning , direction 11 . a carriage 17 that comprises a number of printheads ( not shown ) and an optical capturing element 18 reciprocates in a direction perpendicular to the transport direction across the recording medium . a paperstep in the transport direction 11 is made during a movement reversal of the carriage . alternatively , in the case of monodirectional printing , it occurs during a reverse movement of the carriage , but in any case , the medium is only transported at a time that no ink is applied to the medium 10 . the print surface 16 defines the position of the print medium relative to the printheads in the carriage . in the case thick media are applied , the height of the print surface may have to be adjusted to maintain a predetermined distance between the printheads and the medium surface . the transport roller 12 is hard surfaced and defines the position of the medium in transport direction . roller 13 is soft surfaced and pinches the medium onto the surface of the transport roller 12 . the medium is transported by rotating transport roller 12 which is driven by drive motor 14 through an intermediate worm gear 15 . in this embodiment , the transport roller has a diameter of 81 . 65 mm . a full revolution of this roller transports the medium across a distance of fr = 256 . 5 mm . this is effected by nf = 60 full revolutions of the drive motor and worm gear , resulting in a basic stepsize of fr / 60 = 4 . 275 mm . fig3 shows the basic pattern of a measurement of a paperstep error . on the recording medium six markers are printed in sets of three markers . step k at 21 indicates a swath k wherein a single printhead prints three markers on one side of the medium and three markers on an other side of the medium , the printhead moving in either one direction 20 . after finishing the swath , the recording medium is transported in direction 11 , applying a predetermined nominal paperstep . in a next swath , step k + 1 , the markers are printed once more , thereby placing one marker inbetween two previously printed markers . the optical capturing element 18 is configured to provide a digital image of an optical swath 22 , which is more narrow than a print swath . from this digital image , a difference in the position of the neighboring markers 23 is derived , which can be determined very accurately by correlation techniques . this provides a paperstep error associated with the nominal paperstep in this particular position of the transporting components . a medium slip between the transport roller and the medium is disregarded in this analysis . in a calibration procedure , two nominal papersteps are applied : one equal to the basic step size of fr / 60 and one slightly larger than that , fr / 53 . the cyclic disturbance is assumed to be of the form u ⁡ ( x ) = ∑ i = 1 n ⁢ a ⁡ ( i ) ⁢ sin ⁡ [ 2 ⁢ πω ⁡ ( i ) ⁢ x fr + ϕ ⁡ ( i ) ] , ( 1 ) wherein x is a distance along the circumference of the transport roller , a ( i ) is an amplitude , ω ( i ) is a periodicity of the disturbance , φ ( i ) is a phase of the disturbance , and i = 1 , . . , n is an index , indicating a specific contributing periodic function . n is the number of these functions that are considered to be involved in the disturbance approximation . after step k ( k = 1 , . . , k ), the distance x is : wherein step ( k ) is one of the two nominal papersteps and x ( 0 )= 0 . a good working selection of papersteps is an alternating one from the two applicable stepsizes , but alternative selections are very well possible . a step error in step k is expressed as a relative position deviation a ⁡ ( i ) ⁢ sin ⁡ [ 2 ⁢ πω ⁡ ( i ) ⁢ x ⁡ ( k ) fr + ϕ ⁡ ( i ) ] = α ⁡ ( i ) ⁢ sin ⁡ [ 2 ⁢ πω ⁡ ( i ) ⁢ x ⁡ ( k ) fr ] + β ⁡ ( i ) ⁢ cos ⁡ [ 2 ⁢ πω ⁡ ( i ) ⁢ x ⁡ ( k ) fr ] , ( 4 ) ⁢ a ⁡ ( k , i ) = sin ⁡ [ 2 ⁢ πω ⁡ ( i ) ⁢ x ⁡ ( k ) fr ] - sin ⁡ [ 2 ⁢ πω ⁡ ( i ) ⁢ x ⁡ ( k - 1 ) fr ] , ⁢ ⁢ and ( 5 ⁢ a ) ⁢ b ⁡ ( k , i ) = cos ⁡ [ 2 ⁢ πω ⁡ ( i ) ⁢ x ⁡ ( k ) fr ] - cos ⁡ [ 2 ⁢ πω ⁡ ( i ) ⁢ x ⁡ ( k - 1 ) fr ] , ( 5 ⁢ b ) the measurements after step k are represented by m ( k ). the parameters α ( i ) and β ( i ), i = 1 , . . , n determine the solution of the problem , given a set of n frequencies . for the above - mentioned system , a set of n = 32 frequencies of { 1 , 2 , . . . , 29 , 60 , 120 , 180 } are used , leaving 64 parameters to be found . a frequency of 1 corresponds to a full revolution of the roller . a minimum of 64 measurements is necessary to determine the required parameters . a larger number of measurements may be performed to improve the robustness of the solution to this mathematical problem , which is solved by a known method as described by k . j . aström and b . wittenmark in computer control systems , 1984 , p . 328 . the contributions of the three highest frequencies to the cyclic disturbance would not have been found using a single step size of fr / 60 . a table for relating an actuation signal to a medium displacement is generated based on the finite series ( 1 ) using the found parameters . a second calibration procedure applies a randomly selected step size inbetween fr / 60 and fr / 30 , based on a signal reconstruction method called compressive sampling . the same mathematical framework as in example 1 is applied , with the difference that a number of addtional steps are applied to determine a set of relevant frequencies . in the specific system described above , the step sizes are randomly selected using a step size discretisation of fr / 1515 . this determines a maximum frequency that can be identified of 1515 / 2 = 707 . 5 . to further enhance the speed of the procedure , a limited set of possible frequencies is used . in this example , only 1200 frequencies of the set { 0 . 1 , 0 . 2 , 0 . 3 , . . . , 120 . 0 } are taken into account . the number of measurements again determines the obtained accuracy . a sufficient accuracy has been obtained by using 370 relative position measurements , which resulted in a 370 times 2400 matrix describing the relation between possible relevant calibration parameters and the relative error . using the gauss - dantzig procedure ( e . j . candes , t . tao , annals of statistics , vol . 35 ( 6 ), 2007 , page 2313 - 2351 ) the limited ( sparse ) number of relevant parameters is identified . thereby also the relevant frequencies ω ( i ) are estimated from the measurement data . the gauss - dantzig procedure requires to specify a threshold to set sufficiently small parameters to zero . this allows dealing with the influence of noise in the measurements . the threshold in this example has been set to 1 micrometer , corresponding to a standard deviation of the measurement error . in an instance of the aforementioned paper positioning system , the procedure was successful in identifying a set of relevant frequencies as { 1 , 2 , 3 , 23 , 60 , 71 }. three frequencies were artificially introduced in the actuation of the paper positioning system . phase and amplitude of these frequencies were identified accurately . in another embodiment , 400 relative position measurements were used . this number corresponds to 10 full revolutions of the transport roller , since the average step size is 1 . 5 * fr / 60 . the 10 full revolutions correspond to the minimum frequency in the list of frequencies that are used for this system . a balance is struck between the number of measurements and the required accuracy , not only in order to limit the computational effort , but also to limit the amount of medium that is used in the calibration procedure . using the parameters found for the experimental data , a table of actual papersteps is constructed for every discrete value of the actuation signal for a full rotation of the transport roller . besides yielding a more accurate determination of this table , the provided method enables the use of print strategies that require a paperstep different from an integer number of a basic step size . a third procedure based on this invention has been developed for a situation of a local deformation on the surface of the transport roller , for example due to a small counter roller pressing on the same position on the transport roller for a long period of time . dependent on the quality of the transport roller material , in particular its resistance to plastic deformations , a dimple may occur , having a smaller size along the circumference of the roller than the basic stepsize , corresponding to a full revolution of the driving elements . in particular , when a transport roller is returned to a default stand - by position , a fixed dimple position has been observed . the depth of this dimple has an effect on the accuracy of the medium displacement and it is not possible to sample this dimple by using basic stepsizes only . thus , a second stepsize is used , in addition to a basic stepsize d = fr / n , wherein fr = πd is the circumference of the transport roller , d is the average diameter of the transport roller and n the number of full rotations of the driving elements to obtain one single full rotation of the transport roller . this stepsize d ′ is selected such that an integer number n ′ of these stepsizes equals slightly more than a full rotation of the transport roller . this is expressed in the equality n ′ ⁢ d ′ = fr + 1 m ⁢ d = fr ⁡ ( 1 + 1 nm ) , ( 7 ) wherein m is the number of samples that is used to scan the dimple , or , in other words , the number of full rotations of the transport roller that is made before returning to an indexed position . in general , n ′ may be different from n , but in practice often the same value is used . the local deformation correction is calculated by using a sum of gaussian functions fit or a sum of high frequency sinusoidal functions fit . a window mask is used when more than one local deformation or dimple is present in the roller . this is done to isolate the effect of each dimple . the invention being thus described , it will be obvious that the same may be varied in many ways . such variations are not to be regarded as a departure from the spirit and scope of the invention , and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims .