## 1 Introduction  
Information protection is one of the aspects of everyday human life. When processing information, particular attention is paid to network security [1, 2], security of data processed in paper form, or protection of data carriers held [3]. It should be noted, however, that data processing (e.g., printing, displaying) occurring in electronic form poses a great risk related to the loss of this data in a non-invasive manner [4, 5, 6]. The reason for such a phenomenon is the formation of electromagnetic emissions, the distinctive features of which may allow the reconstruction of protected data [7, 8, 9, 10]. The hazards related to the formation of electromagnetic revealing emissions are analyzed primarily in terms of the sources of these emissions in the graphic tracks. This is due to the possibility of direct presentation of the obtained information in the form of images containing the processed data. In particular, the sources of such emissions may be computer monitors, displays of multifunction devices or in a simpler form--displays of laser printers, graphic layouts of printing devices, and all kinds of data displays [11; 12; 13; 14]. The process of non-invasive data acquisition based on electromagnetic emissions does not end with sampling and recording such signals. In order to display the information properly, the correct raster parameters are necessary, i.e., the length of the horizontal line of the reconstructed image and the number of lines (image height) making up a given image. These parameters should be consistent with the parameters of the original image [15; 16; 17; 18]. The issue related to the determination of raster parameters can be considered in several variants. The first is laboratory tests. During such tests, personnel can access the infiltrated device [19; 20; 21; 22; 23]. However, depending on the device under test, knowing the parameters of the displayed image may not be obvious. While in the case of computer monitors it is not too difficult, in the case of other displays, e.g., multifunction devices, the process of getting to know the display's operating mode can be a big problem. The second variant is the study of an unknown object. This concerns operational activities under real conditions. Then it is not possible to know the raster parameters, even of a typical computer monitor. The determination of the value of these parameters must be supported by appropriate algorithms that will allow for the automation of the process [24; 25; 26; 27; 28; 29]. Many publications applying to the electromagnetic infiltration process and the non-invasive acquisition of information present the analysis of threats related to the above-mentioned phenomenon and the possibilities of data recovery based on the recorded signals of revealing emissions [30; 31; 32; 33]. In these publications solutions that can effectively protect data against electromagnetic infiltration are presented. In the case of sources of revealing emissions in the form of graphic paths, the analyzes performed are based on images that give the impression of being \"aligned\", i.e., for the correct value of the image line length. There is no mention of how this value was estimated and with what accuracy. The most important issue is to visualize the obtained data and show the reader the essence of the threat. The article presents the possibilities of determining the length of the horizontal line of the image for the case defined as operational activities, i.e., the lack of knowledge of the geometrical parameters of the reconstructed image. The starting point is a rough determination of the image line length on the basis of, for example, the analysis of the emission signal in the time or frequency domain, e.g., the Chirp-Z transform [34; 35]. This is possible due to the periodic repetition of characteristic image elements in the aforementioned waveform. These are, for example, pulses correlated with the horizontal synchronization signal of a computer monitor.