WO2000041423A1

WO2000041423A1 - Determining a transmitter radio-field coverage

Info

Publication number: WO2000041423A1
Application number: PCT/FR1999/003196
Authority: WO
Inventors: Eric Olivetan; Yves Theisen; Daniel Selecki
Original assignee: Telediffusion De France
Priority date: 1998-12-31
Filing date: 1999-11-17
Publication date: 2000-07-13
Also published as: FR2788132A1; EP1142397A1; AU1665200A; FR2788132B1

Abstract

The invention concerns a method whereby the radio-field of a transmitter (S) is measured in real points (PMRj) on a digitised geographical map. For each geographical point (PGi), a maximum variation (VGPi) of a physical quantity, altitude or radio-field, is determined (E4) about the point. The distance (Di) of a measuring point (PMi) nearest to the geographical point is evaluated (E5). A physical quantity interval containing the variation (VGPi) is sought (E6, E10) among several associated with distances. The geographical point (PGi) is rejected when said distance is less than the distance associated with the interval, or is accepted as fictitious measuring point (PMF) to increase the number of measuring points in an uneven zones. The radio-field in each geographical point is deduced (E12) from the fields at the real and fictitious measuring points and from the distances between them and the geographical point to visualise without aberration coverage zones.

Description

Determination of transmitter radio coverage

The present invention relates to the determination of the radio coverage around a radiofrequency transmitter within the framework of planning and simulation of radiocommunication, radio and television broadcasting networks. A geographic map on which is drawn at least the outline of the radio coverage is to be viewed on a screen or is to be edited.

The determination of the radio coverage around a transmitter uses the radio field values at real measurement points in the field around the transmitter and the characteristics of the site and of the signal emitted by the transmitter (see Article " CECILIA WEB, A WWW INTERFACE FOR THE CECILIA APPLICATION "by G. BOURLIER et al., IEEE 47 ^th Vehicular Technology Conference Proceedings, May 4, 1997, pages 1292-1294). In a predetermined processing region containing the measurement points, the radio field is determined at a given geographic point according to an algorithm based on values of the field measured in the field, the distance from this point to the measurement points and a propagation model of the signal sent from the transmitter depending on the relief around it. The algorithm is all the more efficient as the density of the measurement points in the processing region is high, and more precisely as the density of the measurement points around the given geographical point is high. When the measurement points are few in a relatively large or uneven area in the treatment region, digital aberrations on the radio field values in the area appear.

The present invention aims to remedy the aberrations mentioned above by creating "fictitious" measurement points inside the relatively deserted areas of real measurement points. For example in hilly, mountainous areas, the fictitious measurement points increase the density of the measurement points on which the radio field at geographic points in the area is determined according to the invention.

To this end, a method for determining the radioelectric coverage of a transmitter on a geographic map, comprising measurements of the radioelectric field emitted by the transmitter at real measurement points, is characterized by the following steps for each geographic point: determining a maximum variation of a physical quantity within a predetermined radius around the geographical point,

- search for a measurement point closest to the geographical point and assess the distance between these two points,

- search for a physical magnitude interval containing the variation in maximum physical magnitude among physical magnitude intervals associated with predetermined distances to refuse the geographic point as a fictitious measurement point when said distance is less than the distance associated with said physical magnitude interval , and - admit the geographic point as a fictitious measurement point when the distance is greater than the distance associated with said interval of physical magnitude; then - by a step of deducing the radio field at each geographical point as a function of the radio fields at the real and fictitious measurement points and of distances between these and the geographical point.

The physical quantity can be the altitude or the radio field.

The variation of physical size around a given geographical point simulates the relief around this point. The nearest measurement point, which can be real or fictitious as the predetermined geographic points are processed, simulates the density of measurement points around the given geographic point. The closer the nearest measurement point is to the geographic point, the more the terrain around the given geographic point is uneven so that the given geographic point is likely to become a fictitious measurement point.

Thus the radio fields initially predicted are only really used, according to the method of the invention, only for the geographical points which are subsequently deemed to be fictitious measurement points, when the physical quantity is not the radio field. The radio field at each geographic point is then deduced, that is to say interpolated, not only as a function of the fields and distances relating to the measurement points on the ground, but also as a function of the fields and distances relative to "fictitious" measurement points according to the invention.

In order not to produce fictitious measurement points having a weak radio field which is no longer high enough for mobile radiotelephones of a radiocommunication network, or for receivers of a radio or television broadcasting network, the step of admitting the geographical point as a fictitious measurement point when the distance is greater than the distance associated with said interval of physical magnitude can include:

- read the real or fictitious type of the nearest measurement point, - predict a transmitter radio field at the geographic point according to characteristics of the transmitter and on the basis of a predetermined propagation model

- admit the geographical point as a fictitious measurement point when the nearest measurement point is an actual measurement point,

- compare the radio fields at the geographical point and at the nearest measuring point with a minimum radio field when the nearest measuring point is a fictitious measuring point, and

- to admit the geographical point as a fictitious measurement point when the radio fields at the geographical point and at the nearest fictitious measurement point are greater than the minimum radio field.

According to another variant, when the physical quantity is the radio field, the step of predicting an emitter radio field at the geographical point can be carried out with the step prior to determining a maximum variation of radio field.

Preferably, the limits of the intervals of physical magnitude, altitude or radio field, consecutive increase when the predetermined distances associated with them decrease in order to improve the efficiency of the method of the invention.

The method of the invention may previously comprise a determination of a step in longitude and a step in latitude between the geographical points where the radio field is predicted. The predetermined radius around the geographical point can be substantially equal to half a step, in order to facilitate the partial implementation of the process in the form of software and reduce the duration of the process.

The method of the invention may previously comprise a selection of the number of radio coverage areas to be viewed and a selection of radio field variation intervals respectively associated with the coverage areas in order to better understand the field variations around the site of the site. 'transmitter.

The processing time for the predetermined geographic points where the radio field is predicted is reduced when the predetermined geographic points are successively and periodically located along a substantially spiral path from the transmitter.

Other characteristics and advantages of the present invention will appear more clearly on reading the following description of several preferred embodiments of the invention with reference to the corresponding appended drawings in which: Figure 1 is a graph on a computer screen, showing three areas of coverage in a processing region around a transmitter;

- Figure 2 is an algorithm of the steps of the method according to the invention; FIG. 3 is a graph schematically illustrating the succession of geographical points of the processing region shown in FIG. 1, to which the method according to the invention is applied; and

- Figure 4 is an algorithm detailing the steps included in the method according to Figure 2 to generate a fictitious measurement point, as a function of variables associated with a current geographic point.

The method for determining radio coverage of a radiofrequency transmitter S according to the invention is mainly implemented in the form of software. The minimum hardware configuration required is an INTEL PENTIUM PC computer running the MICROSOFT WINDOWS NT operating system with 32 MB of RAM memory and a minimum hard drive of 1 GB. The programming language is C ++. The PC computer is configured in a display mode having 256 colors so that the relief effect of a geographic map is viewed.

According to another variant, the hardware is distributed between a server with databases and a user terminal connected by a high speed digital transmission network (INTERNET) and operates with software in JAVA programming language, as described in the aforementioned article by G. BOURLIER et al. and illustrated in Figure 1 of this article. The PC computer also contains geographic data files from a map. For example, the geographic data relate to a map of France comprising the main axes AR and RI of the road network and the hydrographic network and the names of cities, as well as the relief. Each elementary geographic point of the map corresponds to a pixel on the computer screen and is identified by three coordinates X, Y and Z corresponding respectively to the longitude, the latitude and the altitude of the geographic point. The altitude Z of the geographical point is deduced from the two other coordinates X and Y in the plane of the screen shown in FIG. 1, by reading a table stored with two inputs.

The radio coverage determination method according to the invention essentially comprises eleven steps E1 to E12, as shown in FIG. 2.

In the first step E1, a radiofrequency transmitter S whose coverage is to be determined is defined by geographic and technical characteristics. The geographic characteristics of the transmitter are the longitude XS, the latitude YS and the altitude ZS of the site of the transmitter S associated with the name of the transmitter. The technical characteristics of the transmitter S are the frequency of the radio frequency signal emitted by the transmitter, for example the carrier frequency of a television channel, the polarization and the effective radiated power of the signal emitted by the transmitter S, the height of the transmitter antenna above the transmitter site, as well as the azimuth antenna emission diagram. A measurement campaign is carried out in the field in step E1 to measure the radio field of the signal received at various real PMR _j measurement points which are geographically scattered around the transmitter S. The whole index j varies from 1 to a high number J greater than 30 for example. Each real PMR _j measurement point is defined in particular by a longitude XM _j and a latitude YM from which the altitude ZM _j is deduced from the PMR _j point. The PMR _j measurement point is associated with the measurement date and the name of the neighboring municipality, as well as the EM _j radio field value measured at this point, expressed in [dB (μV / m)].

The characteristics of the transmitter S and the characteristics of the measurement points PMR to PMR _j are loaded into the computer PC.

A processing region RT forming a part of the card previously recorded in the computer is determined automatically as a function of the transmission power of the transmitter S and is substantially centered on the transmitter. The processing region RT includes all the actual measurement points PMR _X to PMRj. Alternatively, the user can define the treatment region using the computer mouse and an elastic rectangle movable on the computer screen so that the treatment region completely fills the screen .

By way of example, FIG. 1 shows a rectangular processing region RT in which the site of the transmitter S and the real measurement points PMR _X to PMR _{j are} shown, represented in the form of a square with a cross inside. , on a geographic background of a relief treatment region containing AR road axes in dotted lines and RI rivers in dashed lines. By clicking on a pixel, that is to say by selecting an elementary geographic point of the base map, a first lower status bar BE] _ provides information on the measurement point closest to this pointed geographic point by the mouse such as nearest town, coordinates of the measurement point and radio field of the closest measurement point, and a second status bar BE ₂ provides information on the elementary geographic point pointed by the mouse, such as longitude X, latitude Y and altitude Z of it.

In a second prior step E2, parameters of the coverage area to be determined around the transmitter S in the processing region RT illustrated in FIG. 1 are selected by the user by means of a dialog box. The parameters of the coverage area are, in addition to the aforementioned characteristics of the transmitter S, a minimum threshold for viewing the radio field SEm expressed in [dB (μV / m)] below which the coverage will not be displayed, the number NZ of zones to be displayed for example at most equal to 6, possibly the variation of radio field for each zone expressed in [dB (μV / m) j or else the radio field pitch between two consecutive zones, and the pitch p of I geographic points PG _{j ^} of a digital model grid of the terrain contained in the processing region RT, and optionally a predetermined minimum radio field E _min specific to the invention, with E _min <SEm. The step p defines the horizontal distance in longitude or vertical in latitude between two neighboring geographical points PG _± and PG _{i + 1} where the radio field EG _ir EG _{i + 1} is to be determined. The step p of the geographic points to be processed in the following steps E3 to Eli is greater than or equal to the step of the elementary geographic points.

According to a first example, two coverage areas on the screen of the PC are to be viewed, the first covering radio fields greater than 60 [dB (μV / m)], and the second covering radio fields between E _min = 54 and 60 [dB (μV / m)].

According to a second example illustrated in FIG. 1, NZ = 3 coverage areas Z _x , Z ₂ and Z _NZ = Z ₃ to be displayed on the screen of the PC computer preferably with different colors or shades are selected with a display step of 10 [dB (μV / m)], ie a first zone ∑ι around the transmitter S for radio fields greater than 55 [dB (μV / m)], a second zone Z2 for fields between 45 and 55 [dB (μV / m) j, and a third zone Z3 often far from the transmitter S for fields between E _min = 35 and 45 [dB (μV / m)].

The step p between two neighboring geographic points having the same longitude or the same latitude corresponds for example to 250 m, or to 500 m or 1000 m. The larger the step p, the shorter the time for determining the radio coverage of the transmitter, but also the lower the accuracy.

After the preliminary steps E1 and E2 of loading characteristics of the transmitter S and the measurement points PM ₁ to PM _j and coverage parameters, three steps E3, E4, and E5 are first carried out in this order, or in another order, for each geographic point PG _± of the selected grid constituting a model digital processing region RT around the transmitter S, before deciding in subsequent steps E6 to E10 if the geographic point PGi must constitute a fictitious measurement point PMF according to the invention. The geographic points? G ₁ to PG _j of the selected grid are processed successively from the site of the transmitter S by following a "spiral" path towards the edges of the geographic map base of the processing zone RT, as shown diagrammatically by arrows in figure 3.

Step E3 predicts the radio field EGi at the current geographical point FG _± according to a propagation model previously recorded in the computer PC, as a function of the relief indicated by the base map in a zone substantially between the transmitter S, the operating characteristics are known, and the current geographical point PG. The predicted EG field ^is expressed in [dB (μV / m)]. The propagation model can be determined according to ITU Recommendation 370-5, Geneva.

A maximum variation VGP_ of a predetermined physical quantity GP in a circular area having a predetermined radius typically equal to p / 2 around the point PGi is determined in step E4 to characterize the type of relief around the point PGi.

According to a first embodiment, the predetermined physical quantity GP is the altitude A; the variation VGP _j _ is then an altitude variation maximum VAi, i.e. the difference in altitude between the highest point and the lowest point in the aforementioned circular area. According to a second embodiment, the predetermined physical quantity GP is the radio field E; the variation VGP _j _ is then a maximum electric field variation VE ^, that is to say the difference in radio field predicted between the point which has the best theoretical reception and the point which has the worst theoretical reception in the aforementioned circular area. The radio fields at points in the circular area are predicted according to the propagation model used in step E3.

The next step E5 searches for the measurement point closest to the current geographical point PGi. The type of the nearest measurement point, denoted below PM _if is real if this point is a measurement point PMRi to PMR _j , or is fictitious if this point is a geographical point with an index less than i and selected as a fictitious measurement point PMF during the course of steps E3 to ElO preceding those of the current geographical point PGi. The nearest measurement point PM ^ is associated with a radio field value E i which is loaded in step El if the point PM _A is an actual measurement point, or which is predicted in a previous step E3 if the point PM _i is a fictitious measurement point. The distance Di = Il PG _i , PMjl between the geographical point PGi and the nearest measurement point PMi is calculated.

With reference to FIG. 4, the physical quantities EGi, ^VGP i ^EM i ^{and D} i associated with the current geographic point PGi and stored in steps E3, E4 and E5 are compared respectively with predetermined thresholds to decide whether the geographic point PGi constitutes or does not constitute a fictitious measurement point according to the invention.

In step E6, K intervals of variation of physical quantity, that is to say of altitude or of predicted radioelectric field, consecutive [GP ₀ , GP _j to [GPK- _! , GP _K ] are associated respectively with distances D _x to D _κ . Step E6 searches for one [GP _k , GP _{k +} ^] of the above-mentioned intervals, with 0 <<Kl, in which the variation in maximum physical quantity VGPi ^is understood so that at the next step E7 the distance D _k associated with this interval is compared to the distance Di between the geographical point PGi and the nearest measurement point PM _± . The point PGi is not selected when the distance Di is less than the distance D _k associated with the interval [GP _k , GP _{k + 1} ] at which the maximum variation of physical quantity, altitude or radioelectric field, VGPi ^{= VA} i ^{or VGP} i ^{= VE} i belongs. Knowing that the distances O ₁ to D _κ decrease when the limits GP _Q to GP _K of the intervals of variation of physical magnitude increase, the further the nearest measurement point PMi is from the geographical point PGi, the more the probability that it is selected is high when the variation in maximum VGPi physical quantity ^is low, and conversely, the greater the variation of maximum physical quantity VGP, ^the higher the PMi point can be close geographically PGi so that the latter is selected. The intervals of variation of physical magnitude, altitude or radio field, associated respectively with distances D _k simulate the relief surrounding the geographical point PGi: when the relief is flat, in the plain, few measurement points are necessary, while a point density of Fictitious and / or real measurements are necessary when the terrain is uneven, such as in the mountains.

For the first realization with altitude A as physical quantity GP, for example K = 6 altitude variation intervals are selected

[A ₀ , Ai] = [0 m, 10 m] with D _x = 20,000 m,

[A ₂ , A ₂ ] = [10 m, 50 m] with D ₂ = 12000 m,

[A ₂ , A ₃ ] = [50 m, 100 m] with D ₃ = 7000 m, [A ₃ , A ₄ ] = [100 m, 200 m] with D ₄ = 4000 m,

[A ₄ , A ₅ ] = [200 m, 400 m] with D ₅ = 3000 m, and [A ₅ , A ₆ ] = [400 m, 800 m] with D ₆ = 2000 m. According to this example, if VAi = 42 m, and if D _i = 6450 m <D ₂ , the geographical point PGi is not selected as a fictitious measurement point: step E7 is continued by step E3 if the index i is less than I, after incrementing by a unit of the index i, to carry out steps E3 to ElO for the following geographical point PG _{i + 1} . On the other hand if D _i is equal for example to 18100 m> D ₂ , the process proceeds to the next step E8.

For the second embodiment with the radio field E as the physical quantity GP, for example K = 4 intervals of variation of the radio field are selected:

[E ₀ , E _T. ] = [0 dB (μV / m), 2 dB (μV / m)] with D _λ = 20000 m, [E _lf E ₂ ] = [2 dB (μV / m), 5 dB (μV / m)] with D ₂ = 10,000 m, [E ₂ , E ₃ ] = [5 dB (μV / m), 12 dB (μV / m)] with D ₃ = 5,000 m, [E ₃ , E ₄ ] = [12 dB (μV / m), 30 dB (μV / m)] with D ₄ = 2000 m, According to this example, if VE _± = 4 dB (μV / m), and if D = 6450 m <D ₂ , the geographic point PGi is not selected as a fictitious measurement point: step E7 is continued by step E3 if the index i is less than I, after incrementing by one unit of the index i, to carry out steps E3 to ElO for the following geographic point PG _{i + 1} . On the other hand if D _A is equal for example to 10500 m> D ₂ , the process proceeds to the next step E8.

When the variation of maximum physical quantity VGPi, ^VA i ^{or VE} i ^and ^ ^at distance D _x for the geographical point PGi satisfy the conditions of steps E6 and E7, the type, real or fictitious, of the nearest measuring point PMi is read in step E8. If the measurement point PMi is an actual measurement point, that is to say having been defined during the previous measurement campaign, the geographic point PG-_ is deemed to be a fictitious measurement point PMF according to the invention at l step E10, and the method returns to step E3 for the next geographic point PG _{i + 1} if the index i is less than I at step Eli.

When in step E8 the measurement point PM _X is a fictitious measurement point, the current geographical point PGi is deemed to be a fictitious measurement point in step ElO if at the same time, in step E9, the radio field predicts EGi ^{at the} geographic P ° PG is greater than the predetermined minimum radio field E _min and the radio field EM _X at the nearest measurement point P i is greater than the minimum radio field E _min . Otherwise, when the radio field EGi or EM _i is less than E _min , the geographical point PGi is not a fictitious measurement point, and the method returns to step E3 after incrementing the index i.

Then after the step E10, the method is looped back, as already said, if the index i is less than the number I of geographical points of the grid of digital terrain model, so as to increment the index i by one and performing steps E3 to Eli for each subsequent geographic point of the grid in the processing region RT scanned according to the spiral shown in FIG. 3. Each geographic point deemed to be a fictitious measurement point PMF thus presents a predicted radio field which can be greater than the minimum radio field ^E min when the nearest measurement point PM _i is fictitious, or which can be less or greater than E _min when the point PMi is real.

Thus, for an interval [GP _k , GP _{k + 1} ] containing VGPi, any geographic point PGi with EGi ^{> E} min ^is selected as the fictitious PMF measurement point when Di is greater than D _k , with the exception of the case where the nearest measuring point PM _± is a fictitious point and the field EMi of the nearest measuring point where the predicted field EGi ^is already less than the predetermined minimum radio field E _min . This means that the point considered PGi is already too far from the coverage area and that it is useless to select it, which limits the number of fictitious measurement points generated and reduces the time taken for the process to proceed.

As a variant, when the physical quantity GP is different from the predicted radio field E, that is to say is the altitude A, step E3 for predicting the radio field at the geographical point PG _± shown in FIG. 2 is deleted and replaced by a step E3 'identical to step E3 and introduced between steps E8 and E9 when the point PM _i is fictitious, and between steps E8 and ElO when the point PMi is real, as shown in dotted lines in the Figure 4. The fields are predicted only for the geographic points PGi having satisfied the condition Di> D _k in the previous step E7. Whether the nearest measurement point PMi is of a fictitious type or of a real type in step E8, the prediction of the EGi field ^is nevertheless performed since the next step E12 needs the predicted fields of all the fictitious measurement points.

This variant reduces the duration of steps E3 to E10 and therefore the duration of the process.

When the physical quantity GP is equal to the radioelectric field E, step E3 ′ does not exist and step E3 is maintained since in step E4, the radioelectric field is necessarily predicted at the geographical point EG _j _ and at surrounding points.

Referring to FIG. 2, after steps E3 to Eli have been carried out for each geographic point PGi to PGj of the grid in the processing region RT, step E12 follows an interpolation algorithm based on the points of real PMR _X to PMRj measurements and the fictitious PMF measurement points generated in the previous step ElO according to the invention, designated indifferently by PM _m below.

Interpolation consists in defining a function

2 s from R to R which satisfies the conditions (s (XM _m ,

YM _m ) = E _m ; with 1 <m <M}. XM _m and YM _m represent the coordinates of the measurement point PM _m , E _m the value of the radio field associated with the measurement point PM _m , and M the number of real and fictitious measurement points.

The function s is of the form m = M s (PGi) = ∑ ^ 0 (11 PGi - PMJI), m = \ where PGi is a geographic point of the treatment region, 0 is a dependent "radial" type function of the Euclidean distance (Il PGi - PM _m | I) between the points PG ^ and PM _m , and μ ^ represents a weighting as a function of the measurement point PM _m ; the real measurement points PMR} to PMRj have a weight for example 10 times greater than that of the fictitious measurement points PMF.

Interpolation by radial function and the type of algorithm treated are described in the article "RADIAL BASIS FUNCTIONS FOR MULTIVARIABLE INTERPOLATION: A REVIEW" by M.J.D. POWELL, pages 143 to 167, in the book "Algorithms for Approximation", edited by Mason & Cox, Clarendon Press Oxford, 1987. The interpolation function "passes" by the real measurement points, "passes" almost by the fictitious measurement points and is calculated on the other geographical points according to the distances which exist with the measurement points and the radio field values which are associated with them.

In practice, several measurement campaigns can supplement initial determinations of radio coverage of a given transmitter in order to refine the radio coverage.

Claims

1 - Method for determining the radio coverage of a transmitter (S) on a geographic map (RT), comprising measurements (El) of radio field (EM _j ) emitted by the transmitter at real measurement points (PMR _j ), characterized by the following steps for each geographic point

⁽ PGi ⁾ : - determine (E4) a maximum variation (VGP _j _) of a physical quantity (GP) within a predetermined radius around the geographical point (PGi),

- search (E5) for a measurement point (PM) closest to the geographical point (PGi) and assess the distance (Di) between these two points (PMi, PGi),

- search (E6, E7) for an interval of physical magnitude containing the variation in maximum physical magnitude (VGPi) among intervals of physical magnitude (GP _k , GP _{k + 1} ) associated with predetermined distances (D _k ) to refuse the point geographic (PGi) as a fictitious measurement point when said distance (Di) is less than the distance associated with said interval of physical magnitude, and - admit (E8, ElO) the geographic point (PG _i ) as a fictitious measurement point (PMF ) when the distance (Di) is greater than the distance associated with said interval of physical magnitude; then

- by a step of deducing (E12) the radio field at each geographical point (PG _i ) as a function of the radio fields at the real and fictitious measurement points (PMR _j , PMF) and of distances between these and the geographical point. 2 - Process according to claim 1, according to which the physical quantity (GP) is the altitude (A).

3 - Process according to claim 1, according to which the physical quantity (GP) is the radioelectric field (E).

4 - Process according to any one of claims 1 to 4, according to which the step of admitting the geographical point as a fictitious measurement point comprises

- read (E8) the real or fictitious type of the nearest measurement point (PMi), predict (E3 ') a radio field of the transmitter (EGi) ^at the geographical point (PG _i ) according to the characteristics of the transmitter (S) and on the basis of a predetermined propagation model,

- admit (ElO) the geographic point (PGi) as a fictitious measurement point (PMF) when the closest measurement point (P i) is an actual measurement point, compare (E9) the radio fields

(EGi, ^EM i) ^at the geographic point (PGi) and at the nearest measurement point (PMi) at a minimum radio field (E _min ) when the closest measurement point (PM) is a fictitious measurement point,

- admit (ElO) the geographical point (PG _i ) as a fictitious measurement point (PMF) when the radio fields (EG, ^EM i) ^at the geographical point (PG) and at the nearest fictitious measurement point (PMi) are greater at the minimum radio field (E _m i _n ). 5 - Method according to claim 4, when it depends on claim 3, according to which the step (E3) of predicting a radio field of the transmitter (EG at the geographical point (PG _j _) is carried out with the step (E4) to determine a maximum variation of radio field (VE ^).

6 - Process according to any one of claims 1 to 5, according to which the limits of the consecutive physical magnitude intervals (GP _k , GP _{k + 1} ) increase when the predetermined distances (D _k ) which are associated with them decrease.

7 - Method according to any one of claims 1 to 6, comprising beforehand (E2) a determination of a step (p) in longitude (X) and a step (p) latitude (Y) between the geographical points (PGi) where the radio field is predicted.

8 - Process according to claim 7, according to which the predetermined radius around the geographical point (PGi) is substantially equal to the half-step (p / 2).

9 - Method according to any one of claims l to 8, comprising beforehand a selection (E2) of the number (NZ) of radio coverage areas (Z ₁ to Z _NZ ) to be displayed and a selection of intervals of variation of radio field respectively associated with the coverage areas. 10 - Process according to any one of claims 1 to 9, according to which the geographical points (PG to PG _X ) where the radio field is predicted are successively and periodically located along a path substantially in spiral from the transmitter (S).