FR3126164A1 - METHOD FOR AIDING THE DETERMINATION OF A GEOGRAPHICAL LOCATION FOR THE IMPLEMENTATION OF HERTZ BROADCASTING EQUIPMENT - Google Patents

Abstract

The invention relates to a method for assisting in the determination of geographical locations for the siting of television broadcasting equipment, the method comprising the following phases: Obtaining (100) a bare terrain profile along at least a line of sight (LOS) between first and second desired locations for the installation of television broadcasting equipment, Determination (200) of a georeferenced digital surface model, Generation (300) of a three-dimensional elevation model representing each line of sight, overground elements arranged along each line of sight, and the bare ground along each line of sight, notable in that the phase of determining a digital surface model comprises the following steps: Obtaining (210) a plurality of aerial images representative of geographical areas located between the first and second desired locations,Estimating (220) the topography of the objects represented in the plurality of aerial images to get the surface model. Figure to be published with abstract: Fig. 3

Description

METHOD FOR AIDING THE DETERMINATION OF A GEOGRAPHICAL LOCATION FOR THE IMPLEMENTATION OF HERTZ BROADCASTING EQUIPMENT

FIELD OF THE INVENTION

The present invention relates to the technical field of radio broadcasting equipment.

Such equipment is deployed in the field for remote transmissions, in particular at the level of telecommunications such as antennas intended for the GSM system (abbreviation of the Anglo-Saxon expression "Global System for Mobile Communications" ) and PCS (abbreviation of the Anglo-Saxon expression -Saxon “Personal Communications Services” ), and more generally to hertzian telephony relays.

More specifically, the invention relates to the implementation of a wireless network infrastructure, and in particular to a method for helping to determine the geographical locations of sites intended for television broadcasting.

BACKGROUND OF THE INVENTION

1. General principle

Mobile telephone networks are made up of sites (generally installed on high points: pylons, roofs of buildings, water towers, radio towers, etc.) on which antennas are installed responsible for establishing communication with telephones. surrounding mobiles.

Each site must have a transmission solution allowing it to connect to the telecommunications network. More specifically, each site must have a data transmission solution to another site in the telecommunications network.

Different transmission solutions exist, whether wired or wireless. Among these solutions, one of them consists in establishing a radio beam transmission between first and second sites. To do this, first and second antennas (dishes) are installed respectively on the first and second sites to communicate, and each antenna is pointed in the direction of its counterpart. A concentrated beam of radio frequency waves emitted by the first antenna can then be received by the second antenna.

Microwave transmission offers the advantage of rapid implementation and relatively light in terms of infrastructure (unlike other solutions, such as fiber optics). However, for the quality of radio beam transmission to be sufficient, it is necessary to ensure that no obstacle intersects a wave propagation path of the radio frequency wave beam.

Indeed, natural obstacles (tree, mountain, etc.) or artificial (building, metal structure, etc.) located along the path of propagation of the wave beam can cause the reflection of a part (or the totality ) of the wave beam propagating between the first and second antennas. This induces a decrease in the signal level received by the second antenna.

Furthermore, in the event of multiple reflections, the reflected part of the wave beam may reach the second antenna at the same time as a direct wave beam emitted by the first antenna, which may disturb the signal received by the second antenna. .

This is why prior to setting up a new site intended for television broadcasting, it is necessary to check that a clear propagation path (i.e. without obstacles) exists between this new site and at least one other site of the telecommunication.

Most of the energy of the wave beam (and therefore most of the bandwidth) is concentrated in this propagation path CP which has the shape of a "spindle" , as illustrated in .

• une ligne de visée LOS, et
• une première zone de Fresnel (dénommé« 1er ellipsoïde de Fresnel »).

The propagation path CP between two sites is defined by:

• a LOS line of sight, and
• a first Fresnel zone (called “1st Fresnel ellipsoid” ).

The line of sight LOS corresponds to the straight line passing through the first and second antennas A1, A2.

• centrés sur la ligne de visée LOS,
• perpendiculaires à la ligne de visée LOS au niveau d’un point respectif,
• situés entre les première et deuxième antennes A1, A2, le rayon de chaque cercle dépendant de la position de son centre le long de la ligne de visée LOS.

The Fresnel zone corresponds to the sum of the areas of a set of circles:

• centered on the LOS line of sight,
• perpendicular to the LOS line of sight at a respective point,
• located between the first and second antennas A1, A2, the radius of each circle depending on the position of its center along the line of sight LOS.

With reference to the , an example of a propagation path CP has been illustrated between first and second antennas A1, A2 of sites intended for television broadcasting. The first Fresnel zone corresponds to the set of points P such that: d1+d2 = D + Lambda/2,

• d1 : la distance entre la première antenne et un point P donné,
• d2 : la distance entre la deuxième antenne et le point P donné,
• D : la distance entre les première et deuxième antennes,
• Lambda : la longueur d’onde du faisceau d’ondes radiofréquences.

With :

• d1: the distance between the first antenna and a given point P,
• d2: the distance between the second antenna and the given point P,
• D: the distance between the first and second antennas,
• Lambda: the wavelength of the radio frequency wave beam.

2. Existing solutions

Various methods for assisting in the determination of geographical locations of sites intended for television broadcasting have been proposed.

• détermination, à partir de données topographiques mises à disposition par divers organismes (IGN, NASA, etc.), d’un profil de terrain nu entre des premier et deuxième emplacements désirés pour des première et deuxième antennes,
• identification, à partir d’images aériennes, d’éléments de sursol (bâtiment, arbre, structure métallique, etc.) entre les premier et deuxième emplacements désirés, et attribution à chaque élément d’une hauteur arbitraire,
• obtention d’un modèle théorique dans lequel la ligne de visée, et les éléments de sursol entre les premier et deuxième emplacements désirés sont intégrés sur le profil de terrain nu,
• détection des éléments de sursol potentiellement gênants dans le modèle théorique, c’est-à-dire des éléments de sursol susceptibles d’intersecter le chemin de propagation CP (i.e. pénétrant dans l’ellipsoïde de Fresnel, ou obstruant la ligne de visée LOS).

These different processes include a theoretical phase including the following steps:

• determination, from topographic data made available by various organizations (IGN, NASA, etc.), of a bare terrain profile between first and second locations desired for first and second antennas,
• identification, from aerial images, of overground elements (building, tree, metal structure, etc.) between the first and second desired locations, and attribution to each element of an arbitrary height,
• obtaining a theoretical model in which the line of sight, and the overground elements between the first and second desired locations are integrated on the bare terrain profile,
• detection of potentially disturbing overground elements in the theoretical model, i.e. overground elements liable to intersect the propagation path CP (ie penetrating the Fresnel ellipsoid, or obstructing the line of sight LOS) .

By way of illustration, an example of a theoretical model including a bare terrain profile PTn, overground elements ES1-ES4, and a line of sight LOS is shown in . The bare terrain profile is a three-dimensional digital representation of the topography of a given region that does not take into account the objects (vegetation, buildings, lakes, etc.) implanted on the ground. The bare terrain profile is representative of the altitude of the bare ground (we speak of “DTM” , acronym for the expression “Digital Terrain Model”). Aboveground elements correspond to all the objects located on the ground, such as natural elements (vegetation, lake, river, etc.) and artificial elements (buildings, metallic structures, etc.).

• vérification par un opérateur de la ligne de visée en mettant en œuvre une visée photographique depuis l’emplacement désiré pour chacune des première et deuxième antennes,
• vérification du dégagement entre le chemin de propagation CP et les éléments de sursol identifiés comme potentiellement gênants,
• mise à jour du modèle théorique à partir des mesures réalisées sur le terrain.

The theoretical phase must then be verified and consolidated during a practical phase including the following steps:

• verification by an operator of the line of sight by implementing photographic sighting from the desired location for each of the first and second antennas,
• verification of the clearance between the CP propagation path and the above ground elements identified as potentially troublesome,
• updating of the theoretical model based on measurements taken in the field.

The photographic aiming can be carried out by one (or more) operator(s) who climb(s) each pylon intended to receive a respective antenna among the first and second antenna, or who use(s) any other means allowing him (them) to reach the desired location for each of the first and second antennas to be installed (for example by using drones equipped with cameras).

By validating that: the second antenna is visible from the first antenna by photographic sighting, and that the first antenna is visible from the second antenna by photographic sighting, the operator demonstrates that the line of sight is not obstructed by the one of the potentially troublesome above-ground elements identified in the theoretical model.

• un dégagement positif indique que l’élément de sursol demeure hors de la première zone de Fresnel,
• un dégagement négatif indique que l’élément de sursol pénètre dans la première zone de Fresnel (voire obstrue la ligne de visée) et constitue un obstacle.

The clearance verification step consists of the operator measuring the actual height of each above-ground element identified as potentially troublesome in the theoretical model. This measurement can be carried out using a device of the laser rangefinder type. The clearance is representative of a distance between each overground element and the propagation path CP:

• a positive clearance indicates that the overground element remains outside the first Fresnel zone,
• a negative clearance indicates that the overground element enters the first Fresnel zone (or even obstructs the line of sight) and constitutes an obstacle.

The update step consists of replacing, in the theoretical model, the arbitrary heights assigned to the elements identified as potentially troublesome by their actual heights measured during the practical phase.

The actual measured heights of the potentially troublesome overfloor elements are then taken into account to calculate the actual clearance between these overfloor elements and the first Fresnel zone.

The comparison of these clearance values with acceptability thresholds (determined by the sponsor of the study) makes it possible to conclude on the feasibility or not of the microwave link between the geographical locations of the two sites intended for television broadcasting.

3. Problems associated with existing solutions and purpose of the invention

The implementation of such a method has many drawbacks.

In particular, this implementation requires a trip to the field to verify and consolidate the theoretical model. This is time and resource consuming, which increases the cost associated with this implementation.

• l’élément de sursol considéré peut être inaccessible à l’opérateur chargé de mesurer sa hauteur (accès à des propriétés privées, terrain accidenté),
• la reconnaissance sur le terrain de l’élément de sursol identifié comme potentiellement gênant dans le modèle théorique peut être difficile ou impossible (cas des zones étendues d’obstacles, telles que les forêts),
• la réalisation de la mesure de la hauteur d’un élément de sursol considéré peut être difficile ou impossible (par exemple lorsque l’opérateur ne peut pas prendre le recul nécessaire pour mesurer la hauteur de l’élément de sursol considéré, ou lorsque le sommet de l’élément de sursol considéré ne peut pas être atteint par l’instrument de mesure, etc.),
• l’étendue et le nombre d’éléments de sursol à mesurer peuvent dépasser la capacité de réalisation sur le terrain (cas des zones forestières étendues, où la mesure des arbres sur la ligne de visée peut représenter des longueurs significatives).

In addition, measuring the height of certain floor elements identified as potentially troublesome can be difficult, if not impossible, to perform:

• the aboveground element considered may be inaccessible to the operator responsible for measuring its height (access to private properties, uneven ground),
• recognition in the field of the aboveground element identified as potentially troublesome in the theoretical model may be difficult or impossible (case of large areas of obstacles, such as forests),
• measuring the height of an above-ground element in question may be difficult or impossible (for example when the operator cannot take the necessary distance to measure the height of the above-ground element in question, or when the top of the considered above ground element cannot be reached by the measuring instrument, etc.),
• the extent and the number of aboveground elements to be measured may exceed the ability to achieve on the ground (case of extensive forest areas, where the measurement of trees on the line of sight may represent significant lengths).

An object of the present invention is to propose a method for assisting in the determination of geographical locations of sites intended for television broadcasting, making it possible to overcome at least one of the aforementioned drawbacks.

BRIEF DESCRIPTION OF THE INVENTION

• Obtention d’un profil de terrain nu le long d’au moins une ligne de visée entre des premier et deuxième emplacements désirés pour l’implantation d’équipements de télédiffusion,
• Détermination d’un modèle numérique de surface géoréférencé,
• Génération d’un modèle tridimensionnel d’altitude représentant chaque ligne de visée, des éléments de sursol disposés le long de chaque ligne de visée, et le sol nu le long de chaque ligne de visée,
• remarquable en ce que la phase de détermination d’un modèle numérique de surface comprend les étapes suivantes :
  • Obtention d’une pluralité d’images aériennes représentatives de zones géographiques situées entre les premier et deuxième emplacements désirés,
  • Estimation de la topographie des objets représentés dans la pluralité d’images aériennes pour obtenir le modèle de surface.

To this end, the invention proposes a method for assisting in the determination of geographical locations for the installation of television broadcasting equipment, the method comprising the following phases:

• Obtaining a bare terrain profile along at least one line of sight between first and second desired locations for the installation of broadcasting equipment,
• Determination of a georeferenced digital surface model,
• Generation of a three-dimensional elevation model representing each line of sight, overground elements arranged along each line of sight, and bare ground along each line of sight,
• remarkable in that the phase of determining a digital surface model includes the following steps:
  • Obtaining a plurality of aerial images representative of geographical areas located between the first and second desired locations,
  • Estimation of the topography of the objects represented in the plurality of aerial images to obtain the surface model.

Thus, the method according to the invention makes it possible to obtain a three-dimensional model of the relief and of the overground elements between two desired locations for the installation of antennas that do not require a practical phase of measurement on the ground of the height of above ground elements.

• la phase d’obtention d’un profil de terrain nu peut comprendre :
  • la saisie de coordonnées de premier et deuxième points extrêmes correspondant respectivement aux premier et deuxième emplacements désirés pour l’implantation d’équipements de télédiffusion,
  • l’extraction d’une base de données géographique d’un nuage de points représentatifs de l’altitude du sol entre les premier et deuxième points extrêmes ;
• l’étape de génération d’un modèle tridimensionnel peut comprendre une étape de sélection des points du modèle numérique de surface représentatif d’un élément de sursol ;
• l’étape de sélection peut comprendre les sous-étapes consistant à :
  • comparer l’altitude de chaque point du modèle de terrain nu à l’altitude de son homologue radiométrique dans le modèle numérique de surface,
  • si la différence entre lesdites altitudes est inférieure à une valeur seuil, alors attribuer l’altitude du point du profil de terrain nu au point correspondant dans le modèle tridimensionnel,
  • si la différence entre lesdites altitudes est supérieure ou égale à la valeur seuil, alors attribuer l’altitude du point du modèle numérique de surface au point correspondant dans le modèle tridimensionnel ;
• l’étape d’estimation de la topographie des objets représentés dans la pluralité d’images aériennes peut être réalisée par photogrammétrie ;
• la phase de génération d’un modèle tridimensionnel peut comprendre en outre les étapes suivantes :
  • réalisation d’une coupe verticale du modèle numérique de surface selon la ligne de visée (LOS),
  • réalisation d’une coupe verticale du profil de terrain nu selon la ligne de visée (LOS),
  • superposition des éléments de sursol de la coupe verticale du modèle numérique de surface sur la coupe verticale du profil de terrain nu ;
• le procédé peut également comprendre une phase de détection d’éléments de sursol potentiellement gênants dans le modèle tridimensionnel, ladite phase de détection comprenant les étapes suivantes :
  • calculer une première zone de Fresnel le long de la ligne de visée
  • comparer la hauteur de chaque élément de sursol à l’altitude de la première zone de Fresnel le long de la ligne de visée entre les premier et deuxième points extrêmes ;
• la rotondité de la terre peut être prise en compte lors de la mise en œuvre de la phase de détection ;
• les indices de réfraction des couches atmosphériques situées entre les premier et deuxième points extrêmes peuvent être pris en compte lors de la mise en œuvre de la phase de détection.

Preferred but non-limiting aspects of the implantable device according to the invention are the following:

• the phase of obtaining a bare ground profile may include:
  • the entry of coordinates of first and second extreme points corresponding respectively to the first and second locations desired for the installation of television broadcasting equipment,
  • the extraction from a geographical database of a cloud of points representative of the altitude of the ground between the first and second extreme points;
• the step of generating a three-dimensional model can comprise a step of selecting the points of the digital surface model representative of a supersoil element;
• the selection step may include the sub-steps of:
  • compare the elevation of each point in the bare terrain model to the elevation of its radiometric counterpart in the digital surface model,
  • if the difference between said altitudes is less than a threshold value, then assigning the altitude of the point of the bare terrain profile to the corresponding point in the three-dimensional model,
  • if the difference between said altitudes is greater than or equal to the threshold value, then assigning the altitude of the point of the digital surface model to the corresponding point in the three-dimensional model;
• the step of estimating the topography of the objects represented in the plurality of aerial images can be carried out by photogrammetry;
• the generation phase of a three-dimensional model may also include the following steps:
  • production of a vertical section of the digital surface model along the line of sight (LOS),
  • production of a vertical section of the bare terrain profile along the line of sight (LOS),
  • superposition of the overground elements of the vertical section of the digital surface model on the vertical section of the bare terrain profile;
• the method can also comprise a phase for detecting potentially troublesome surface elements in the three-dimensional model, said detection phase comprising the following steps:
  • calculate a first Fresnel zone along the line of sight
  • comparing the height of each overground element to the altitude of the first Fresnel zone along the line of sight between the first and second extreme points;
• the roundness of the earth can be taken into account when implementing the detection phase;
• the refractive indices of the atmospheric layers located between the first and second extreme points can be taken into account during the implementation of the detection phase.

The invention also relates to a system for assisting in the determination of geographical locations of sites intended for television broadcasting comprising means for implementing the aforementioned method.

Other characteristics and advantages of the invention will emerge better from the following description of several variant embodiments, given by way of non-limiting examples, from the appended drawings in which:

is a schematic representation of two sites intended for television broadcasting,

is a schematic representation of a theoretical model including a bare terrain profile, overground elements and a line of sight,

is a schematic representation of the steps of the method for helping to determine the geographical locations of sites intended for television broadcasting,

is a schematic representation illustrating the roundness of the earth,

is a schematic representation illustrating a deformation of a line of sight as a function of the refraction of atmospheric layers traversed.

Claims (10)

Method for assisting in the determination of geographical locations for the installation of television broadcasting equipment, the method comprising the following phases:

• Obtaining (100) a bare terrain profile along at least one line of sight (LOS) between first and second desired locations for the installation of television broadcasting equipment,
• Determination (200) of a georeferenced digital surface model,
• Generating (300) a three-dimensional elevation model representing each line of sight, overground elements disposed along each line of sight, and bare ground along each line of sight,
• Detection of disturbing ground elements in the three-dimensional model,

characterized in that the phase of determining a digital surface model includes the following steps:

• Obtaining (210) a plurality of aerial images representative of geographical areas located between the first and second desired locations,
• Estimating (220) the topography of the objects represented in the plurality of aerial images to obtain the surface model.

Method according to claim 1, in which the phase of obtaining a bare ground profile includes:

• the entry of coordinates of first and second extreme points corresponding respectively to the first and second locations desired for the installation of television broadcasting equipment,
• extracting from a geographical database a cloud of points representative of the altitude of the ground between the first and second extreme points.

Method according to any one of Claims 1 or 2, in which the step of generating a three-dimensional model comprises a step of selecting the points of the digital surface model representative of an overground element. Method according to claim 3, in which the selection step includes the sub-steps of:

• compare the elevation of each point in the bare terrain model to the elevation of its radiometric counterpart in the digital surface model,
• if the difference between said altitudes is less than a threshold value, then assigning the altitude of the point of the bare terrain profile to the corresponding point in the three-dimensional model,
• if the difference between said altitudes is greater than or equal to the threshold value, then assigning the altitude of the point of the digital surface model to the corresponding point in the three-dimensional model.

A method according to any of claims 1 to 3, wherein the step of estimating the topography of objects depicted in the plurality of aerial images is performed by photogrammetry. Method according to any one of the preceding claims, in which the generation phase of a three-dimensional model also includes the following steps:

• production of a vertical section of the digital surface model along the line of sight (LOS),
• production of a vertical section of the bare terrain profile along the line of sight (LOS),
• superposition of the overground elements of the vertical section of the digital surface model on the vertical section of the bare terrain profile.

Method according to any one of the preceding claims, In which the phase of detecting disturbing subsoil elements in the three-dimensional model includes the following steps:

• calculate a first Fresnel zone along the line of sight
• comparing the height of each overground element to the elevation of the first Fresnel zone along the line of sight between the first and second extreme points.

Method according to claim 7, in which the roundness of the earth is taken into account when carrying out the detection phase. Method according to any one of Claims 7 or 8, in which the refractive indices of the atmospheric layers located between the first and second extreme points are taken into account during the implementation of the detection phase. System for assisting in the determination of geographical locations of sites intended for television broadcasting comprising means for implementing the method according to any one of Claims 1 to 9.