FR3099570A1 - OPTICAL REFLECTION DEVICE FOR THE SURVEY OF NON VISIBLE POINTS - Google Patents

Abstract

The subject of the invention is an optical reflection device (1). The invention is characterized in that the device comprises: - a mirror (2) with a strictly flat surface, having at least one reflective layer on the first surface with a reflection rate of at least 90% in the visible range and infrared and a center of symmetry; - a mirror frame (3); - a fork (4) which encloses said mirror frame (3) and allows said mirror (2) to be pivoted about a horizontal and vertical axis; and - a vertical support (5), fixed in said fork (4) and lying directly above the center of symmetry of said first reflecting surface of said mirror (2). The subject of the invention is also the use of the device according to the invention for determining the planimetric and altimetric coordinates of a target point A (XA, YA, ZA) from a total station S hence A n 'is not visible by direct sighting and reading from the total station S as well as different methods for determining planimetric and altimetric coordinates of a target point A hidden using a device according to the invention. Figure 1

Description

OPTICAL REFLECTION DEVICE FOR SURVEYING NON-VISIBLE POINTS

The present invention relates to an optical reflection device useful in topography, making it possible to survey a point by means of a total station, said point not being visible by sighting and direct reading from the total station, as well as different methods applicable in the field to determine the coordinates of a hidden target point using the device according to the invention.

In topography, a survey (or survey) aims to collect existing data on the ground with a view to their transcription, to scale, on a plan or on a map.

The measuring device in topography has since evolved over time: one of the first devices designed is called theodolite and only measures horizontal H and vertical V angles, the distance being measured at the chain. Then, a tacheometer was developed: it is a theodolite including an integrated rangefinder. Then, we developed a total station which is a total station equipped with a memory card to store the data. Today, there are also robotic total stations, which can locate prisms and track them in real time but only in direct sight. If the operator holding the prism moves, the station follows him by rotating.

A total station is a device frequently used in topography in all ground surveying operations (topographic surveying), in various types of work in the fields of construction and industry (in particular aeronautics) as well as in archeology ( survey of objects in 3 absolute coordinates). It allows the measurements taken in the field to be stored in a memory card, to be transferred and then processed by computer (in proprietary DXF, DWG or other format), using computer-aided design (CAD) programs or spreadsheets. .

Two joint operations are necessary to be able to locate each point along three axes X, Y (plane) and Z (altitude): the planimetric survey and the altimetric survey.

The horizontal and vertical angles between two targets, as well as the distance between these targets are measured by two graduated circles and a rangefinder integrated into the total station. The measurements taken make it possible to transfer the terrain in X, Y to a plan or map. The altitude Z is represented by level curves.

The measurement of distances is done using an infrared or laser sighting rangefinder integrated in the total station. The measurement can be made using a tetrahedral reflector prism, placed vertically to the point to be measured using a spherical spirit level. For this purpose, in practice, aiming at any point is understood to mean aiming not at the point on the ground whose coordinates one seeks to determine, but commonly at the reflector prism located vertically thereto at a certain height h. A ray is sent to the prism. The ray is reflected in the direction from which it came (catoptric property of the prism). We then measure the round trip time of the ray, ie Δt. We deduce the distance between the viewfinder and the prism from the following formula: d = ½ * c * Δt, with c representing the constant of the speed of light. However, corrections still need to be made to the distances in topography by taking into consideration the prism constant (manufacturer data), the atmospheric correction or even the refractive index of the propagation medium n (= C ₀ /C with C = speed of the wave in the medium and C ₀ = speed of the wave in vacuum) whose current value is of the order of 1.000290. The use of an integrated laser rangefinder also makes it possible to carry out a distance measurement by laser ranging, without using a prism, which makes it possible to use as a target visible places that are difficult to reach.

Also, it is first necessary to put the total station in station, that is to say that it must be positioned so that its vertical axis is perpendicular to the horizontal plane in which the total station is positioned. It is then possible to survey all the characteristic points of the terrain.

From this station point, it will be possible to carry out a series of distance measurements by radiation, for example by emission of a laser or infrared beam.

Also, if the terrain is very extensive, it will be necessary to make a path. It will then be necessary to move the measuring device to be able to cover the entire field of the study.

The polygonal or polygonal traverse consists of moving the station point. It will be necessary to note, from the point of station 1, the position of the station 2 to know the coordinates of this one and so that the identification is complete, it is not necessary to forget to note on the station 2 the position of the station 1 (so that the points surveyed from station 2 are identified in the same measurement system with respect to station 1). The successive station points (station 1, station 2, station 3, etc.) are thus linked to each other.

The initial station setting must often be supported by two or three stations from which the measuring instrument will target the same points to confirm their coordinates by triangulation.

However, it is relatively restrictive in terms of handling and the time required to move and set up a total station again to complete the survey of points that could not be surveyed from the previous stations.

In addition, to survey a point, it is essential that it be visible by sighting and direct reading from the total station, i.e. it must not be hidden from the station. total by the slightest obstacle.

Several manufacturers of topographic equipment have studied the possibilities of allowing the survey of hidden points.

The document FR3013116 describes a device which makes it possible to tilt the prism-holder rods to survey the hidden points during total station surveys. The device attaches to all rods, whatever their diameter. The tilter consists of an angle iron which supports two tiltmeters and three viewfinders. The edge of the angle iron is obviously parallel to the axis of the rod. The 3 sights are fixed on side A of the angle iron. The inclinometers, fixed, one on face A, the other on face B of the angle iron, provide the inclination of the rod in two directions perpendicular to each other and perpendicular to the rod. These two single-axis inclinometers can be replaced by a two-axis inclinometer fixed on side B of the angle iron.

However, such a solution allowing the prism-holder rods to be tilted does not make it possible to survey hidden points, obstructed by a substantial obstacle or located in a cavity, not visible from the total station.

In practice, construction sites often include substantial obstacles such as buildings already present or under construction, or machinery. To determine the coordinates of points not visible from the total station, it is then necessary to create a new polygonal to have covisibility.

This method has two drawbacks. On the one hand, moving topographic equipment and setting it up takes time. On the other hand, the surveys carried out during the same campaign will be carried out under different conditions, with a different measure of inaccuracy depending on the location of the total station, which will affect the overall reliability of the surveys.

Technical problem

Considering the above, a problem that the present invention proposes to solve consists in developing an optical reflection device allowing the survey of a hidden point not visible directly from the total station without causing displacement of the total station.

Technical solution

The solution to this problem has as its first object an optical reflection device, characterized in that it comprises:
- A mirror with a strictly flat surface, having at least one reflective layer on the first surface with a reflection rate of at least 90% in the visible and infrared range and a center of symmetry;
- a mirror frame;
- A fork which encloses said mirror frame and makes it possible to pivot said mirror around a horizontal and vertical axis; And
- A vertical support, fixed in said fork and located directly above the center of symmetry of said first reflecting surface of said mirror.

Its second object is the use of the optical reflection device according to the invention for determining planimetric and altimetric coordinates of a target point A (X _A , Y _A , Z _A ) from a total station S d 'where A is not visible by aiming and reading directly from the total station S.

Its third object is a method for determining planimetric and altimetric coordinates of a target point A (X _A , Y _A , Z _A ) from a total station S from which A is not visible by sight and direct reading from the total station S, using an optical reflection device according to the invention, comprising the following steps according to which:
- the coordinates of any point M (X _M , Y _M , Z _M ) are surveyed from where A and the total station S are inter-visible by direct sighting from S and the distance d _SM is recorded ;
- Said device is placed at the determined point M (X _M , Y _M , Z _M );
- we aim at A by emitting a light ray from S passing through M;
- the distance d _SMA is recorded by laser telemetry from S;
- the distance not reduced to the horizontal d _MA is calculated by the following formula: d _MA = d _SMA - d _SM ;
- A vertical angle V and a horizontal angle H are blocked on the total station S in the direction of M;
- we choose P on the half-line [MA) at the limit of the zone of invisibility, visible by aiming and direct reading from S;
- the coordinates of the point P (X _P , Y _P , Z _P ) are surveyed from S;
- the bearing of the direction MA G _MA is determined from G _MP , with G _MP = G _MA ;
- the coordinates of point A (X _A , Y _A , Z _A ) are calculated according to the following system of equations:
X _A = X _M + dH _MA * sin (G _MA )
Y _A = Y _M + dH _MA * cos (G _MA )
Z _A = Z _M + h _M + d _MA * cos (V _MA ) − h _A
with
dH _MA : reduced horizontal distance from M to A determined by the following formula: dH _MA = d _MA * sin (V _MA );
V _MA : vertical angle between the vertical passing through M and the direction of the light ray reflected from M to A;
h _M : height of the center of the reflecting surface of the mirror at point M (X _M , Y _M , Z _M );
h _A : height of the prism at point A (X _A , Y _A , Z _A ).

Finally, its fourth and last object is a method for determining planimetric and altimetric coordinates of a target point A (X _A , Y _A , Z _A ) from a total station S from which A is not not visible by sighting and direct reading from the total station S, using an optical reflection device according to the invention, comprising the following steps according to which:
- the coordinates of any point M (X _M , Y _M , Z _M ) are surveyed from where A and the total station S are inter-visible by direct sighting from S and the distance d _SM is recorded ;
- the optical reflection device comprising two viewfinders is placed at the determined point M (X _M , Y _M , Z _M ), the normal to the center of the reflecting surface of the mirror being coincident with the axis of the viewfinder of the total station S and the viewfinders of the device in their original positions aiming in the direction of the normal to the mirror on the side of the reflecting surface;
- the zero of the horizontal circle or of the horizontal angle measurement sensor is blocked in the direction of S;
- the first viewfinder is rotated in the direction of A by an angle H from the original position, resulting in a variation of an angle H/2 of the mirror around the same axis without any vertical angular variation, and a rotation of the second viewfinder by an angle V from the original position, around the horizontal axis, causing an angular variation V/2 of the identical mirror without any horizontal angular variation;
- we note the angles H (MS, MA) and V _MA with:
H (MS, MA): reading of the horizontal angle of rotation of the first sight from the origin position in the direction of S, and
V _MA : vertical angle between the vertical passing through M and the direction of the light ray reflected from M to A;
- we aim at A by emitting a light ray from S passing through M;
- the distance d _SMA is recorded by laser telemetry from S;
- the distance not reduced to the horizontal d _MA is calculated by the following formula: d _MA = d _SMA - d _SM ;
- the reduced distance to the horizontal from M to A, dH _MA is calculated using the following formula: dH _MA = d _MA * sin (V _MA );
- the deposit G _SM is calculated;
- the G _MA deposit is calculated using the following formula:
G _MA = G _MS + H (MS, MA)
with G _MS = G _SM + 200 g;
- the coordinates of point A (X _A , Y _A , Z _A ) are calculated according to the following system of equations:
X _A = X _M + dH _MA * sin (G _MA )
Y _A = Y _M + dH _MA * cos (G _MA )
Z _A = Z _M + h _M + (d _MA * cos (V _MA )) − h _A
with
h _M : height of the center of the reflecting surface of the mirror at point M (X _M , Y _M , Z _M );
h _A : height of the prism at point A (X _A , Y _A , Z _A ).

Benefits provided

The invention implemented relates to an optical reflection device making it possible to survey hidden points by offering ease of use by avoiding the movement of the total station, which is a constraint to set up.

The device according to the invention thus allows significant time savings for surveying points hidden by an obstacle, in particular in areas that are difficult to access, for example at sea, or located in a cavity and therefore not visible from the total station.

The device according to the invention also makes it possible to limit the risk of errors when surveying hidden points by minimizing the number of measurements by avoiding the displacement of the total station.

The device according to the invention thus allows the determination of coordinates of hidden points without having to move the topographic material and to create new polygons.

The invention and the advantages resulting therefrom will be better understood on reading the description and the non-limiting embodiments which follow, illustrated with regard to the appended drawings in which:

Figure 1 shows the optical reflection device according to the invention comprising a mirror mounted on a mirror frame. A fork grips said mirror frame and is mounted on a vertical support.

FIG. 2 is a schematic representation of the projection on a horizontal plane of a total station S, of a point A to be surveyed, of an obstacle which hides A from the total station S, of a mirror M of the device for optical reflection according to the invention and of a fictitious point P of the half-line [MA) at the limit of visibility from the total station S.

Figure 3 represents a variant of figure 2 where two possible candidates are represented for the fictitious point P (P and P') in the zones guaranteeing inter-visibility between P and the total station S.

Figure 4 shows the different quadrants in which the deposit can be found.

FIG. 5 represents the projection on a horizontal plane of a total station S, of a point A to be surveyed, of an obstacle which hides A from S, of a mirror M of the optical reflection device according to the invention and of a fictitious point P; it illustrates a first case where (ΔX ≥ 0) and (ΔY > 0) and where the deposit is located in the first quadrant.

FIG. 6 represents the projection on a horizontal plane of a total station S, of a point A to be surveyed, of an obstacle which hides A from S, of a mirror M of the optical reflection device according to the invention and of a fictitious point P; it illustrates a second case where (ΔX ≥ 0) and (ΔY < 0) and where the deposit is located in the second quadrant.

FIG. 7 represents the projection on a horizontal plane of a total station S, of a point A to be surveyed, of an obstacle which hides A from S, of a mirror M of the optical reflection device according to the invention and of a fictitious point P; it illustrates a third case where (ΔX ≤ 0) and (ΔY < 0) and where the deposit is located in the third quadrant.

FIG. 8 represents the projection on a horizontal plane of a total station S, of a point A to be surveyed, of an obstacle which hides A from S, of a mirror M of the optical reflection device according to the invention and of a fictitious point P; it illustrates a fourth case where (ΔX ≤ 0) and (ΔY > 0) and where the deposit is located in the fourth quadrant.

FIG. 9 represents the projection on a horizontal plane of a total station S, of a point A to be surveyed, of an obstacle which hides A from S, of a mirror M of the optical reflection device according to the invention and of a fictitious point P; it illustrates a fifth case where (ΔY = 0) and (ΔX > 0) as well as the orientation of the deposit.

FIG. 10 represents the projection on a horizontal plane of a total station S, of a point A to be surveyed, of an obstacle which hides A from S, of a mirror M of the optical reflection device according to the invention and of a fictitious point P; it illustrates a sixth and last case where (ΔY = 0) and (ΔX < 0) as well as the orientation of the deposit.

FIG. 11 represents a real 3D perspective of a total station positioned at point S at a height h _S , of an optical reflection device according to the invention positioned at point M at a height h _M and of a prism positioned at the fictitious point P at a height h _P by an explanatory diagram of the reduction of the distances to the horizontal.

Figure 12 represents a real 3D perspective of a total station positioned at point S at a height h_S, of an optical reflection device according to the invention positioned at point M at a height h_Mand a prism positioned at the fictitious point P at a height h_Pby an explanatory diagram of a first hypothesis where h > 0 with h = (Z_p+h_p) - (Z_M+ h_M).

FIG. 13 represents a real 3D perspective of a total station positioned at point S at a height h _S , of an optical reflection device according to the invention positioned at point M at a height h _M and of a prism positioned at the fictitious point P at a height h _P by an explanatory diagram of a second hypothesis where h = 0 with h = (Z _p + h _p ) - (Z _M + h _M ).

Figure 14 represents a real 3D perspective of a total station positioned at point S at a height h_S, of an optical reflection device according to the invention positioned at point M at a height h_Mand a prism positioned at the fictitious point P at a height H_Pby an explanatory diagram of the third hypothesis where h < 0 with h = (Z_p+h_p) - (Z_M+h_M).

FIG. 15 is a statement of coordinates obtained by using the optical reflection device according to the invention in the field implementing the first method described according to the invention.

According to the invention, the optical reflection device 1 as illustrated in figure 1 comprises a mirror 2 and a mirror frame 3.

By optical reflection, the applicant means the reflection of at least 90% of light rays in the visible and infrared range. The reflection of light rays in the visible range provides better clarity and that in the infrared range prevents the mirror from heating up.

Preferably, the reflection of the light rays is 95% in the visible and infrared range.

The visible and infrared domains are commonly defined by wavelengths ranging from 400 nm to 800 nm and from 800 nm to 0.1 mm respectively.

For this purpose, the mirror 2 must have a strictly flat surface. Essentially, it is composed of at least one reflective layer on the first surface, preferably aluminum and with a thickness of at least 50 nm, advantageously treated for example with a layer of silicon dioxide (SiO ₂ ) and/or a layer of zirconium dioxide (ZrO ₂ ).

The reflection layer must imperatively be on the first surface of the mirror 2 to optimize the precision of the resulting measurements.

The mirror 2 preferably has another reflective layer on the first surface on the face opposite the first reflective layer.

The optical reflection device 1 according to the invention also comprises a fork 4 and a vertical support 5.

The fork 4 encloses the mirror frame 3 and makes it possible to pivot the mirror 2 around a horizontal and vertical axis.

According to an exemplary embodiment, the fork 4 can form a U and enclose the lower part of the mirror frame 3 as shown in Figure 1.

According to another exemplary embodiment, the fork 4 can frame the entire mirror frame 3.

The fork 4 must be kept fixed in (X, Y, Z) but can rotate around the vertical axis relative to the ground and is advantageously removable.

This fixing is obtained by the use of an advantageously removable vertical support 5 in which the fork 4 is mounted directly above the center of symmetry of the mirror 2 having a reflective layer on at least one, preferably both faces. The vertical support 5 must be stable and robust enough to guarantee the absence of movement of the device according to the invention and better precision of the measurements when surveying points.

By way of non-limiting examples, the vertical support 5 is preferably chosen from a tripod, or any support mounted on a concrete pad or a low wall.

The mirror 2 has a central symmetry on its two faces preferably composed on the first surface of a reflective layer. Thus, the mirror frame 3 and therefore implicitly the mirror 2 can pivot around a horizontal and vertical axis by means of the fork 4. The advantage of being able to pivot the mirror 2 around its two horizontal and vertical axes is to be able to reach the maximum of non-visible points over a larger interval of altitude and a larger interval of bearing values.

Advantageously, the mirror 2 can perform a rotation of 400 grads (g) on itself in its horizontal axis independently of the vertical rotation that it can perform by means of the fork 4.

The mirror 2 is advantageously as light as possible and therefore as thin as possible to facilitate its handling while retaining a certain robustness to avoid breaking.

Mirror 2 is preferably at least 5 mm thick, more preferably 6 mm thick.

The mirror 2 is of any geometric shape provided with a central symmetry, for example, without limitation, rectangular, circular, elliptical or even square.

According to a particular embodiment of the invention, the mirror 2 is rectangular in shape. Rectangular mirrors are the most commonly made and therefore less expensive.

By way of non-limiting example, the mirror 2 of the device 1 according to the invention is rectangular, with a side of 20 cm x 25 cm. This size turns out to be sufficient for professional use of the device 1 and has the advantage of being usual for manufacturers and therefore easy to obtain at a lower cost.

According to a particularly advantageous embodiment of the optical reflection device 1 according to the invention, the improved device 1 comprises two viewfinders mounted on or integrated into the mirror frame 3 and/or on the fork 4, preferably on the fork 4.

A first viewfinder can be positioned either above or below the mirror 2 in its vertical central axis of symmetry, more preferably below the mirror and must be able to rotate in its horizontal axis and in its vertical axis. The improved device 1 also comprises a second viewfinder which can be positioned either to the left or to the right of the mirror 2 in its horizontal central axis of symmetry and must be able to rotate in its vertical axis and in its horizontal axis.

The sights in their original positions aim in the direction of the normal to mirror 2 on the side of the reflecting surface.

The infinitesimal modification of a horizontal angle H changes the vertical sighting plane. The infinitesimal modification of a vertical angle V changes the horizontal sighting plane.

The first viewfinder carries the mirror with it only when it rotates around the vertical axis of the mirror. If it rotates around its horizontal axis, the mirror must not rotate. In other words, this means that if the viewfinder rotates by a certain angle H and a certain angle V from the original position, the mirror will only rotate by an angle H/2 without any variation of its angle V.

The second viewfinder carries the mirror with it only when it rotates around the horizontal axis of the mirror. If it rotates around its vertical axis, the mirror must not rotate. In other words, it means that if the viewfinder rotates by a certain angle H and a certain angle V from the original position, the mirror will rotate only by the same angle V/2 without any variation of its angle H.

The optical reflection device 1 also preferably comprises:
- two pivoting screws located at the level of the graduated circles or the angle measurement sensors, one screw allowing horizontal movement and one screw allowing vertical movement of the mirror 2, or
- A remotely controlled electromechanical system located at the level of the graduated circles or the angle measurement sensors, allowing automated horizontal and vertical movement of the mirror 2; And
- a graduated horizontal circle to measure the Horizontal angles H, positioned at the vertical axis of the mirror 2 below the latter, and a graduated vertical circle to measure the Vertical angles V, positioned at the horizontal axis of the mirror on the left or to the right of the latter, or
- two electronic angle measurement sensors, one to measure Horizontal angles H and one to measure Vertical angles V.

The preferred device 1 according to the invention is equipped with a screw or equivalent electromechanical system for adjusting the mirror 2 in rotation around a vertical axis, the angle of rotation being measured using a graduated horizontal circle or an electronic angle measurement sensor; likewise, it is equipped with a screw or equivalent electromechanical system to adjust it in rotation around a horizontal axis, the angle of rotation being measured using a graduated vertical circle or a measuring sensor electronic angle.

The pivoting screws, or equivalent electromechanical system, advantageously superimposed with the graduated circles or the electronic angle measurement sensors, make it possible to rotate the viewfinders in the desired direction, which will carry with it the mirror 2: the rotation of the first viewfinder by a certain angle H and a certain angle V will drive the mirror only by an angle H/2 without any variation in its angle V. The rotation of the second viewfinder by a certain angle H and a certain angle V will drive the mirror only by the same angle V/2 without any variation of its angle H.

Advantageously, the optical reflection device 1 according to the invention can also integrate a prism tracking system, which will make it possible to automatically detect, for example, the prism at point A or even to manage to detect the sight of the station total s.

Another object of the invention relates to the use of the optical reflection device 1 according to the invention for the determination of planimetric and altimetric coordinates of a target point A (X _A , Y _A , Z _A ) from a total station S from which A is not visible by sighting and direct reading from the total station S.

By planimetric and altimetric coordinates (X, Y, Z), we mean the point on the ground whose coordinates we are trying to determine.

In the various methods for determining planimetric and altimetric coordinates of a target point which is not visible by sighting and direct reading from the total station S described below from the optical reflection device 1 according to the invention, the term more particularly means:
- S (X _S , Y _S , Z _S ) the ground coordinates of the total station or any other equivalent topographic measuring device, such as for example a robotic station, the total station S being positioned vertically to the point S (X _S , Y _S , Z _S ) at a height h _S ;
- A (X _A , Y _A , Z _A ) the ground coordinates of the target point, the prism being positioned in A vertically above point A (X _A , Y _A , Z _A ) at a height h _A ;
- P (X _P , Y _P , Z _P ) the coordinates on the ground of the fictitious point, the prism being positioned in P vertically above the point P (X _P , Y _P , Z _P ) at a height h _P ;
- M (X _M , Y _M , Z _M ) the coordinates on the ground of the optical reflection device 1 according to the invention, the center of the first reflecting surface of the mirror 2 being positioned in M vertically from the point M (X _M , Y _M , Z _M ) at a height h _M .

We give ourselves an origin and a Cartesian reference according to the use in topography. In this frame, the coordinates of the points on the ground of S, A, M and P are thus noted respectively (X _S , Y _S , Z _S ), (X _A , Y _A , Z _A ), (X _M , Y _M , Z _M ) and (X _P , Y _P , Z _P ).

According to an advantageous embodiment of the invention, its subject is a first method for determining planimetric and altimetric coordinates of a target point which is not visible by sighting and direct reading from the total station S comprising the steps described below.

The mirror 2 is positioned so as to be visible from the total station S and the target point A. Concretely, the straight lines (SM) and (MA) do not cross any obstacle, while the straight line (SA) crosses one, as represented in figure 2.

Note that it is not exactly the points on the ground S, M and A which are represented but their projection on a horizontal plane. In reality, the points on the ground S, M and A are generally not at the same level.

The coordinates of any point M (X _M , Y _M , Z _M ) from which A and the total station S are inter-visible are carried out, by direct sighting from the total station S, according to the method usual using a prism (or with the mirror 2 if the normal to its reflecting surface is oriented towards the point S) and the distance d _SM is noted.

By way of illustrative example, when the coordinates of the point M (X _M , Y _M , Z _M ) are determined, a prism is positioned at the point M with a height h _prism which is not necessarily the same height as h _M The Z _M is obtained by calculation as well as the coordinates of the point M (X _M , Y _M , Z _M ) _.

The optical reflection device 1 according to the invention is placed at the point M (X _M , Y _M , Z _M ) thus determined, the center of the first reflecting surface of the mirror 2 being positioned at the point M at a height h _M .

We aim at the prism positioned at A vertically above point A (X _A , Y _A , Z _A ) by emitting a light ray from the viewfinder of the total station S passing through the mirror 2 positioned at M at the vertical from point M (X _M , Y _M , Z _M ) to a height h _M .

The distance d _SMA is recorded by laser ranging from S.

The unreduced distance to the horizontal d _MA is calculated using the following formula: d _MA = d _SMA - d _SM .

A vertical angle V and a horizontal angle H are locked on the total station S in the direction of M, for example using two locking screws in the total station or any other type of locking means, to ensure that they do not do not move while the operator holding the prism at A is guided to move on the half-line [MA) until the prism at P becomes directly visible from the total station S.

We preferably choose P on the half-line [MA) at the limit of the invisibility zone (at the limit of visibility by sighting and direct reading from the total station S), as close as possible to A and as far away of M in order to have a better angular precision.

By noticing that the mirror in M, the prism in P and the prism in A are aligned, we deduce that the angular deviations of A and P are identical with respect to M.

In fact, as illustrated in Figure 3, there are often two candidate points, P and P', on either side of the obstacle. We will advantageously choose P the closest to A and the furthest from M to improve the precision and reduce the error on the angular deviations.

The coordinates of point P (X _P , Y _P , Z _P ) are surveyed from the total station S.

The bearing of the direction MA G _MA is determined from G _MP , with G _MP = G _MA .

To determine the bearing G _MP for any direction (MA), it is then necessary to examine the six possible cases:

According to a first case illustrated by FIGS. 4 and 5, if (ΔX≥0) and (ΔY>0), the first quadrant is considered.
The G _MP deposit is thus calculated using the following formula:
G _MA = G _MP = arctg(ΔX/ΔY),
with :
G _MA = G _MP because M, P and A are aligned;
ΔX = X _P - X _M
ΔY = Y _P - Y _M .

According to a second case illustrated by FIGS. 4 and 6, if (ΔX≥0) and (ΔY<0), the second quadrant is considered.
The G _MP deposit is thus calculated by the following formula:
G _MA = G _MP = 200 - arctg(-ΔX/ΔY),
with :
G _MA = G _MP because M, P and A are aligned;
ΔX = X _P - X _M
ΔY = Y _P - Y _M .

According to a third case illustrated by FIGS. 4 and 7, if (ΔX≦0) and (ΔY<0), the third quadrant is considered.
The G _MP deposit is thus calculated by the following formula:
G _MA = G _MP = 200 + arctg(ΔX/ΔY),
with :
G _MA = G _MP because M, P and A are aligned;
ΔX = X _P - X _M
ΔY = Y _P - Y _M .

According to a fourth case illustrated by FIGS. 4 and 8, if (ΔX≤0) and (ΔY>0), the fourth quadrant is considered.
The G _MP deposit is thus calculated by the following formula:
G _MA = G _MP = 400 - arctg(-ΔX/ΔY),
with :
G _MA = G _MP because M, P and A are aligned;
ΔX = X _P - X _M
ΔY = Y _P - Y _M .

According to a fifth case, if (ΔY=0) and (ΔX>0), the orientation indicated in FIG. 9 is considered.
The G _MP deposit is thus calculated by the following formula:
G _MA = G _MP = 100 g,
with :
G _MA = G _MP because M, P and A are aligned;
ΔX = X _P - X _M
ΔY = Y _P - Y _M .

According to a sixth case, if (ΔY=0) and (ΔX <0), the orientation indicated in FIG. 10 is considered.
The G _MP deposit is thus calculated by the following formula:
G _MA = G _MP = 300 g
with :
G _MA = G _MP because M, P and A are aligned;
ΔX = X _P - X _M
ΔY = Y _P - Y _M .

According to the six possible cases described above, to determine the coordinates of the point A (X _A , Y _A , Z _A ), it is necessary to calculate the reduced distance to the horizontal from M to A, namely dH _MA (illustrated by the figure 11) with:
V _MP = V _MA : the vertical angle between the vertical passing through M and the direction of the light ray reflected from M towards P or towards A; the vertical angle V _MP is the same as V _MA since A and P lie on the same half-line [MA).

To determine dH _MA , one must first calculate dH _MP , with
dH _MP = √ (ΔX ² +ΔY ² )
with :
ΔX = X _P - X _M
ΔY = Y _P - Y _M .

Thus, to determine the distance reduced to the horizontal between M and A, it is first necessary to calculate the vertical angle (V _MP = V _MA ).
The values dH _MA and V _MA = V _MP vary according to the value of h
with :
h = (Z _p + h _p ) - (Z _M + h _M )
h _p : height of the prism at point P;
h _M : height of the center of the reflective surface of mirror 2 at point M (X _M , Y _M , Z _M ).

Thus, three hypotheses are to be considered to carry out the calculation of dH _MA .

According to a first hypothesis illustrated by figure 12, if h > 0 SO :
V_MY=V_PM= arctg (dH_PM/h)
dH_MY=d_MY* sin (V_MY).

According to a second hypothesis illustrated by figure 13, if h = 0 SO :
V_MY=V_PM= 100g
dH_MY=d_MY* sin(V_MY) =d_MY.

According to a third hypothesis illustrated by figure 14, if h < 0 SO :
V_MY=V_PM= 200 – arctg (-dH_PM/h)
dH_MY=d_MY* sin (V_MY).

Finally, the coordinates of point A (X _A , Y _A , Z _A ) are calculated according to the following system of equations:
X _A = X _M + dH _MA * sin (G _MA )
Y _A = Y _M + dH _MA * cos (G _MA )
Z _A = Z _M + h _M + (d _MA * cos (V _MA )) − h _A
with
dH _MA : reduced horizontal distance from M to A; in mathematical terms, it is the length of the projection on the horizontal plane of the segment MA determined by the following formula: dH _MA = d _MA * sin (V _MA );
V _MA : vertical angle between the vertical passing through M and the direction of the light ray reflected from M to A;
h _M : height of the center of the reflective surface of mirror 2 at point M (X _M , Y _M , Z _M );
h _A : height of the prism at point A (X _A , Y _A , Z _A ).

According to another advantageous embodiment of the invention, its subject is a second method for determining planimetric and altimetric coordinates of a target point which is not visible by sighting and direct reading from the total station S including the steps described below.

The coordinates of any point M (X _M , Y _M , Z _M ) are surveyed from where A and the total station S are inter-visible by direct sighting from S and the distance d _SM is recorded.

The improved optical reflection device 1 according to the invention comprising two viewfinders is placed at the determined point M (X _M , Y _M , Z _M ), the normal to the center of the reflecting surface of the mirror 2 being coincident with the axis of the viewfinder of the total station S and the viewfinders of the device 1 in their original positions aiming in the direction of the normal to the mirror 2 on the side of the reflecting surface.

Advantageously, the zero of the horizontal circle or of the horizontal angle measurement sensor is blocked in the direction of S.

We can then proceed in the following manner to survey point A (X _A , Y _A , Z _A ).

The first sight is rotated in the direction of A until it is aligned with A and an angle H (MS, MA) is taken from the original position indicated by the graduated horizontal circle or the sensor horizontal angle measurement, resulting in a variation of an angle H / 2 of the mirror 2 around the same axis without any vertical angular variation.

Alternatively, as long as the zero of the horizontal circle or of the horizontal angle measurement sensor is not blocked in the direction of S, one can differentiate between the angle of arrival and the angle of departure to get H (MS, MA).

The second viewfinder is rotated in the direction of A until the prism at point A (X _A , Y _A , Z _A ) is visible from the total station S passing through the center of the first reflective surface of the positioned mirror at point M (X _M , Y _M , Z _M ) and an angle V _MA indicated by the graduated vertical circle or the vertical angle measurement sensor is noted, then resulting in an identical angular variation V/2 of the mirror 2 without any angular variation in horizontal. The zero of the angle V _MA is located on the vertical passing through M and the angles are counted positively from top to bottom with a maximum of 200 grads or 180°.

Advantageously, these angles are communicated to the total station, for example by means of a wireless connection established between an electronic system integrated in the optical reflection device 1 according to the invention and the total station so that the total station has of all the data needed to calculate the coordinates of point A (X _A , Y _A , Z _A ).

We thus know the angles H (MS, MA) and V _MA with:
H (MS, MA): reading of the horizontal angle of rotation of the first sight from the origin position in the direction of S, and
V _MA : vertical angle between the vertical passing through M and the direction of the reflected light ray from M to A while the angle of rotation of the second viewfinder from the original position in the direction of S corresponds to V (MS, MY) ;

We aim at A by emitting a light ray from S passing through M.

Thus, the non-reduced horizontal distance d _SMA is recorded by laser telemetry from S and the non-reduced horizontal distance d _MA is calculated by the following formula: d _MA = d _SMA −d _SM .

Consequently, the distance reduced to the horizontal from M to A, dH _MA is calculated by the following formula: dH _MA = d _MA * sin (V _MA ) with V _MA : vertical angle between the vertical passing through M and the direction of the light ray reflected from M to A.

We therefore know in the horizontal plane dH _MA which is in fact the distance between the horizontal projections of these points. We also know the horizontal angle between the projections of S, M and A, that is to say H (MS, MA).

The bearing G _SM is calculated according to one of the six possible cases described above.

The G _MA deposit is calculated with the following formula:
G _MA = G _MS + H (MS, MA)
with :
_GMS = _GSM + 200g
G _MS is different from G _SM , the former is the angle between north and the MS direction, and the latter is the angle between north and the SM direction. We therefore add 200 degrees or 180 degrees more;
H (MS, MA): the angle H (MS, MA) is always read in the same direction as the bearings, ie clockwise.

We then calculate the coordinates of point A (X _A , Y _A , Z _A ) according to the following system of equations:
X _A = X _M + dH _MA * sin (G _MA )
Y _A = Y _M + dH _MA * cos (G _MA )
Z _A = Z _M + h _M + (d _MA * cos (V _MA )) − h _A
with
h _M : height of the center of the reflective surface of mirror 2 at point M (X _M , Y _M , Z _M );
h _A : height of the prism at point A (X _A , Y _A , Z _A ).

Examples

Example 1: Validation of the use of the optical reflection device according to the invention to survey the coordinates of a point by the implementation of the first method described by comparison with the survey from a total station
The difference between the coordinates of the "visible" point A surveyed directly by the total station and those surveyed through the optical reflection device 1 according to the invention, and more particularly the center of the reflecting surface of the mirror 2, located at the point " M” was calculated.
FIG. 15 shows the list of coordinates surveyed in the field for the implementation of the first method according to the invention.
From these coordinates, the bearing G _MA (= G _MP ) is calculated as follows:
ΔX = X _P – X _M = 10.241 – 11.064 = - 0.823 m ≤ 0 and
ΔY = Y _P – Y _M = - 3.029 – 0 = - 3.029 < 0
The third case described above is applicable in which: if (ΔX ≤ 0) and (ΔY < 0).
The deposit (G _MA ) is therefore given by the following formula:
G _MA = G _MP = 200 + arctg(ΔX/ΔY)
= 216.88965g.
Or dH _MA = 4.192 m: this is the Euclidean distance between M and A.
Thus, X _A = X _M + dH _MA * sin (G _MA ) = 11.064 + 4.192 * sin (216.88965) = 9.9648 m
and X _A TRUE = 9.961 m
So ΔX = 9.9648 – 9.961 = 3.8 mm
Similarly, Y _A = Y _M + dH _MA * cos (G _MA ) = 0 + 4.192 * cos (216.88965) = - 4.0453 m
and Y _IS TRUE = - 4.037 m
So ΔY = - 4.0453 – (- 4.037) = - 8.3 mm
Δd = √ (ΔX ² + ΔY ² ) = 9.1 mm
Z _A = - 0.027m
And Z _A TRUE = - 0.034 m
So ΔZ = - 0.027 – (-0.034) = 7 mm
From the results thus obtained, there is a difference between the true point “A” and the point “A” surveyed through the mirror of the device according to the invention of 9.1 mm in Euclidean distance and 7 mm in altitude.
This centimetric precision shows that this method according to the invention is therefore reliable, feasible and applicable in the field of topography.

Claims (10)

Optical reflection device (1), characterized in that it comprises:
- a mirror (2) with a strictly flat surface, having at least one reflective layer on the first surface with a reflection rate of at least 90% in the visible and infrared range and a center of symmetry;
- a mirror frame (3);
- a fork (4) which encloses said mirror frame (3) and makes it possible to pivot the mirror (2) around a horizontal and vertical axis; And
- a vertical support (5), fixed in said fork (4) and located directly above the center of symmetry of said first reflecting surface of said mirror (2). Optical reflection device (1) according to claim 1, characterized in that it further comprises another reflective layer on the first surface on the face opposite the first reflective layer. Optical reflection device (1) according to Claim 1 or 2, characterized in that the reflecting layer is made of aluminum and is at least 50 nm thick. Optical reflection device (1) according to one of Claims 1 to 3, characterized in that the mirror (2) is at least 5 mm thick, preferably at least 6 mm thick and of any geometric shape provided with a central symmetry, preferably rectangular with sides of 20 cm x 25 cm. Optical reflection device (1) according to one of Claims 1 to 4, characterized in that it further comprises two viewfinders, mounted on the mirror frame (3) and/or on the fork (4), being understood that:
- said first viewfinder in an original position aims in the direction of the normal to the mirror (2), on the side of the reflecting surface, and a rotation of said first viewfinder by an angle H from the original position, around a horizontal axis, causes a variation of an angle H/2 of the mirror (2) around the same axis without any vertical angular variation;
- said second viewfinder in an original position aims in the direction of the normal to the mirror (2), on the side of the reflecting surface, and a rotation of said second viewfinder by an angle V from the original position, around a vertical axis, results in an identical angular variation V/2 of the mirror (2) without any horizontal angular variation. Optical reflection device (1) according to Claim 5, characterized in that it comprises:
- two pivoting screws, one screw allowing horizontal movement and one screw allowing vertical movement of the mirror (2), or
- a remote-controlled electromechanical system, allowing automated horizontal and vertical movement of the mirror (2); And
- a graduated horizontal circle and a graduated vertical circle to measure the Horizontal angles H and the Vertical angles V, or
- two angle measurement sensors, one to measure Horizontal angles H and one to measure Vertical angles V. Use of the optical reflection device (1) according to one of Claims 1 to 6 for determining planimetric and altimetric coordinates of a target point A (X _A , Y _A , Z _A ) from a total station S from where A is not visible by aiming and direct reading from the total station S. Method for determining planimetric and altimetric coordinates of a target point A (X _A , Y _A , Z _A ) from a total station S from which A is not visible by sighting and direct reading from the total station S, using an optical reflection device (1) according to one of Claims 1 to 6, comprising the following steps according to which:
- the coordinates of any point M (X _M , Y _M , Z _M ) are surveyed from where A and the total station S are inter-visible by direct sighting from S and the distance d _SM is recorded ;
- Said device is placed at the determined point M (X _M , Y _M , Z _M );
- we aim at A by emitting a light ray from S passing through M;
- the distance d _SMA is recorded by laser telemetry from S;
- the distance not reduced to the horizontal d _MA is calculated by the following formula: d _MA = d _SMA - d _SM ;
- A vertical angle V and a horizontal angle H are blocked on the total station S in the direction of M;
- we choose P on the half-line [MA) at the limit of the zone of invisibility, visible by aiming and direct reading from S;
- the coordinates of the point P (X _P , Y _P , Z _P ) are surveyed from S;
- the bearing of the direction MA G _MA is determined from G _MP , with G _MP = G _MA ;
- the coordinates of point A (X _A , Y _A , Z _A ) are calculated according to the following system of equations:
X _A = X _M + dH _MA * sin (G _MA )
Y _A = Y _M + dH _MA * cos (G _MA )
Z _A = Z _M + h _M + (d _MA * cos (V _MA )) − h _A
with
dH _MA : reduced horizontal distance from M to A determined by the following formula: dH _MA = d _MA * sin (V _MA );
V _MA : vertical angle between the vertical passing through M and the direction of the light ray reflected from M to A;
h _M : height of the center of the reflective surface of the mirror (2) at point M (X _M , Y _M , Z _M );
h _A : height of the prism at point A (X _A , Y _A , Z _A ). Method according to Claim 8, where P at the limit of the zone of invisibility is chosen as close as possible to A and as far as possible from M in order to have better angular precision. Method for determining planimetric and altimetric coordinates of a target point A (X _A , Y _A , Z _A ) from a total station S from which A is not visible by sighting and direct reading from the total station S, using an optical reflection device (1) according to claim 5 or 6, comprising the following steps:
- the coordinates of any point M (X _M , Y _M , Z _M ) are surveyed from where A and the total station S are inter-visible by direct sighting from the total station S and the distance d _SM ;
- the optical reflection device (1) comprising two viewfinders is placed at the determined point M (X _M , Y _M , Z _M ), the normal to the center of the reflecting surface of the mirror (2) being coincident with the axis of the viewfinder of the total station S and the viewfinders of the device (1) in their original positions aim in the direction normal to the mirror (2) on the side of the reflecting surface;
- the zero of the horizontal circle or of the horizontal angle measurement sensor is blocked in the direction of S;
- the first viewfinder is rotated in the direction of A by an angle H from the original position, resulting in a variation of an angle H/2 of the mirror around the same axis without any vertical angular variation, and a rotation of the second viewfinder by an angle V from the original position, around the horizontal axis, causing an angular variation V/2 of the identical mirror without any horizontal angular variation;
- we note the angles H (MS, MA) and V _MA with:
H (MS, MA): reading of the horizontal angle of rotation of the first sight from the origin position in the direction of S, and
V _MA : vertical angle between the vertical passing through M and the direction of the light ray reflected from M to A;
- we aim at A by emitting a light ray from S passing through M;
- the distance d _SMA is recorded by laser telemetry from S;
- the distance not reduced to the horizontal d _MA is calculated by the following formula: d _MA = d _SMA - d _SM ;
- the reduced distance to the horizontal from M to A, dH _MA is calculated using the following formula: dH _MA = d _MA * sin (V _MA );
- the deposit G _MS is calculated;
- the G _MA deposit is determined by the following formula:
G _MA = G _MS + H (MS, MA)
with :
_GMS = _GSM + 200g
- the coordinates of point A (X _A , Y _A , Z _A ) are calculated according to the following system of equations:
X _A = X _M + dH _MA * sin (G _MA )
Y _A = Y _M + dH _MA * cos (G _MA )
Z _A = Z _M + h _M + (d _MA * cos (V _MA )) − h _A
with
h _M : height of the center of the reflecting surface of the mirror (2) at point M (X _M , Y _M , Z _M );
h _A : height of the prism at point A (X _A , Y _A , Z _A ).