ITTO20100719A1 - GEO-SPACIAL COOPERATIVE POSITIONING SYSTEM OPERATING WITH GLOBAL SATELLITE NAVIGATION SYSTEMS AND WIRELESS TELECOMMUNICATION NETWORKS, RELATED PROCEDURE AND GEO-SPACIAL POSITIONING APPARATUS - Google Patents

Description

DESCRIPTION of the industrial invention entitled: â € œCooperative geo-spatial positioning system operating with satellite global navigation systems and wireless telecommunication networks, relative method and geo-spatial positioning apparatusâ €

TEXT OF THE DESCRIPTION

The present invention relates to a cooperative geospatial positioning system configured to operate in association with a GNSS satellite global navigation system comprising a plurality of satellites transmitting GNSS signals, said system comprising a set of geospatial positioning apparatuses, comprising respective receivers for GNSS signals and configured to estimate the positioning of the apparatus by processing data in said GNSS signals received from satellites visible in said plurality of satellites, said positioning estimate also being based on positioning aid data provided by other network positioning apparatuses, being said geospatial positioning apparatuses provided with wireless communication means to operate as a peer in a peer-to-peer wireless communication network and exchange wireless data with one or more other peers of said peer-topeer network .

Typically a GNSS receiver is able to estimate its position only if the respective geo-spatial positioning apparatus, for example a GPS terminal, is in optimal conditions for the visibility of the satellites (at least four satellites in sight, i.e. at least four signals received with sufficient power). The positioning devices can be found in non-optimal conditions of visibility, for example because they are inside a building, or under trees, or behind a window and receive too weak satellite signals. Therefore in these cases the estimation of the position may be slowed down, if not made impossible. Furthermore, such GNSS receivers usually make use of Kalman filters. The GNSS receiver reduces errors by using techniques such as the Kalman filter to mitigate the effects of noise, which makes a single estimate of position, time and velocity (PVT estimate) more or less variable. It is clear that the not full visibility of a sufficient number of satellites makes it difficult to initialize this Kalman filter and therefore to perform the position estimation.

To overcome such problems, assisted GNSS procedures are known in the state of the art where information that improves the speed or accuracy of positioning is provided to the positioning devices from a base station or server via a dedicated wireless connection. . In this context, for example, Assisted GPS is currently operating.

This technology has drawbacks, since the information of this centralized base station is not always the most suitable for each positioning apparatus and its position: the distance between the base station or server that provides the information and the positioning apparatus that receives them means that these may not be sufficiently precise to be useful, both for the distance and because the configuration of satellites seen by the base station or server may be different from that seen locally by the positioning device.

The present invention has the purpose of providing a cooperative geo-spatial positioning system operating positioning in association with GNSS systems that allows to initialize the Kalman filter of the GNSS receiver and to rapidly perform the estimation of the position also for geospatial positioning apparatuses which are in non-optimal conditions of visibility, providing local information that improves the accuracy and / or speed of positioning.

According to the present invention, this object is achieved thanks to a geospatial positioning system having the characteristics referred to specifically in the following claims.

The invention also relates to a corresponding geo-spatial positioning process and a geo-spatial positioning apparatus for use in such a geo-spatial positioning system.

The geospatial positioning system and procedure according to the invention allow to provide a specific geospatial positioning apparatus with information relating to positioning data of other apparatuses present in the network and such as to represent an aid for an apparatus that is in conditions not optimal with respect to the constellation of GNSS satellites.

Further characteristics and advantages of the invention will emerge from the following description with reference to the attached drawings, provided purely by way of non-limiting example, in which:

- figure 1 represents a schematic sectional view of a system according to the invention.

In short, the proposed solution concerns a geo-spatial positioning system operating in association with GNSS systems (Global Navigation Satellite System), where a plurality of GNSS satellites transmit GNSS data to a set of geospatial positioning devices, including a respective receiver for GNSS signals and configured to operate the positioning by processing data of the GNSS signals received from satellites visible to them, by measuring from such data, in particular by processing the GNSS signal, of a set of positioning aid quantities, such geospatial positioning apparatus also including wireless communication means to operate as a peer in a peer-to-peer wireless communication network, receiving help wireless data from one or more other peers of that network. The system according to the invention provides that at least one geo-spatial positioning device, which is a peer in the wireless communication network, is able to operate as an assisted device or peer, estimating the respective position on the basis of a height, in particular on the reference ellipsoid (for example WGS84) used for positioning, estimated by this geo-spatial positioning apparatus on the basis of values of such height that it is able to receive from the other peers of this wireless communication network , this estimated height being calculated through weighted average operations on these values received from several other peers, the weight coefficients for the weighted average operation being transmitted by these other peers or calculated to the positioning apparatus.

More specifically, the invention relates to an assisted geo-spatial positioning apparatus that implements a position estimation procedure in which an estimated height, calculated by such aided apparatus on the basis of the position data received from the peers of the wireless communication network with which it can communicate directly, it is used as an additional measure available for estimating the position.

The sharing by the peers of the wireless network of the heights measured by each peer is useful in order to improve the quality of the position estimate provided by a receiver capable of exploiting this data and also allows to estimate the position of the user in presence of only three satellites.

The system according to the invention is now described in more detail.

Figure 1 schematically shows a positioning system according to the invention.

With S is indicated as a whole a system of satellites, in figure 1 four satellites S1, S2, S3 and S4, which transmit global satellite navigation signals D, i.e. GNSS signals, to a set of geo-spatial positioning devices indicated as a whole with U, for example user terminals; in particular, figure 1 shows, by way of example, five geo-spatial positioning devices U1â € ¦U5.

These positioning devices U1â € ¦U5 in general receive such global satellite navigation signals D, indicated in figure 1 more specifically with D1â € ¦D4, indicating through the subscript the respective satellite S1â € ¦S4 which transmits the satellite signal, and acquire these signals GNSS D processing them to obtain information necessary to calculate the position. The GNSS data transmitted in such GNSS D signals usually include, as the message content, information necessary for positioning such as data from the on-board clock and satellite positions, more precisely the ephemeris.

These D signals transmitted by the GNSS systems are also processed to the geo-spatial positioning apparatus to measure the positioning aid quantities, that is, additional parameters with respect to the information immediately necessary for positioning and already present in the information content of the satellite signal. , i.e. navigation messages, such as ephemeris.

These positioning devices U1â € ¦U5 also represent, through their respective wireless communication modules, peer or peer nodes of a wireless peer-to-peer W communication network, for example a WI-FI network, or Wave, or Bluetooth or Ultrawideband, which exchanges data over respective wireless connections. Figure 1 shows some of these connections, W11â € ¦W45, where the subscripts represent the positioning devices U1â € ¦U5 between which they operate.

It should therefore be noted that the term geo-spatial positioning apparatus for the purposes of this description means a device equipped with a receiver P for global satellite navigation signals (GNSS), for example a commercial uBlox5 receiver, and a transceiver module / wireless communication T, this category of equipment including different types of computers, including notebooks, tablet-PCs, palmtop computers, mobile phones, satellite navigators.

The system according to the invention provides that such positioning apparatuses U represent peers within the wireless network W peer-to-peer. Given a satellite in the set of satellites S, some of the U apparatuses see them with an excellent quality of received signal, this quality being known as 'open sky', others see them instead with a lower quality of received signal, called quality 'light indoor', because they are located inside buildings, or under trees, or behind a window.

In the following we will adopt the term geo-spatial positioning apparatus or, alternatively, the denomination of peer when we want to highlight the role of this geo-spatial positioning apparatus within the wireless W peer-to-peer connection network.

As can be seen in figure 1, among the U apparatuses, there are some apparatuses, such as U2, U4, U5, which, in the example shown here, receive excellent quality global satellite navigation signals D from all four satellites S1â € ¦S4necessary, ie they have all four of them visible in the open sky, and therefore they have all the data to quickly acquire and evaluate the position. U1Ã instead indicates an apparatus that sees some of the satellites with good signal quality (in open sky) and others with lower signal quality (light indoor). Finally, the U3 geospatial positioning apparatus does not see any satellite in open sky but sees them all in indoor light conditions.

Apparatuses that see at least four satellites in open sky have no problem acquiring their signals in a very short time and calculating their position. The apparatuses that see some of the 4 necessary satellites in indoor light mode, have difficulty acquiring their signals and evaluating their position. In the positioning system according to the invention it is envisaged that, given a peer positioning device, for example U1, which may not have a sufficient number of S1â € ¦S4 satellites in open sky view, one or more of the other devices peers who have already hooked up to the signals of a sufficient number of satellites, i.e. U2, U4, U5, operate as a peer aid apparatus, or aiding peer, U to such positioning apparatus U1, peer with respect to the wireless communication network W, which is therefore aided, that is, it is a helped peer, or aided peer, Uu.

For the purposes of this description, j is an index that specifies the helper peer Uafra a number N of helper peers that, based on the configuration and status of the wireless network W, are able to help a particular aided peer Uu, for example because they are within a limit distance, generally determined by the wireless network W used, transmitting, as an aid data, their own height, hereinafter referred to as â € œhelping height to such aided peer Uu, as better detailed below. In general, each of the positioning devices U can constitute a helping peer, indicated in general with the reference Ua, or an assisted peer, indicated in general with the reference Uu, according to the conditions of visibility and availability of connections in the communication network. wireless peer-topeer.

This assistant peer Uadunque, for example U2, is configured to measure, by treating the signal D received by the satellite through its own microprocessor and its own signal processing capabilities, a set of help quantities including its own position, i.e. the three coordinates position cartesians {xj, yj, zj} and its own height hj, and send them, through the wireless communication network W to an assisted peer Uuad for example U1o U3, which does not have a sufficient number of satellites in open sky view.

The helped peer Uuel processes the help quantities, received from a number N of helping peers Ua, in order to:

- initialize the Kalman filter of your GNSS signal receiver P, if it does not have at least four satellites in sight,

- calculate a help height haid, on the basis of the individual help heights hj received,

- estimate your position on the basis of your measurements made on the basis of the received GNSS signals and of the aided height you have estimated.

For example, the peer assistant U2 has full visibility of the necessary satellites and the possibility of processing the GNSS signals D1, D2, D3 and D4 received from the S1â € ¦S4 satellites, to obtain for example their own position coordinates {x2, y2, z2} and their own h2 height, which it sends over the wireless connection W23 to the aided peer U3, which, on the other hand, does not have full visibility of any satellite. Then, an assisting peer, for example U2, measures a set of positioning aid quantities, transmitting them over the wireless network W, to another geospatial positioning apparatus, corresponding to the assisted peer Uu.

According to a relevant aspect of the invention, the helping peer Uap can optionally send to the assisted peer Uu, together with the help height hj, also the corresponding accuracy parameters βj, representative of how much the corresponding height hj transmitted by the j-th peer helper can be trusted by other U peers on the network.

The assisted peer, for example U3, receives one or more of the positioning aid quantities from a number N of assisting peers, generally greater than 1; with reference to the example of figure 1, the assisted peer U3 receives the positioning aid quantities from the three peers U2, U4, U5 which are directly connected, but can also receive these positioning aid quantities through an indirect path, which it passes for example through node U1 (single hop or multi-hop mode).

According to a main aspect of the invention, the assisted peer, for example U3, processes the values of height and position received in order to obtain estimated values useful for improving its positioning capabilities, by means of a weighted average operation.

By indicating with {xj, yj, zj, hj} the position and help height data received from the j-th assistant peer, the assisted peer Uuelabora (all or part of) the help heights hj received in order to obtain the height aid haid, useful for improving its positioning capacity, according to a weighted average operation:

No.

h aid <=> Ã ¥ a j h j (1)

j = 1

where hjà indicates the aid height measured and transmitted by the peer assistant Uaj-th, Î ± jà ̈ the coefficient or weight corresponding to the aid height hj, to be used in the calculation of the weighted average, haid indicates the assisted height, i.e. the estimated value of the assisted peer using the N assisting heights obtained from the N assisting peers Ua.

The weight coefficients Î ± j can be chosen according to the following criteria:

- as a uniform average with respect to the number N of helping peers Ua, i.e. Î ± j = 1 / N, if the peers Ua have similar characteristics and are in similar conditions, or if it is not possible to evaluate the quality or reliability of individual peers,

- the weight coefficient is set equal to an accuracy parameter, that is Î ± j = βj, in the event that in the wireless network W the presence of equipment defined as anchor peers is contemplated, i.e. equipment equipped with professional GNSS receivers, capable of provide a more accurate position estimate than a commercial receiver. An anchor peer can be attributed a greater weight than other peers equipped with commercial receivers. By defining a virtual number of Nvirt peers:

<N> virt <= N> gen <+ w> anc <N> anc (2)

where Ngen indicates the number of generic peers with which the assisted peer is able to establish a direct link, Nanc indicates a number of anchor peers with which the assisted peer is able to establish a direct link, <w> anc <ÃŽ [1 , + ¥)> indicates the weight attributed to the positioning aid quantities provided by the anchor peers, it is possible to define the accuracy parameter βj as:

It is <1>, for generic unpeer

à ̄à ̄ Nb = à virt

j (3) Ã ̄ w anc, for unanchor peer

à ̄ î N virt

If in the wireless communication network W it is possible to carry out ranging measurements between peers, it is possible to set the weight Î ± j equal to a distance parameter Î · j ,, a function of the distance between the peers. Peers must be equipped with radio devices enabled to estimate the distance between peers, distance measurements can be performed using known `` radio ranging '' techniques, based for example on Received Signal Strength (RSS ), Time of Arrival (TOA), Time Difference of Arrival (TDOA) or Round Trip Time (RTT). This distance is typically calculated by the aided peer, but could also be calculated by the helping peer. In this case, called dj the distance between the assisted peer and the j-th assistant peer, it is possible to define for example the distance parameter Î · j as:

- d

and j

h j = N

à ¥ e - d i (4)

i = 1

that is, the ratio between the exponential of the distance dja at which a certain assistant peer Ua is found and the sum of the exponentials of all the distances of the N helping peers Ua.

In general, the weights used to calculate an aid quantity such as the aid height can be calculated from data obtained from the W wireless peer-to-peer communication network or the satellite navigation system.

According to a further aspect of the system according to the invention, the aided geo-spatial positioning apparatus associated with aided height has a parameter called reliability index r, which is used to define the variance of the error relative to the measurement of height inside a covariance matrix of the measurement errors R of the Kalman filter implemented in the GNSS signal receiver P of the assisted positioning apparatus Uu. In general, it is envisaged to use a quantity inversely proportional to the square of the reliability index r as variance of the height measure to be inserted in said covariance matrix R.

In the case in which the peer helped Uu has only three satellites in visibility, the reliability index r is defined by means of a function inversely proportional to the root of an evaluated variance, between each help height h and the estimated height haid, on the N peer helpers Ua:

1

r = N

à ¥ a22 (5)

j <(> hj- haid <)>

j = 1

In the event that the assisted peer has four or more satellites visible, the reliability index r is defined by a relationship similar to (5):

1

r = N

<(> Nsat-2 (6)

<)> Ã ¥ at <2> h 2

j <(> hj- 0 <)>

j = 1

where, however, indicating with h0 a height estimated by the assisted peer Uu using only GNSS data, a variance of the assisting heights hj is used with respect to this height h0 estimated using only the GNSS data received from the assisted peer Uu; furthermore, the root of this variance is corrected by multiplying it by a factor equal to a number of satellites in visibility Nsat reduced by two. The assisted height haide the reliability index r are processed by a Kalman filter inside the GNSS signal receiver P of the assisted apparatus Uu. The estimated value of assisted height calculated by the assisted peer Uura represents an additional measurement available to its receiver P. Since the Kalman filter inside the receiver P is an extended Kalman filter, the actual available measurement is given by the difference haid-hs, where hs denotes an estimate of height obtained from the position of the Kalman model. The Kalman filter inside the P receiver does not undergo structural changes. H indicates a measurement matrix associated with this Kalman filter, which allows you to predict the difference between the measurement and the prediction of the measurement. The procedure for obtaining the matrix H of the directing or measuring cosines is per se known in literature. It is planned to add a further row to this measurement matrix H relative to this additional available measurement, ie the estimated value of aided height haid. It is thus possible to derive from the matrix H a matrix G which relates the errors in the latitude-longitude-height system and the errors in the ECEF (Earth-Centered Earth-Fixed:

à © D x ù à © g11 g12 g 13 ù à © D f ù

ê yú ê ú

ê D ú = êg ú

ê 21 g22 g 23úê D lú (7)

ê à «D z ú ê» ê à «g 0 g ú ê" ê

14314244333 à «D h ú û

G.

where D x, D y, D z indicate the errors with respect to the position coordinates x, y, z, while D f, D l, D h indicating the errors with respect to latitude, longitude and height, f, Î », h. The coefficients of the matrix G, whose calculation procedure in general derives from a known treatment, reported for example in Saurabh Godha, â € œPerformance Evaluation of Low Cost MEMS-Based IMU Integrated With GPS for Land Vehicle Navigation Applicationâ €, 2006 (( URL: http://www.geomatics.ucalgary.ca/research/publications/Grad Theses.html) are:

g 11 = Acosfcosl- (Nv h) symf cos l

g 12 = - (Nv h) cosf sin l

g 13 = cosl cos f

g 21 = Acosfsinl- (Nv h) symf sin l

g 22 = (Nv h) cosf cos l (8) g 23 = sinl cos f

g 31 = A (1-e2

) sinf + Nv (1-e 2

) cosf h cos f

A = -ae <2> sinfcosf / (1 - e <2> sin <2 3> f)

where Nv here indicates the radius of curvature of the first vertical, and indicates the eccentricity of the reference ellipsoid, a indicates the semi-major axis of the ellipsoid, h indicates the height of the assisted apparatus Uu, f indicates the latitude of the assisted apparatus Uue Î »indicates the longitude of the assisted apparatus Uu.

Since the only value of interest is given by the error in height D h, only the last line of the inverse of the matrix G is taken into consideration.

In the system according to the invention it is also possible to implement an iterative aid procedure, applicable in the presence of three satellites, which provides for the following operations:

a) perform an initialization operation on the assisted peer U, including the steps of:

- estimate an initial position of the assisted peer Uup0 [0] = [x0 [0], y0 [0], z0 [0]] as the arithmetic mean of the position coordinates {xj, yj, zj} received from each helping peer Uaa a 0 or initial time of the iterative procedure,

- estimate a misalignment of the clock of the assisted peer receiver t [0] using the starting position p0 [0] and pseudorange measurements, i.e. the geometric distance between a GNSS receiver and a given satellite, available, in particular three corresponding pseudorange measurements to the three visible satellites;

- initialize an initial assist height value haid [0] equal to the average, which can be weighted, of the assist heights hj received at time 0;

- initialize a variance of the height measurement error in the covariance matrix of the measurement errors R of the Kalman filter with a higher value than that obtainable from the pseudorange measurements;

b) perform a recursion operation to the assisted peer Uucompanying the steps of:

- calculate through an iteration of the Kalman filter the PVT (Position Velocity and Time) values, obtaining a position p0 [k] and a misalignment of the clock t [k] at time k, using GNSS data from the three visible satellites and the value of estimated height haid [k] at that instant k,

- use the position p0 [k] at instant k to calculate a GNSS estimate of the height at time kh <Ë † +> [k]

- calculate the second order moment of the help heights hj with respect to the Kalman estimate

<+>

height <hË † [k]> and use it to update the element of the error covariance matrix R relative to the height measurement,

- calculate a new aided height haid [k + 1] as a weighted average of the Kalmandell estimateâ € ™ height <hË † +>

<[k]> at time k and the current aided height haid [k], using a weight w that can be set according to the application,

iterate the recursion operation.

In summary, the system according to the invention can operate in the following conditions:

- the peer helped Uuha four or more satellites into visibility. In this circumstance, the assisted peer Uu uses the help heights h and the reliability index r to improve the performance of the GNSS signal receiver P with which the assisted peer Uuà is equipped;

- the peer helped Uuha three satellites into visibility. In this circumstance, the assisted peer Uu uses the help heights h and the reliability index r to evaluate its position using both the help data and the GNSS signals provided by the assisted peer Uu;

- the aided peer Uu has three satellites in visibility and uses the iterative aid procedure to recursively compute the aided height estimate value haide the covariance matrix R, in order to improve position estimation based on data from the satellites in visibility and the aided height estimate value has been recursively calculated.

The solution described above has several advantages over the known art.

The cooperative positioning system according to the invention advantageously allows to obtain, through help heights provided by peers who have full visibility of the peer satellites that do not have open sky visibility of a sufficient number of satellites, an improvement in performance and the possibility of making a position estimate even for peers in conditions that do not allow an independent estimate of the position (for example because they are inside a building and do not receive a sufficient number of satellite signals). Advantageously, the proposed system implements a position estimation procedure, in which an assisted height, calculated by the assisted peer on the basis of the position data received from the assisting peers with whom it is able to communicate directly, is used as a further measure available for estimating the position. The sharing by the peers of the heights is useful in order to improve the quality of the position estimate provided by a receiver capable of exploiting this data and also allows to estimate the user's position in the presence of only three satellites.

The heights provided by the system according to the invention come from a nearby user or node, rather than from a distant server as in the case of the AGNSS, which has advantages since these heights have greater validity the more local they are, therefore they cannot be provided by the AGNSS, but can instead be received by a nearby device such as a peer of a wireless network; moreover, the system according to the invention provides a combination mechanism which advantageously combines the information coming from different nodes, also allowing to take into account the distribution of the nodes and the operating conditions.

Furthermore, advantageously, the exchange of information envisaged by the system according to the invention appears to be perfectly integrated in the vision of cooperative user networks in development, such as vehicular networks, internet of things, communities.

Furthermore, advantageously, the peer to peer exchange allows forms in which information is exchanged between users for free, while this is more difficult, also for management costs, in the case of centralized supply of information as in the Assisted-GNSS case.

Naturally, the principle of the invention remaining the same, the details of construction and the embodiments may vary widely with respect to those described and illustrated purely by way of example, without thereby departing from the scope of the present invention.

Possible fields of application of the proposed system include both the positioning in open sky scenarios where the system according to the invention would allow to calculate the position more quickly and / or improve the accuracy, and indoor light scenarios, where the system according to the Invention would allow to calculate the position in conditions in which this would be impossible or would require a very long time, so much so as to be sometimes impossible, and / or improve accuracy.

The system and procedure according to the invention can be applied to any assisted peer, even if it has four open sky satellites, even if the most significant improvements are obtained for assisted peers who do not have four open sky satellites. The system and method according to the invention are however not to be considered limited to peers with a specific number of satellites in sight with a given quality, being able in general to help improve the estimation of the position even in cases in which it is already sufficiently precise.

Claims (11)

CLAIMS 1. Cooperative geo-spatial positioning system configured to operate in association with a GNSS satellite global navigation system comprising a plurality of satellites (S) transmitting GNSS signals (D), said system comprising a set of geo-spatial positioning equipment ( U), comprising respective receivers for GNSS signals (P) and configured to estimate the positioning of the apparatus by processing data in said GNSS signals (D) received from satellites visible in said plurality of satellites (S), called positioning estimate also including a set of positioning aid quantities (xj, yj, zj, hj), called geospatial positioning devices (U) also including respective wireless communication means (T) to operate as a peer in a wireless communication network peer-to-peer (W) and exchange wireless data with one or more other peers (Ua) of said peer-to-peer (W) network, characterized by the fact that one or more of said positioning devices (Uu), peer in said wireless network (W) is configured to operate in an assisted mode to receive wireless data from one or more other peer devices (Ua) of said wireless network (W) which include values of positioning aid quantities (xj, yj, zj, hj), measured at said one or more other peers (Ua) on the basis of the respective received GNSS (D) signals, including measured height values (hj ), said one or more positioning devices (Uu) being also configured to calculate a corresponding estimated height value (haid) by applying a weighted average operation to said measured height values (hj) received in said wireless data received from plus other peers (Ua) and use said haid to estimate the position. 2. System according to claim 1, characterized in that said one or more positioning apparatuses (Uu) are configured to apply weight coefficients (Î ± j) in said weighted average operation calculated as a function of accuracy parameters (βj) received from said one or more other peers (Ua) indicative of the measurement accuracy of the measured height values (hj) received, in particular indicating whether said one or more other peers (Ua) are anchor peers. 3. System according to claim 1, characterized in that said one or more positioning apparatuses (Uu) are configured to apply weight coefficients (Î ± j) in said weighted average operation calculated as a function of parameters (Î · j) dependent on the distance (di) with respect to the peer (Ua) from which the respective measured height value (hj) is received, in particular said distance parameters (Î · j) being calculated by said positioning devices (Uu) by means of of radioranging. 4. System according to claim 1, characterized in that said one or more positioning apparatuses (Uu) are configured to apply weight coefficients (Î ± j) in said weighted average operation calculated as a uniform average with respect to the number (N) of other peers (Ua) from which the measured height values (hj) are received. 5. System according to one or more of claims 1 to 4, characterized by the fact that said one or more positioning devices (Uu) are configured to associate a reliability index (r) to the estimated height value (haid), function inversely proportional to a variance of the measured height values (hj) received from one or more other peers (Ua). 6. System according to claim 5, characterized by the fact that said one or more positioning apparatuses (Uu) are configured to set a variance of the error relative to the height measurement (D h) within a covariance matrix of the measurement errors (R) of the Kalman filter implemented in the receiver (P) of GNSS signals as a function of the reliability index (r), in particular as a function of the inverse square of the reliability index (r) . 7. System according to one of the preceding claims, characterized in that said one or more positioning apparatuses (Uu) are configured to use said estimated height value (haid) to initialize a Kalman filter of the own receiver (P) of GNSS signals . 8. System according to one of the preceding claims, characterized by the fact that said one or more positioning apparatuses (Uu) are configured to implement an iterative aid procedure, which provides for recursively updating the aided height estimate value (haid) and the covariance matrix of the measurement errors (R) of the Kalman filter, in order to improve the estimation of the position. 9. System according to the preceding claim, characterized in that said iterative aid procedure provides for: a) perform an initialization operation of the Kalman filter of your own receiver (P) of GNSS signals comprising the steps of: at an initial time, estimate: an initial position (p0 [0]) of the apparatus (Uu) as a function of position coordinates ({xj, yj, zj}) received from said one or more other peers (Ua), and a corresponding initial misalignment (t [0]) of the receiver clock (P) as a function of said initial position (p0 [0]) and pseudorange measurements available based on the visible satellites, initialize an initial height estimate value (haid [0]) equal to the average of the measured height values (hj) received at the initial time, to initialize a variance of the height measurement error (D h) in the covariance matrix of the measurement errors (R) with a higher value than that obtainable from the available pseudorange measurements, b) perform said recursive update operation comprising the steps of: at a later time (k), calculate a respective position (p0 [k]) and a corresponding clock misalignment (t [k]), using position data ({xj, yj, zj}) received from the visible satellites and a current estimated height value (haid [k]), calculate a GNSS height estimate (<hË † +> <[k]>) based on said position (p0 [k]), calculate a second order moment of the measured height values (hj) with respect to said GNSS height estimate (<hË † +> <[k]>), use said second order moment to update the covariance matrix of the measurement errors (R), calculate a new value of current estimated height (haid [k + 1]) as the weighted average of the GNSS height estimate (<hË † +> <[k]>) at the next instant (k) and the current estimated height value (haid [k]). 10. Geo-spatial positioning method operating in association with a GNSS global satellite navigation system characterized in that it comprises the operations performed by the geo-spatial positioning system according to one of claims 1 to 9. 11. Geo-spatial positioning apparatus configured to operate as a geo-spatial positioning apparatus in assisted mode in the geo-spatial positioning system according to one of claims 1 to 9.