DESC:TECHNICAL FIELD
[0001] The present invention relates generally to radar technology . The invention, more particularly, relates to computing target height using three dimensional (3D) primary radar measurements consisting of stacked elevation beams.

BACKGROUND
[0002] The modern 3D radars measure the target range, azimuth, and elevation with respect to the radar to precisely locate the target position in 3D surveillance region. To locate the target position in a global coordinate system the location of radar and the target height with respect to mean sea level (MSL) are required. The target height is not a direct measurable parameter if elevation angle is embedded in channel and sub channel information in 3D Primary radar. The accuracy of target elevation and range are related to the accuracy of computed target height.
[0003] In an 3D radar finding the target height in with stacked elevation beams remains a technical challenge and often iterative computing target elevation automatically using associated radar measurement are suggested. Furthermore, the prior approaches are mostly concerned with improving the elevation angle computation using the hardware circuitry. Furthermore, the prior approaches assumes that the elevation angle is directly obtained as a measured angular value.
[0004] US patent 3049702, titled "Single target height indicator" discloses a single target height indicator suitable for stacked beam radar application. There are two displays one for range and azimuth the other one is for range and height. Single operator can determine the height of a preselected target. This invention relates to a height computing hardware circuitry for distinguishing more than one target appearing at same range and azimuth but with different elevation angles. A method to improve the elevation angle computation is also described in this document using an improved hardware circuitry at the logarithmic receiver.
[0005] US patent US 3070795, titled "Elevation angle computer for stacked beam height finding radar system", relates to the improvements in target elevation angle computer. Even though theoretically the target elevation angle can be obtained from upper and lower beam axes there are practical difficulties. These difficulties are primarily due to the equipment’s used for computing the elevation angle.
[0006] US 4649389, titled "Stacked beam radar and target height measurement extractor especially for use therein", discloses computation of target elevation is computed in the invention from a set of echo information received corresponding to a range cell in which target is present for a mono-pulse radar. Target height is computed from the elevation angle and the computed range measurement set. The target height h is computed as,

wherein R is target range,

However, the invention assumes that the elevation angular information such as cross over angle, angular deviation from cross over are known.
[0007] US 7038615 B2, titled "Efficient technique for estimating elevation angle when using a broad beam for search in radar", describes a method to determine target elevation during a radar search in which target range is computed. Based on the target range, consecutive beams are transmitted in elevation angles. The time multiplexed beams look for target and report back the elevation. These pulses are defocused beams. The defocusing increases with degree of elevation angle being increased. The defocusing is needed in order to efficiently cover the elevation uncertainty angle. Once the target is detected using the defocused beam then the focused beam is used to get the highly accurate elevation angle.
[0008] US 7880668B1, titled "Automated radar elevation angle configuration", discloses the elevation angle of the land based radar system is configured using terrain elevation data of the scan region. The method comprises of dividing the scan region into grid of blocks that are visible and not visible to the radar system. The optimal elevation angle is determined by maximizing the number of visible blocks in the scan region. The method disclosed in the patent assumes that the elevation angle is known accurately by the radar.
[0009] Indian Patent Application 201841012116, titled "System and Method to Obtain Elevation Angle of a Target", discloses elevation angle is computed from stacked elevation beam index settings referred as channel and sub channel numbers. The application also discloses This prior art describes the methodology of computing elevation angle mapped to channel indexes using recorded data. This is not adaptable to following changes like atmospheric changes, radar calibrations, etc., as standalone lookup table is generated from recorded data.
[0010] However, none of the above documents discuss improving the elevation angle computation using the digital data. The documents also fail to provide a stacked-beam locator system that uses stable and reliable beam switching mechanism to accurately determine target elevation and eliminate the errors due to minor lobes of the antenna and also to obtain a single effective elevation angle voltage. There is also a requirement to provide a more robust, overcome time complexity involved in collecting valid recorded data and also avoids repeated computation of standalone methodology for any changes in the system.
[0011] There is still a need of an invention which solves the above defined problems and provides a method and a system obtain elevation angle using associated radar measurements.

BRIEF DESCRIPTION OF ACCOMPANYING DRAWINGS
[0012] The detailed description is described with reference to the accompanying figures. In the figures, the left-most digit(s) of a reference number identifies the figure in which the reference number first appears. The same numbers are used throughout the drawings to reference like features and modules.
[0013] Figure 1 illustrates a flow chart showing flow diagram of Automatic Update of Elevation angle lookup table, according to an exemplary implementation of the present invention.
[0014] Figure 2 illustrates a flow chart for a method to obtain elevation angle using IFF information, according to an exemplary implementation of the present invention.
[0015] Figure 3 illustrates a flow chart for identification and removal of outlier data, according to an exemplary implementation of the present invention.
[0016] Figure 4 illustrates a flow chart for an automatic methodology to update the Elevation angle lookup table, according to an exemplary implementation of the present invention.
[0017] Figure 5 illustrates a flow chart for adaptation step of Figure 1, according to an exemplary implementation of the present invention.
[0018] Figure 6 illustrates a flow chart for data flow, according to an exemplary implementation of the present invention.
[0019] Figure 7 illustrates an example of an Elevation Lookup table, according to an exemplary implementation of the present invention.
[0020] Figure 8 illustrates a flowchart to identify and reporting rogue radar data, according to an exemplary implementation of the present invention.
[0021] Figure 9 illustrates a flowchart for validating the quality of Automatic Elevation Lookup table using a Figure of Merit calculation, according to an exemplary implementation of the present invention.
[0022] It should be appreciated by those skilled in the art that any block diagrams herein represent conceptual views of illustrative methods embodying the principles of the present invention. Similarly, it will be appreciated that any flow charts, flow diagrams, and the like represent various processes which may be substantially represented in computer readable medium and so executed by a computer or processor, whether or not such computer or processor is explicitly shown.

SUMMARY OF THE INVENTION
[0023] This summary is provided to introduce concepts of the present invention. This summary is neither intended to identify essential features of the present invention nor is it intended for use in determining or limiting the scope of the present invention.
[0024] In one embodiment, A method of obtaining elevation angle of a target, the method comprising: receiving, radar data from one or more radars; checking, whether an associated plot is available for the received radar data; obtaining, an elevation angle, for the said received radar data, if the associated plot is available; validating , whether the obtained elevation angle is an outlier plot, if valid, automatically updating a lookup table with the obtained elevation angle and providing quality measure of computed lookup table; if invalid, adapting and storing parameters.
[0025] In one aspect, obtaining elevation angle for the said received radar data, comprises: computing, Identification Friend or Foe (IFF) height from Mode C data received from a secondary radar of the one or more radars, validating whether received IFF height is correct; and if valid, computing, elevation angle from one or more parameters selected from range of target, radius of earth and height of an antenna; if invalid, receive new radar data.
[0026] In another aspect, validating whether the obtained elevation angle is an outlier plot, comprises: fetching mean and variance associated with range and Channel Index of a radar from the received radar data; computing, difference between the current elevation angle and the obtained elevation angle; checking whether the difference is beyond 3 sigma value and validating, whether the received elevation angle is an outlier plot based on the difference.
[0027] In another aspect, the stored parameters are used to identify rogue behaviour of the radar.
[0028] In another aspect, the adapting and storing parameters, comprises: calculating mean difference using mean and variance associated with obtained elevation angle; checking whether the calculated mean difference is beyond 3 sigma value; if the mean difference is more than 3 sigma: incrementing a double rejection count; checking whether the double rejection count is more than a second threshold, updating inconsistency count to validate rogue behavior of radar, where mean of adaptive database is reinitialized with current double rejected sample, receive new radar data; if the mean difference is not beyond than 3 sigma: updating mean and variance; incrementing the reject count and reset double reject count to zero; checking whether if the reject count is greater than a first threshold; and storing the mean and variance for ensuring adaptability.
[0029] In another aspect, the stored parameters are utilized to adapt the radar to cope up for atmospheric variations, wear and tear maintenance, change of tilt angle of antenna, radar calibration changes.
[0030] In another aspect, the method includes identify rogue behavior of a radar, comprising: comparing the inconsistency count with a third threshold; and if inconsistency count is more than a third threshold indicate that the radar is rogue; if inconsistency count is less than a third threshold receive new radar data.
[0031] In another aspect, the validating the quality of an Automatic Elevation Lookup table, the method comprising: calculating an acceptance count and a rejection count to calculate a confidence matrix; computing enrichment of lookup table using confidence matrix; computing figure of merit using confidence matrix; and display the quality of the Automatic Elevation Lookup table.
[0032] In another aspect of the invention, a system to obtain elevation angle for a target, is disclosed. The system comprises: one or more radars configured to provide radar data; a first storage device to store calculated mean and variance data; a second storage device to store adapted data; a processing unit configured to: receive, radar data from one or more radars; check, whether an associated plot is available for the received radar data; obtain, an elevation angle, for the said received radar data, if the associated plot is available; validate, whether the obtained elevation angle is an outlier plot,if valid, automatically update a lookup table with the obtained elevation angle and store the updated lookup table; if invalid, adapt and store parameters.

DETAILED DESCRIPTION
[0033] The various embodiments of the present invention describe about a method and system to obtain Elevation angle from elevation channel and sub-channel numbers using associated radar measurements.
[0034] In the following description, for purpose of explanation, specific details are set forth in order to provide an understanding of the present invention. It will be apparent, however, to one skilled in the art that the present invention may be practiced without these details. One skilled in the art will recognize that embodiments of the present invention, some of which are described below, may be incorporated into a number of systems.
[0035] However, the systems and methods are not limited to the specific embodiments described herein. Further, structures and devices shown in the figures are illustrative of exemplary embodiments of the presently invention and are meant to avoid obscuring of the presently invention.
[0036] It should be noted that the description merely illustrates the principles of the present invention. It will thus be appreciated that those skilled in the art will be able to devise various arrangements that, although not explicitly described herein, embody the principles of the present invention. Furthermore, all examples recited herein are principally intended expressly to be only for explanatory purposes to help the reader in understanding the principles of the invention and the concepts contributed by the inventor to furthering the art and are to be construed as being without limitation to such specifically recited examples and conditions. Moreover, all statements herein reciting principles, aspects, and embodiments of the invention, as well as specific examples thereof, are intended to encompass equivalents thereof.
[0037] This invention relates to a method of computing target height using three
dimensional (3D) primary radar measurements consisting of stacked elevation beams.
[0038] The present invention also discloses refining elevation angle automatically using associated measurement. The elevation angle is important to localize a target in three dimensional space, it helps in association in tracking domain. The method detailed in this invention is about obtaining the elevation angle used for computing target height from elevation channel and sub-channel numbers using combined primary and secondary radar measurements for a track while scan radar. The advantage is the capability to adapt and correct the elevation angles, hence it is not vulnerable against atmospheric variations and radar calibrations.
[0039] The method and system disclosed here is about obtaining and refining the angular elevation values automatically for a given channel and sub channel number corresponding to a stacked elevation beam. The system disclosed here obtains the angular elevation values automatically from the live radar measurement data containing both primary and secondary radar measurements. The secondary radar measurements contain the target height as a measured quantity and the primary radar measurement contains the channel and sub channel numbers along with range. The channel and sub channel numbers are uniquely represented in the invention as Channel Index (CI). For ‘C’ number channels and ‘S’ number of sub channels the CI varies from 1 to N (N = C*S). Using the range and the height information from measurements, the elevation angle is computed, this elevation angle is checked for validity, valid elevation angle will be used to refine existing values stored against the channel and sub channel index in Elevation angle lookup table. This automatic lookup table is used to obtain the elevation angle in the event of 3D surveillance using primary radar alone.
[0040] The disclosed mechanism, make use of the associated measurements to compute the height of targets. An associated measurement (plot) contains the cumulative information of the target data reported by secondary radar and primary radar. The primary radar reports known as primary plots consists of target range (which is the slant range, and, in this invention, it is referred as range), azimuth and embedded information of elevation angle in channel and sub-channel numbers. The associated plot consists of range, azimuth, channel number, sub-channel number and barometric height of target. The barometric height of target is obtained from secondary radar and in this invention, it is referred as secondary height. Thus, the method maps the information communicated by a target to the channel and subchannel number, resulting in the elevation angle of the target. The elevation angle is populated in the form of look-up table consisting of rows referring to range of the target and columns referring to channel index(CI ranging from 1 to N), the number of channels are ‘C’, and each channel is divided into be ‘S’ sub-channels.

[0041] By performing the method steps as disclosed earlier, outlier identification and rejection can be performed, automatic computation of elevation angle corresponding to given channel Sub channel values and range in lookup table is performed, adaptability to changes like atmospheric variations, wear, and tear maintenance of radar(change in tilt angle or elevation beam pattern) is achieved, identification of erroneous behavior of sensor and feedback mechanism for the operator for necessary action to carry out and quality measure of lookup table is also achieved.
[0042] In this invention, a method to compute elevation angle in primary 3D radar with stacked elevation beams using live streaming associated plot data is disclosed. The elevation angle using IFF information is obtained. Then, outlier data identification and rejection is performed. Then, automatic update of elevation angle lookup table of size M*N is performed, where M corresponds to range quanta and N corresponds to channel index. Then adaptation to changes by maintaining rejected samples in adaptive database is then performed. Then, invalid identification and re-initiating the parameters in adaptive database using double rejection count. Then, valid identification and replacing the same in accepted database using rejected count logic is performed. Then, identification and reporting of rogue behaviour of radar, is performed. Then, quality measure of computed elevation lookup table is performed.
[0043] In one embodiment, identification of Outlier data using statistical threshold is performed, and only valid data are passed on to update mean, variance, and count of corresponding cell in total size of elevation lookup table, is performed.
[0044] In one embodiment, a method to compute mean and variance using live streaming data and updating for each cell, is disclosed.
[0045] In one embodiment, a method to maintain adaptive database using rejected samples for coping up the changes like atmospheric variations, wear, and tear maintenance of radar, change of tilt angle of antenna, Radar Calibration changes, and changes in altitude of the antenna, is disclosed.
[0046] In one embodiment, a method to adapt the elevation look up table for the changes occurred in the radar environment by replacing the values in the lookup table cell, is performed.
[0047] In one embodiment, method to identify and remove inconsistent data from adaptive data base using double reject count is performed. This method is a check for identifying and removing the inconsistent data.
[0048] In one embodiment, method to identify rogue behaviour of the radar and feedback to the external world using inconsistency count, is performed.
[0049] In one embodiment, a method to provide the Quality measure of the computed elevation lookup table is performed.
[0050] In one embodiment, the method disclosed is adaptable to changes in antenna location parameters.
[0051] In one embodiment, the abrupt changes in the elevation table due to aforementioned changes are recorded and provided as a feedback to the user.
[0052] Figure 1 illustrates a method for automatic Update of Elevation angle lookup table. At step 101, the data from the radar is received at a Data Reception module. At step 102, the radar data is checked for associated plot, if there is an associated plot the control moves to step 104, where elevation angle is obtained. If there is no associated plot, the control passes to step 103, where data is discarded. At step 105, the obtained elevation angle is checked whether it is outlier or valid data. If the data is an outlier data, the control moves to step 106. The steps performed at step 106, is explained with Figure 6. Alternatively, the control moves to step 107, where the valid data is used to update lookup table. At step 108, the updated lookup table, mean and variance of respective cells are stored in Storage 1 and at step 109, adaptive parameters will be stored and fetched.
[0053] Figure 2 discloses a method to obtain Elevation angle using IFF information. At step 201, an IFF Height from Mode C is carried. At step 202, the computed IFF height is checked for validity, if the computed IFF height is valid, then control moves to step 205 where the Elevation angle is computed otherwise it will be rejected and new data will be received from a main database 204(101). Alternatively, at step 203, data is received.
[0054] Figure 3 discloses a flowchart for identification and removal of outlier data. At step 301, an absolute difference with obtained elevation angle is calculated mean difference is calculated for existing mean and variance of a corresponding cell received from step 302. At step 304, the computed mean difference is compared with 3 sigma of corresponding cell (element in lookup table Fig. 7 consisting of total M x N cells). The control flows back to flow chart of Figure 1, where actions taken for yes/no are explained.
[0055] Figure 4 illustrates an automatic methodology to update the elevation angle lookup table. At step 403, updated variance is computed. At step 404, Updated Mean is computed, and all required details will be fetched from Storage 1 as indicated in step 401 and at step 402, weights are calculated. The updated details will be stored in in Storage 1. The mathematical formulae for each of these steps are discussed in detail below.
[0056] Figure 5 illustrates a flow chart for adaptation step 106 of Figure 1. At step 502, mean and variance details for corresponding cell is fetched from storage 2 and mean difference is calculated. At step 503, the obtained mean difference is compared with 3 sigma, if yes, the control passes to step 504, where double rejection count is incremented. Alternatively, the control passes to step 505, where the data is updated for adaptive database. At step 509, the incremented double rejection is compared with threshold 2 (TH2), if the value is yes, the control moves to step 506, inconsistency count is incremented, where mean of adaptive database is reinitialized with current double rejected sample, variance of adaptive database is reset to zero and inconsistency count is incremented and then stored at storage 2. At step 510, new data is received. At step 505, after updating mean and variance of adaptive database reject count is incremented and at step 507 double reject count is reset to 0. At step 508, the incremented reject count is compared with threshold 1 (TH1 say 30 samples) if yes, control moves to step 512, the mean and variance of accepted database in storage 1 512(Fig.1 108) is replaced with mean and variance of adaptive database and at step 511, inconsistency count is reset to zero. At step 510, this process will accommodate adaptability of look up table for aforementioned changes, otherwise new data will be received.
[0057] Fig.6 illustrates a flow chart for data flow. At step 601, the valid input data received is used for updating mean, variance, and count of size lookup table(M* N). At step 602, the rejected samples are used to update mean, variance, and rejection count of adaptive database, if found valid. The adaptive database will be used to adapt to any changes(Atmospheric changes, wear, and tear radar maintenance issues, change in tilt angle, etc.). The rejected samples from adaptive database will increment double reject count, If the consecutive double reject count exceeds threshold 2 (TH2) the adaptive database will be re-initialized otherwise samples will be discarded. At step 603, the parameters stored in accepted database are shown. At step 604, the parameters stored in adaptive database are shown.
[0058] Figure 7 illustrates a model Elevation Lookup table which contains accepted database and adaptive data base of size M*N. Each database contains mean (µ) and variance(s).The count in accepted database referred as Cn, reject count referred as Cr. Adaptive database contains an additional parameter Double reject count (Dn) and Inconsistency check (ICn) for giving out the rogue behaviour of the radar.
[0059] Figure 8 illustrates a method to identify and report of rogue radar behaviour. At step 801, inconsistency count is fetched from storage 2, and at step 802, inconsistency count is compared with threshold 3 (TH3). If the value returned is yes, that means the measurements reported by radar are neither falling in accepted database (measurements are in line with available elevation lookup table) nor adaptive database (elevation lookup table may require to adapt due to changes in radar environment) which conveys that radar is reporting random data and needs to be addressed. The feedback of rogue behaviour of the radar is reported to user for necessary action.
[0060] Figure 9 illustrates a flowchart for validating the quality of Automatic Elevation Lookup table using a Figure of Merit calculation. At step 903, Confidence Matrix is computed by fetching accept count (Cn) (step 901) from Storage 1 and reject count(Cr) (step 902) from Storage 2. At step 904, the Confidence Matrix provides the enrichment of the lookup table that is computed here which is detailed in mathematical aspects, these enrichments provide the data availability of the lookup table considering all the cells. At step 905, the Figure of Merit (FoM) is computed using confidence matrix gives out quality of the elevation table considering all the enriched cells. The FoM greater than threshold 5 (TH5) and enrichment greater than threshold 4 (TH4) it is declared that the table is efficient otherwise additional data for enrichment is required.
[0061] Figure 10 discloses the system to obtain elevation angle for a target. The system comprises a primary radar 1010, a secondary radar 1050, a first storage 1020, a second storage 1030, a processing unit 1040, and a temporary memory 1060. The primary radar 1010 and the secondary radar 1050 provide the data for processing to a processing unit 1040 to perform specific operations. The processing unit, checks, whether an associated plot is available for the received radar data and obtains, an elevation angle, for the said received radar data, if the associated plot is available from the first storage/second storage. The processing unit 1040 then validates, whether the obtained elevation angle is an outlier plot. If valid, the processing unit 1050 automatically updates a lookup table with the obtained elevation angle and stores the obtained elevation angle in the first storage 1020. If invalid, the processing unit 1050 adapts and stores obtained elevation angle in the second storage. The system of figure 10 also is configured to perform the various method steps as to provide an effective and efficient ways to obtain elevation angle using associated radar measurements.
[0062] The following concepts as to the calculations performed and the method steps are explained.
[0063] The accurate calculation of height from radar measurements must consider the effects such as the curvature of the earth, the refractive properties of the atmosphere at various climatic conditions. The assumption of flat earth, above which the height is calculated leads to discrepancy from the actual height. The earth’s radius should also be accounted while calculating height as earth’s shape is assumed to be an oblate spheroid. A spherical model of earth can be close to the actual shape of the earth, which can account for the curvature of earth’s surface. The height computation with spherical geometry of earth is given below:

[0064] To improve the accuracy of height computation refraction of the radar beam along the ray path to the target must be considered. In free space, radio waves travel in straight lines. In the earth's atmosphere, however, electromagnetic waves are bent or refracted. The bending or refracting of radar waves in the atmosphere is caused by the variation with altitude due to change in refractive index, which is defined as the ratio of the velocity of propagation in free space to the velocity in the medium in question. Atmospheric refraction introduces errors in the radar measurement of elevation angle. The classic method of accounting for atmospheric refraction in radar height computation is to replace the actual earth radius by an equivalent earth radius re=kro. The value of the factor k by which the earth's radius must be multiplied in order to plot the ray paths as straight lines is given in below equation (2)

Where dn/dh is the rate of change of refractive index with height. The factor dn/dh depends on temperature, and partial pressure of the atmosphere. Hence, the multiplication factor k varies depending on the region where the radar is deployed.
[0065] The computation of elevation angle is described as to the invention. For the calculation of Elevation angle, ?T the plots obtained from radar is employed. The method disclosed here obtain two kinds of plots viz primary and associated plots.
The barometric height is mapped to unique elevation angle as in equation (3) which is
used to update lookup table (Storage 1 in Fig.1 108).

[0066] The elevation angle obtained is used to update lookup table of size M x N where the number of rows M represents the number of range quanta and the columns N denote the corresponding mapped channel and sub-channel number combination(Channel Index CI). The entries in table represent elevation angle corresponding to a unique combination of channel and sub-channel at the range denoted by the row. The total coverage in range is divided into range quanta ‘q’ (say 1 km each) There can be multiple entries corresponding to a channel and sub-channel number combination each of which pertaining to different targets which are used to for updating the lookup table automatically.
[0067] Mean difference is calculated with equations as shown below.

[0068] The Automatic Methodology disclosed in this invention calculates the parameters of the distribution iteratively. Equation (6) shows updated mean and equation (7) shows updated variance.

Mean(existing) and variance(existing) is fetched from storage 1 (step 108) . The Variance is initialized as 0.03 for all cells in 1st iteration. The Mean(updated) and variance(updated) are stored back to storage 1(step 108).

[0069] Weight is calculated at step 402 as shown below.

[0070] The data rejected from accepted database will be forwarded to adaptive data base, at adaptive database a check will be carried as explained in fig.5 the rejected
samples from adaptive database will be counted as double reject count(Dn). Each
time double reject count crosses the threshold 2 (TH2) then the inconsistency count
(ICn) will be incremented. If for a time period ‘T’ if the inconsistency count exceeds the threshold 3 (TH3) in at least Q% (Q is a configurable parameter and default value is 80%) of enriched cells(M x N) then the measurement reported by radar are found be erroneous and radar could be declared as rogue radar.
[0071] The quality of the lookup table is measured with the following parameters.

[0072] The FoM is quality measure of the lookup table only if the enrichment crosses a threshold 4 (TH4 say above 0.6) and also FoM cross a threshold 5 (TH5 say 0.8) then the quality of the lookup table is ascertained otherwise wait for some more data for enriching the lookup table.
[0073] Threshold 1 (TH1): This parameter is used for taking the decision for replacing the elevation lookup table of accept database with adaptive database for a given cell. Default value is 30.
[0074] Threshold 2 (TH2): This parameter is used to reject/reset the adaptive database (inconsistency check) for a cell. Default value is 5.
[0075] Threshold 3 (TH3): This parameter is used for declaring the randomness/rogue performance of the radar measurements. Default value 10.
[0076] Threshold 4 (TH4): This parameter gives out the quality assurance of the computed elevation table. Default is 0.6
[0077] Threshold 5 (TH5): This parameter gives out the amount of data filled in lookup table. Default value 0.8.
[0078] The foregoing description of the invention has been set merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the substance of the invention may occur to person skilled in the art, the invention should be construed to include everything within the scope of the invention.

,CLAIMS:
1. A method of obtaining elevation angle of a target, the method comprising:
receiving (101), radar data from one or more radars ;
checking (102), whether an associated plot is available for the received radar data;
obtaining (104), an elevation angle, for the said received radar data, if the associated plot is available;
validating (105), whether the obtained elevation angle is an outlier plot,
if valid, automatically updating (107) a lookup table with the obtained elevation angle and providing quality measure of computed lookup table ;
if invalid, adapting (106) and storing parameters (109).

2. The method as claimed in claim 1, wherein obtaining elevation angle for the said received radar data, comprises:
computing (201), Identification Friend or Foe (IFF) height from Mode C data received from a secondary radar of the one or more radars,
validating (202) whether received IFF height is correct; and
if valid, computing (205), elevation angle from one or more parameters selected from range of target, radius of earth and height of an antenna;
if invalid, receive (204) new radar data.

3. The method as claimed in claim 1, wherein validating whether the obtained elevation angle is an outlier plot, comprises:
fetching mean and variance associated with range and Channel Index of a radar from the received radar data;
computing (301), difference between the current elevation angle and the obtained elevation angle;
checking (303,304) whether the difference is beyond 3 sigma value and validating (105), whether the received elevation angle is an outlier plot based on the difference.

4. The method as claimed in claim 1, wherein updating a lookup table with the obtained elevation angle, comprises:
calculating (402) weights based on number of samples obtained for corresponding range and Channel Index of a radar from the received radar data;
computing (403) variance based on calculated weights, obtained elevation angle, mean and variance associated with a current elevation angle from the first storage and storing the computed variance;
computing (404) mean based on calculated weights, obtained elevation angle and mean associated with the current elevation angle and storing the computed mean in the first storage.

5. The method as claimed in claim 1, wherein the stored parameters are used to identify rogue behaviour of the radar.

6. The method as claimed in claim 1, wherein adapting (106) and storing parameters, comprises:
calculating (502) mean difference using mean and variance associated with obtained elevation angle;
checking (503) whether the calculated mean difference is beyond 3 sigma value;
if the mean difference is more than 3 sigma:
incrementing (504) a double rejection count;
checking (509) whether the double rejection count is more than a second threshold,
updating (506) inconsistency count to validate rogue behavior of radar, where mean of adaptive database is reinitialized with current double rejected sample,
receive (510) new radar data;
if the mean difference is not beyond than 3 sigma:
updating (505) mean and variance;
incrementing (507) the reject count and reset double reject count to zero;
checking (508) whether if the reject count is greater than a first threshold; and
storing (511) the mean and variance for ensuring adaptability.

7. The method as claimed in claim 6, wherein the stored parameters are utilized to adapt the radar to cope up for atmospheric variations, wear and tear maintenance, change of tilt angle of antenna, radar calibration changes.

8. The method as claimed in claim 5, wherein the method includes identifying rogue behavior of a radar, comprising:
comparing the inconsistency count with a third threshold; and
if inconsistency count is more than a third threshold indicate that the radar is rogue;
if inconsistency count is less than a third threshold receive new radar data.

9. The method as claimed in claim 1, wherein the method comprises validating the quality of an Automatic Elevation Lookup table, the method comprising:
calculating an acceptance count and a rejection count to calculate a confidence matrix;
computing enrichment of lookup table using confidence matrix;
computing figure of merit using confidence matrix; and display the quality of the Automatic Elevation Lookup table.

10. A system to obtain elevation angle for a target, the system comprising:
one or more radars (1010, 1050) configured to provide radar data;
a first storage device (1020) to store calculated mean and variance data;
a second storage device (1030) to store adapted data;
a processing unit (1050) configured to:
receive, radar data from one or more radars;
check, whether an associated plot is available for the received radar data;
obtain, an elevation angle, for the said received radar data, if the associated plot is available;
validate, whether the obtained elevation angle is an outlier plot,
if valid, automatically update a lookup table with the obtained elevation angle and store the updated lookup table;
if invalid, adapt and store parameters.

11. The system as claimed in claim 10, wherein the processing unit (1050) is configured to obtain, an elevation angle, for the said received radar data, if the associated plot is available, wherein the processor is further configured to:
compute, Identification Friend or Foe (IFF) height from Mode C data received from a secondary radar of one or more radars,
validate whether received IFF height is correct; and
if valid, compute, elevation angle from one or more parameters selected from range of target, radius of earth and height of an antenna;
if invalid, receive new radar data.

12. The system as claimed in claim 10, wherein the processing unit (1050) is configured to validate whether the obtained elevation angle is an outlier plot, the processor is further configured to:
fetch mean and variance associated with range and Channel Index (CI) of a radar from the received radar data and current elevation angle from a first storage;
compute, difference between the current elevation angle and the obtained elevation angle;
check whether the difference is beyond 3 sigma value and
validate, whether the received elevation angle is an outlier plot based on the difference.

13. The system as claimed in claim 10, wherein the processing unit (1050) is configured to update a lookup table with the obtained elevation angle, comprising:
calculate weights based on number of radar data values obtained in corresponding range and Channel Index of a radar of one or more radars;
compute variance based on calculated weights, obtained elevation angle, mean and variance associated with range and Channel Index of radar data value from the first storage and storing the computed variance;
compute mean based on calculated weights, obtained elevation angle and mean associated with range and CI of current radar data and storing the computed mean in the first storage.

14. The system as claimed in claim 10, wherein the processing unit (1050) configured to adapt and store parameters, the processor is configured to :
calculate mean difference using mean and variance associated with obtained data from the second storage;
check whether the calculated mean difference is beyond 3 sigma value;
if the mean difference is more than 3 sigma:
increment a double rejection count;
check whether the double rejection count is more than a second threshold,
update inconsistency count, where mean of adaptive database is reinitialized with current double rejected sample,
receive new radar data;
if the mean difference is not beyond than 3 sigma:
update mean and variance;
increment the reject count and reset double reject count to zero;
check whether if the reject count is greater than a first threshold; and
store mean and variance to the first storage.