In view of the complexity of geodetic line equation and the difficulty of efficient plotting,the formula of the forward and backward solutions of geodetic problem with third flattening n is changed,the accuracy of geodetic azimuth calculation according to the mathematical relationship between normal transversal azimuth and geodetic azimuth is improved,and an equidistant interpolation geodetic line plotting method is proposed.A precision adaptive control model was established by using Mathematica to improve the efficiency and precision of equal spacing interpolation.Using the powerful mapping function of Mathematica,the geodetic line plotting of different map projections under different distances and application scenarios is realized,and the application value of geodetic line plotting is explored.Experimental results show that the method can achieve high efficiency geodetic line drawing of arbitrary length under the condition of controlled accuracy.Geodetic line plotting of different map projections has unique significance in different application scenarios.
The next-generation navigation system is proposed to incorporate Low Earth Orbit(LEO)satellites as an enhancement and backup.The theory and method of integrated Precise Orbit Determination(POD)of high,medium and low orbit satellites using ground station network and spaceborne GNSS receiver data is studied.A high-precision dynamic model and observation model are established,and the integrated POD experiments of navigation satellites and LEO satellites are carried out under the cases of global station and regional stations using real data.The results show that the integrated POD can obtain centimeter-level POD accuracy for both navigation satellites and LEO satellites simultaneously.As a high-dynamic space-based station,the LEO satellites can help improve the POD accuracy of navigation satellites by 20%～90%.
Aiming at the problem of aircraft approach and landing,a design scheme of sequence signal based on JFM7K325T landing equipment is proposed.JFM7K325T is responsible for generating digital signal processing clock and reset,logic control and data preprocessing.Under the synchronization of the clock the landing equipment data signals with different functions are generated according to certain formats.The feasibility of the scheme is verified by experiments.
The passive radar imaging system exploits the opportunity illuminator as its transmitter.The system realized the detection of targets we are interested in by deploying multiple receivers around the target area.Comparing with the traditional radar imaging system,the passive radar imaging system has advantages of low cost,robustness against to deliberate directional inference and strong survivability.Taking account of the various advantages above,wide attention has been attracted from many research organizations.The signal transmitted by the opportunity illuminator is narrow bandwidth which makes the range resolution cell poor.Aiming at solving the problem listed above,the model of the passive radar imaging system is built based on the principle of tomography.Taking account of the sparse distribution of the scatters of the target,a high resolution imaging algorithm is developed based on the compressed sensing.Finally,the influence of the imperfect motion of the moving platform on the received signal is analyzed.The contaminated signal model is reformed.The corresponding compensation method based on the fixed-point iterative method is proposed for improving the performance of the imaging system by correcting phase errors.The theoretical analysis and numerical simulations verify the effectiveness of the method.
The target echo Directing of Arrival(DOA)estimation algorithm based on array signal processing has the characteristics of strong resolution,high estimation accuracy and strong anti-interference ability.These algorithms are also research hotspots in target direction finding.The Multiple Signal Classification(MUSIC)algorithm is one of the DOA estimation algorithms,and the traditional MUSIC algorithm assumes that the target echoes are not correlated with each other,which leads to its application effect being greatly limited.Based on the traditional MUSIC algorithm,the spatial smoothing MUSIC algorithm is used to decoherence the target echo,and the expression for estimating the target DOA and the implementation flow block diagram of the algorithm are derived.The advantages and disadvantages of the algorithm are compared and analyzed based on the numerical simulation results.The MUSIC algorithm has certain advantages in low-DOA,single target multipath problem,multi-target DOA and targets number estimation.
