US 11,054,503 B2  
Radar target spherical projection method for maritime formation  
Yi Mao, Nanjing (CN); Yunru Li, Nanjing (CN); Ping Chen, Nanjing (CN); Guan Wang, Nanjing (CN); Daqing Huang, Nanjing (CN); and Bo Wang, Nanjing (CN)  
Assigned to THE 28TH RESEARCH INSTITUTE OF CHINA ELECTRONICS TECHNOLOGY GROUP CORPORATION, Nanjing (CN)  
Appl. No. 16/605,077  
Filed by THE 28th RESEARCH INSTITUTE OF CHINA ELECTRONICS TECHNOLOGY GROUP CORPORATION, Nanjing (CN)  
PCT Filed Sep. 16, 2019, PCT No. PCT/CN2019/105868 § 371(c)(1), (2) Date Oct. 14, 2019, PCT Pub. No. WO2020/057453, PCT Pub. Date Mar. 26, 2020. 

Claims priority of application No. 201811079124.8 (CN), filed on Sep. 17, 2018.  
Prior Publication US 2020/0309907 A1, Oct. 1, 2020  
Int. Cl. G01S 7/41 (2006.01) 
CPC G01S 7/41 (2013.01)  3 Claims 
1. A radar target spherical projection method for generating and using a single integrated picture (SIP) in a maritime formation comprising executing following steps:
step 1, performing a projection modeling of a target at each of a plurality of platforms;
step 2, calculating in the each platform an altitude of the target wherein the calculating comprises a specific process as follows:
substituting D=ρ cos θ, h=ρ sin θ into a spherical projection model of the target, to obtain:
Z(Z+2R)=2(a+R)ρ sin θ+a(a+2R)+ρ^{2}, namely,
converting the above formula as R>>a, R>>Z, to obtain an altitude calculation formula of the target as follows:
step 3, calculating a projection of the target on a radar plane in the each platform;
step 4, calculating the projection of the target on an earth spherical surface in the each platform which comprises a specific process as follows:
step 41, setting
wherein β represents a central angle formed by a target projection point Q on the earth spherical surface and a radar position at a point
is an angle of circumference, d is a side length of a part, tangent to the radar position, of an opposite side of
and supposing that a point P exists, the side length is SP=d;
step 42, substituting h in d=2RD/2R+Z+h+a in the step 41 through the (formula 1), to obtain:
step 43, setting
regarding K_{2 }as a spherical projection coefficient, so that
d=K_{2}·D,
substituting D in d=K_{2}·D above from
D=K_{1}·ρ (formula 2),
to obtain
d=K_{1}·K_{2}·ρ (formula 3);
step 44, approximately substituting a projection point of the target on the earth spherical surface with the point P, and obtaining coordinates P(X_{Q},Y_{Q}) of the spherical projection of the target according to a principle of a same proportion of sides of similar figures, namely:
wherein X_{Q }represents an East coordinate of the projection of the target on the earth spherical surface, and Y_{Q }represents a North coordinate of the projection of the target on the earth spherical surface;
so, calculation formulas of spherical projection coordinates and the altitude of the radar target are as follows:
step 5, collecting obtained projections of the target on the earth spherical surface from multiple platforms for preprocessing radar data and generating a picture; and
step 6, processing radar data including data of spacetime consistency of the target from the multiple platforms, correcting projection errors by calculating data on the altitude, the projection on the earth spherical surface of the target from the multiple platforms, generating the single integrated picture (SIP), and using the SIP for supporting a load control of the platform or a collaborative control over the maritime formation.
