Page 179 - Radar Technology Encyclopedia

169 error, platform-dependent error, platform-dependent

Platform-dependent error is the error introduced by a mov- the errors caused by the variety of the different external fac-
able platform (e.g., a ship, an aircraft, a spacecraft) in the tors depending on the type of movable platform can be classi-
measurement of the target coordinates. These errors are fied as the errors of nonradar character arising from the linear
caused by a variety of factors: the errors in evaluation of the and angular platform motion in 3D space (including oscillat-
platform location in three-dimensional space by the naviga- ing motion relative to its center of gravity) and the attendant
tion systems (autonomous or external), the errors in evalua- factors (e.g., deformations of the platform), and the errors of
tion of the platform orientation (yaw, pitch, and roll), the the radar-performance character arising from the distortion of
spatial oscillations of the platform relative to its center of radar characteristics due to the platform motion (e.g., distor-
gravity, the dynamic deformations of the platform itself and tion of angle-sensing response due to dynamic antenna defor-
radar antennae because of these oscillations, and so on. All of mation).

Table E6
Platform-Dependent Errors
Coordinate Evaluation formula Source of error

Azimuth, f
æ acos ( cos f+ df) f , – 0 £ f £ p For Df, Dq: errors in orientation
1
1
ç i
Df = ç of reference frame (Fig. E14), e.g.,
,
i i = 12
ç errors in measurement of yaw
£
è 2p acos– ( cos f+ df) f , – p£ f 2p (Da), pitch (Da ), roll (Da);
i
3
2
1
deformations causing angular dis-
placement (Da, Da , Da) etc.
2
1
3
2
(
×
df = sin fDa + cot q sin f) Da – 0.5sin 2fDa ]
×
[
×
1 1 2 3
(
df = e csc q sin h cos fcos b cos– h ) ,q 0 p,¹
2 3 2
Elevation, q Dq = acos ( cos q+ dq) , 0 £ q £ p
–
q
i i
×
×
(
dq = – sin q cos f Da sin+ qDa ) For Df, Dq, DR: errors in origin
2
2
1 2 3
of the location of the reference
e = h R ; b¤ = f – h
1 2 frame (Fig. E15); e.g., deformations
causing linear displacements; errors
in platform location measurement,
and so forth.
2
[
–
dq = e 0.5sin ( 2q ) sin h cos b ( sin q) cos h ]
2 3 3
Range, R DR = – h sin qcos b sin h cos+ qcos h )
(
1 3 3
Figure E14 Figure E15
z
z
Target
R
h 2
Da 3
q
h
f 1
y y
Da 1
Da 2 h
x x 3