INFLUENCE ON HEIGHT MEASURE FROM EARTH CURVATURE BASED ON 
SPACEBORNE INSAR 
Zhenghao a ,Tang Xiaotao,Niu Rui,Chen Gang„Liu Zhiming 
a 
Xi’an Research of Surveying and Mapping 
Commission VI, WG VI/4 
KEY WORDS: Interferometric Synthetic Aperture Radar; Earth Curvature; Height Measure 
ABSTRACT: 
It is very different from spacebome InSAR and airborne InSAR because satellite orbit is relatively more higher, the distance 
between satellite subsatellite point and mapping area may be from hundreds to thousands of kilometers. Height measure based on 
spacebome InSAR must eliminate the influence of earth’s curvature, otherwise its error may be higher. But how much is the 
influence of height measure from earth’s curvature to mapping accuracy in spacebome InSAR ? we have not read relative reports. In 
this paper, that is analyzed in detail, and the conclusions are drawn: (D Height measure based on spacebome InSAR must eliminate 
the influence of earth’s curvature and its precision is much higher in that way. ©The error from earth spheroid is well-regulated, 
and may be corrected. (3) According to the height accuracy specifications, in a definite range, the earth’s surface can be taken as flat 
in some area. 
It is applicable to airborne InSAR height measurement that the b -Semiminor axis of ellipse 
earth surface is considered as the plane.But satellite orbit e -First eccentricity of ellipse 
altitude is heigher to spomebome InSAR system, the distance 
between subsatellite point and the mapping area is hundreds of Jt is obvious that R is interrelated with latitude, and it adds 
kilometers, the ellipsoid effect will be taken into along with B’s increase, 
account,ortherwise the height error will be brought. But how 
much influence does the earth ellipsoid cause on mapping Variation is shown as chart 1. 
accuracy , the relative reports do not be viewed. In the paper 
this problem is analysed and discussed in detail. Z 77 explanation 
1. INTRODUCTION 
Where 
N 
InSAR is a new active microwave technology with the 
development and the gradual matureness on the basis of SAR. 
According with the difference of remote sensing platform it is 
divided into spomebome InSAR system(spacecraft as platform ) 
and airborne InSAR system ( aerial aerocraft as platform ) . 
According with the requirement of correlation and the theory 
of InSAR measurement , two kind of spomebome InSAR 
system is mainly defined as follows: :the one is the InSAR 
system on the basis of single satellite platform with two 
antennas ;the other is the InSAR system based on satellite 
formation which is nowadays the developful direction of the 
technology of spomebome InSAR ,and is the hotspot in the 
InSAR research. 
E 
E' 
picture 1 : the earth's ellipsoid 
a -Semimajor axis of ellipse 
2. THE EARTH'S MEAN REDIUS OF CURVATURE 
On Equator , R is less 
than equatorial radius 
a. 
In the practical engineering application, according to the 
accuracy specifications in height survey, to a definite extent, it 
is proper to take ellipsoidal surface as spherical surface with 
5 = 0° 
0° < 5 < 90° 
5 = 90° 
R 
appropriate radius and to take mean value of all direction A 
across some point on the ground as the spherical radius. 
On vertex, R is more 
The spherical radius is the mean redius of curvature R. 
chart 1 : The earth's mean redius of curvature Variation