at
'ol
ck
oh
M
he
on
43
ace
are
ater
> of
rbit
International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B7. Istanbul 2004
error, attitude error, ephemeris error and drift error, the X Yin
formula (1) should be changed as :
X-agta,x-ta»y
y=bo+b,x+by (2)
The rational polynomial coefficients are regarded as constant,
and the error equation of the formula (1) is as follow:
OF, OF. £F,
x
V - [B, 2l E (3)
Bi OB OL CH
| jor, oF, e,
V.
where V -| |
V =
OB OL oH
|l x py 0.0.0
B Y=
7 0.0 0 1 xy
X=[B ài oup
I [ag a a, bo bi by T
Fe = FY
L=
F,- p
There are two kinds of unknown parameters in formula (3),
namely the correction of the image coordinate t and the
correction of the ground coordinate X. After the normal
equation is built up and block adjustment is done, the bias aj
by and the drift a, as! b, 1b, are be calculated. When the strap
length is under 20km, the drift b;! Jb) can be ignored for they
are very small.
2.2 The transformation between WGS-84 system and the
national coordinate system
The datum of satellite is WGS-84 system, but every country or
region owns their geodetic datum. In China, 1954 Beijing
coordinate system used the Karassove ellipsoid, and the 1980
national coordinate system adopted the ellipsoid recommended
by IUGG in 1975. In order to meet the practice application, the
WGS-84 coordinate must be transformed to the national system.
The formula Bushar is used for the transformation between the
coordinate systems(Zhu Huatong, 1986)!
dL XolosIox :
dB |= Al Yy |+B| ey |+CK «a (4)
| dH Z9 £7 qe
Where dL,dB,dH-the coordinate correction between the
systems;
Xo, Y ,Zo-the offset parameters;
£x,€,,£, “the rotate parameters;
K-the scale factor;
da,da =the correction of the ellipsoid parameters
between the systems;
A,B,C,D-the correspond transform matrix.
When the coordinates of certain system were transformed, they
can be projected to the plane coordinate according to a
projection, such as the Guass-Krüger projection. To satisfy the
engineering design and construction in high altitude area, the
coordinate should be further projected to compensate plane of
the surveying area.
2.1,2.2 described the relationship from Ikonos image space to
the object space of ground points in national system.
Contrariwise, the ground coordinate can be transformed to the
image coordinate.
3. THE PRACTICE AND THE RESULT
3.1 The project area
The project area of the Ikonos application is located in the
southeast of the Tibet, P.R. China, a valley near the Himalayas.
It is a mountain area and the terrain undulate sharply. The
average height above sea level is 4000m, the lowest altitude is
2730m, and relative height is over 3000m. The snow covers the
mountaintop all over the years. There is a river across the area
and a road along the river.
There are flourish trees and vegetables in the area. Except the
sloping fields assarted by the farmers, the most area is covered
by originality forest. The height of some trees is over 40m.
Few people lived there, and the most are Tibetans. The life
condition is awful and the civilization and the traffic get more
behind. .
The area of the Ikonos project is a rectangle block. The length
in the east-west is about 35km, and the width in the south-north
is about 20km. The area is covered with 3 stereo Ikonos images
collected in 3 passes. It is very difficult to collect the Ikonos
image for it is rainy and cloudy almost every day. A period of
time has been spent to get the qualified Ikonos products. Some
data of the Ikonos images are listed in table I.
Stereo Pair 1(03/05) 11(07/09) III(12/13)
Image ID 03 05 07 09 12 13
GSD in Cross Scan(m) 0.87 0.92 0.88 0.96 0.90 0.99
GSD in Along Scan(m) 0.90 0.91 0.89 0.95 0.89 0.96
Scan Azimuth(degrees) 0.03 0.03 0.02 0.02 339.97 359.97
Collection Azimuth(degrees) 331.9226 226.5768 318.5048 229.2133 309.4420 232.9035
Collection Elevation(degrees) 71.10912 67.38771 70.68800 63.52693 69.60148 61.80649
Sun Angle Azimuth(degrees) 162.8567 163.1557 165.1714 165.4367 165.3093 165.5509
Sun Angle Elevation(degrees) 45.39864 4545548 39.26270 39.31216 37.07084 37.11749
Acquisition Date(Month-Day) 10-29 10-29 11-20 11-20 12-01 12-01
Table 1 The information of the Ikonos-2 data
1045
