inbul 2004
' and with
1 RPCs as
an affinity
rection (2
1dividually
significant
ustment. If
of missing
ken out of
RMSY
0.98 m
0.86 m
0.82 m
0.80 m
| points of
key
ation with
ry similar.
rection. In
I. The root
ons is just
International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B1. Istanbul 2004
the Saudi Arabia scene, based on 20 control points with
differences in the elevation up to 338m, the azimuth has
changed 2.0°, reducing the root mean square differences from
1.39m to 1.25m. In another area in Turkey the RMS-values of
two scenes have not been improved with the nominal collection
elevation and azimuth as unknown, but the 6 affinity parameters
have been significant and required.
RMSX RMSY
CORIKON, 8 unknowns (affine + 1.45 m 0.97 m
view direction)
CORIKON, 6 unknowns (affine) 1.51 m 1.00 m
CORIKON, 2 unknowns (shift X, Y) 1.61 m 1.09 m
CORIKON, only terrain correction 2.3] m 4.04 m
Table 2. root mean square discrepancies at 33 control points of
I
IKONOS orientation, New Jersey pixel size Im
In the case of the New Jersey data set the program CORIKON
has removed the nominal collection elevation and azimuth as
not required from the adjustment. This decision is based on a
Student test and it takes also care about correlations of the
unknowns. Also an affinity transformation of the terrain
corrected IKONOS positions to the control points has had a
limited influence, only a shift in X and Y was required. With
just the terrain correction, the result is mainly depending upon
the direct sensor orientation which is causing a shift in X of
1.7m and in Y 3.9m. In several countries the accuracy of the
direct sensor orientation is quite better than the problems with
the datum of the national coordinate system, requiring a fit to
the actual used coordinate system at least by a shift in X and Y.
3.2 QuickBird
of the terrain corrected scene positions to control points) was
not much better like an adjustment with just the 3 significant
unknowns (shift in X and Y together with nadir). Without an
improvement of the nadir direction the discrepancies have been
the same, so in addition to the relief displacement just a shift in
X and Y was required, that means by theory only one control
point could be used. The shift values of 77.7m for X and 9.2m
for Y do present more the datum problems of the national net
than the accuracy of the direct sensor orientation. The
rectification to the GTOPO30-DEM is reducing the height
differences between the actual terrain surface and the reference
plain. This has the negative effect of a poor convergence of an
adjustment with the view direction, but it is still possible to
improve the view direction. On the other hand an improvement
of the view direction has only limited influence caused by the
smaller differences in height between the actual DEM and the
GTOPO30-DEM.
3.3 SPOT
RMSX RMSZ
CORIKON 8 unknowns (affine + 4.88 m 3.51.m
view direction) 5.40m 4.4] m
CORIKON 3 unknowns (shift X, Y, 6.27 m 4.05 m
nadir) 6.72 m 4.38 m
CORIKON 2 unknowns (shift X,Y) 14.97 m 15.29 m
24.99 m 21.78 m
Table 4. root mean square discrepancies at 39 control points of
2 SPOT S-scenes in Zonguldak pixel size 5m
RMSX RMSZ
CORIKON 8 unknowns (affine + 0.58 m 1.27 m
view direction)
onding to
nowns
RIKON 8
e, so with
zimuth has
uracy. The
nge of the
significant
collection
ificant but
he affinity
out of the
ies at the
1 has been
er areas. In
CORIKON 3 unknowns (shift X, Y, 0.58 m 1.36 m
nadir)
CORIKON 2 unknowns (shift X,Y) 0.58 m 1.36 m
Table 3. root mean square discrepancies at 45 control points of
the QuickBird Standard image Saudi Arabia
pixel size 0.61m
The geometric situation of QuickBird OrthoReady images is
exactly the same like for IKONOS Geo. From QuickBird with
the Basic Imagery also the original data only corrected by the
internal calibration are available together with the full sensor
information, but a full scene has to be bought. With QuickBird
Basic images a standard deviation of 388 control points of
SX=0.55m and SY=0.64m corresponding to approximately 1.0
pixel has been reached (Passini, Jacobsen 2004). This accuracy
is usually limited by the identification and the ground
coordinate accuracy of the control points. This accuracy of |
pixel is an operational accuracy which can be reached with
most of the space sensors. It is totally sufficient because the
registration of object elements is in most cases limited by the
object definition itself.
In an area in Saudi Arabia the control point definition in the
images and the ground coordinate accuracy was not so good, so
only an RMSX of 0.58m and an RMSY of 1.27m has been
reached in the QuickBird Standard image. This is still sufficient
for operational applications. The orientation with 8 unknowns
(azimuth and elevation together with an affinity transformation
SPOT scenes are available as original sensor images just
improved by the internal calibration as level 1A and as rectified
images, the level 1B. The level 1B-product is more close to the
map geometry, but it has lost the original geometric relation.
The average of the root mean square discrepancies (RMS) at the
control points of 2 level 1B-orientations in the area of
Zonguldak is with 4.6m below the pixel size of 5m. Such an
operational accuracy will be reached also with the level 1A-
scenes. So the reconstruction of the imaging geometry with
program CORIKON does not lead to a loss of accuracy in
relation to level 1A-scenes like sometimes reported and it is
also not necessary to reconstruct the original image geometry.
With just the shift parameters and a correction of the nadir
angle with 5.47m the average RMS values have been raised just
from 0.9 to 1.1 pixels, but without an improvement of the nadir
angle the result could not be accepted.
3.4 IRS-1C
RMSX RMSZ
CORIKON $8 unknowns (affine + 9.55 m 7.04 m
view direction)
CORIKON 3 unknowns (shift X, Y, 9.40 m 7.17m
nadir)
CORIKON 2 unknowns (shift X,Y) 10.53 m 8.50m
Table 5. root mean square discrepancies at 44 control points of
an IRS-1C-scene in Zonguldak — pixel size-5.8m
Like SPOT, also for IRS-1C the original (level 1A) and the
rectified (level 1B) scenes are available. For nadir images IRS-
IC has a pixel size of 5.8m on the ground. With just a nadir
angle of 2° the available scene in the area of Zonguldak is close
to this. The image quality was not optimal - this may be caused
