Local PD Regional PD Global PD 
Images HRSC HRSC, WAOSS WAOSS 
Datum definition local local or global global 
Block configuration | single strips; small blocks of 
large blocks of many over- | closed block covering the en- 
  
  
  
  
  
  
overlapping or crossing strips lapping strips tire surface 
Computation effort | moderate high very high 
local very high high high 
Accuracy global low moderate high 
  
  
  
Table 1: Local, regional and global point determination (PD) on Mars and their characteristics 
3.2 Local, Regional and Global Point Determina- 
tion 
The point determination (PD) on Mars will be carried out 
at local, regional and global levels (Table 1). 
HRSC will mainly operate in the near periapsis region, so 
that about 10-20% of the Martian surface can be imaged 
by HRSC with a ground pixel size of 12-20 m. The local 
PD is therefore based on HRSC images and implies the 
simultaneous adjustment of several crossing or overlapping 
strips, which will be aquired around the periapsis with a 
nearly constant ground pixel size. 
The regional PD comprises the adjustment of large blocks 
of many overlapping strips and is based on a combined 
evaluation of HRSC and WAOSS images. 
Image sequences for WAOSS are planned for orbital posi- 
tions up to 90° true anomaly. Thus WAOSS images will 
cover the entire planet with 100-1000 m ground pixel size, 
so that a closed block triangulation with complete overlap 
in all three directions may be carried out. 
3.3 Computer Simulations 
Comprehensive computer simulations on local, regional 
and global PD have been performed to obtain a survey 
of the attainable local and global accuracies and to give 
recommendations in the planning phase of the Mars96 mis- 
sion. The results of these simulations are summarized in 
Table 2. 
The local accuracy represents the interior accuracy of PD, 
as the influence of the datum definition is excluded using 
the method of free adjustment. The global accuracy, in 
contrast, stands for the exterior accuracy of PD referring 
to the Mars-fixed reference system. 
  
Local Accuracy | Global Accuracy 
  
pxylm] | pylm] | pgy(m] | pylm] 
Local PD 5 10 300 50 
Regional PD 15 30 100 30 
Global PD 40 40 60 60 
  
  
  
  
  
  
  
Table 2: Attainable planimetric and height accuracies 
(1c) of adjusted object point coordinates for the local, 
regional and global PD on Mars 
The local PD mainly depends on the number, distribu- 
tion and precision of conjugate points and benefits from 
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B3. Vienna 1996 
the high relative accuracy of the orbit and attitude data. 
'The local accuracy can be considerably improved to about 
5m in planimetry and 10 m in height, if the 2 photometric 
channels of HRSC are incorporated into the bundle adjust- 
ment (Fig. 2). 
  
   
  
  
  
   
  
  
   
   
Sigma (2) [m] 
  
Figure 2: Standard deviations of adjusted Z coordinates 
of the object points for HRSC with 3 CCD arrays (above) 
and with 5 CCD arrays (below) 
A large number of simulation runs on regional PD have 
shown that most accurate results can be achieved by com- 
bining HRSC and WAOSS data and by the simultaneous 
block adjustment of multiple overlapping strips with >60% 
side lap and additional crossing strips at the borders of the 
block (Ebner et al. 1994b, Ohlhof 1995). 
Since WAOSS will image the entire planet, a global block 
with complete overlap in all directions may be processed 
under ideal circumstances. Because of the extraordinary 
strength of the closed block and based on the complete im- 
age, orbit, attitude and ground control information, 60 m 
global accuracy in planimetry and height can be achieved. 
In summary, it can be stated that the synergy effect of im- 
age and orbit information is most effective, if many over- 
lapping orbital arcs are processed simultaneously in a block 
with high geometric strength. It can be expected that the 
accuracy of the current ground control network of Mars is 
generally improved by a factor of 10 or more. 
Sigma (2) [m] 
       
  
   
      
   
    
     
     
   
    
      
    
   
  
   
   
  
    
    
   
   
   
    
   
   
     
     
   
    
     
   
    
     
   
   
   
    
3.4 
  
In cas 
Mars 
the M 
frame 
and « 
frame 
radio 
rotatic 
eters 
The N 
where 
Airy-0 
called 
and d. 
the E: 
IAU v 
descril 
equatc 
is desc 
the IA 
throug 
There: 
transf 
equatc 
{Et 
ond 
2 
grd 
Mars 1 
Figure 
of Mar 
J2000 
Neglec 
and W