The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences. Vol. XXXVII. Part B4. Beijing 2008 
1038 
nominal ground resolution (m per 
pixel) 
HRSC Orbit 
nadir 
stereo 
photometry 
53250001 
12.5 
25 
50 
53070000 
12.5 
25 
25 
52890000 
12.5 
25 
25 
5271 0000 
12.5 
12.5 
25 
5253 0000 
12.5 
12.5 
25 
52350000 
12.5 
12.5 
25 
Table 1. Nominal ground resolution of the HRSC orbits (only 
panchromatic channels) 
3. METHODS 
This chapter briefly describes the basic photogrammetric 
processes; for more information consult the corresponding 
papers. For a detailed overview of HRSC image processing 
refers to Schölten et al. (2005). 
Chapter 3.1 describes the automatic determination of tie points 
by software provided by the Leibniz Universität Hannover. 
These tie points are used as input in the bundle adjustment (see 
chapter 3.2), provided by the Technische Universität München 
and the Freie Universität Berlin, to improve the exterior 
orientation for single HRSC orbits and for a bundle block 
adjustment with more than one HRSC orbit. These refined 
exterior orientations allows us to adapt the HRSC derived data 
to the global Mars reference system defined by MOLA and will 
be used for the derivation of high resolution DTMs and 
ortho-image mosaics, described in chapter 3.3. 
3.1 Determination of Tie Points 
In order to process large image blocks it is necessary to enhance 
the concept for tie point matching presented in Schmidt et al. 
(2008). It is not reasonable to process the tie point matching in 
all images of the block simultaneously because only 
neighbouring strips overlap. Therefore, the block is divided into 
parts which consist of two neighboring strips respectively. 
Figure 1 shows this concept for a block consisting of three 
single strips. 
entire block 1. partial block 2. partial block 3. partial block 
Figure 1. Concept of partial blocks 
The whole block is divided into the same number of partial 
blocks as the number single strips where each strip once has to 
act as master strip. In case of the block presented in this paper 
six partial block have to be build and processed separately. Note 
that the last strip of the entire block has no partner. More 
information can be found in Schmidt (2008). 
3.2 Bundle adjustment 
The bundle adjustment approach for photogrammetric point 
determination with a three-line camera is a least-squares 
adjustment based on the well known collinearity equations. The 
approach estimates the parameters of the exterior orientation 
only at a few selected image lines, at the so-called orientation 
points. Because of Doppler shift measurements to estimate the 
position of the orbiter there are systematic effects in the 
observed exterior orientation. To model these effects in the 
bundle adjustment additional observation equations for bias 
(offset) and drift have to be introduced. To use the MOLA DTM 
as control information the least squares adjustment has to be 
extended with an additional observation equation for each 
HRSC point. These observations describe a relation between the 
MOLA DTM and these HRSC points. This approach is given in 
more detail in Ebner et al. (2004), Spiegel (2007a), Spiegel 
(2007b) and Schmidt et al. (2008). 
The approach is valid for single orbits as well as for block 
configurations. But, there are differences in operational use 
concerning blunder detection of tie points and concerning 
differences between HRSC points and the MOLA DTM. The 
reason for these differences is that the resolution of the MOLA 
DTM is lower than the accuracy of HRSC points and depends 
on terrain slopes. That circumstance can occur, for example, at 
the rims of craters. Another reason for differences is that the 
MOLA data does not contain small craters in contrast to the 
HRSC data. 
The blunder search for single orbits is carried out in two steps. 
First, blunders of tie points are detected without using the 
MOLA DTM, i.e. only ray intersections are used for this 
investigation. In the second step, the DTM is introduced and the 
HRSC points are registered to the MOLA DTM. During this 
step HRSC points are eliminated that do not fit to the MOLA 
DTM surface. After the two steps, we have an exterior 
orientation for the orbits and a data set of tie points without 
blunders and without big differences between MOLA DTM and 
HRSC points. 
To compute blocks it is necessary to divide the blocks 
temporary into single orbits. With the divided orbits a blunder 
search for single orbits can be arranged (two steps). The 
resulting set of tie points without blunders is used instead of the 
original tie point set for the next steps. In the third step, ray 
intersections of tie point located in the overlapping area of two 
orbits are investigated. The reason for this is to detect blunders 
in HRSC points, that are built from tie points located in two or 
more orbits. The fourth step is to register the remaining HRSC 
points to the MOLA DTM and compute the block adjusted 
exterior orientations. 
3.3 DTM derivation 
Derivation of DTMs and ortho-image mosaics are basically 
performed using software developed at the German Aerospace 
Center (DLR), Berlin and is using the Vicar environment 
developed at JPL. For our DTM derivation, the main processing 
tasks are first a pre-rectification of image data using the global 
MOLA-based DTM, then a leastsquares area-based matching 
between nadir and the other channels (stereo and photometry) in 
a pyramidal approach and finally, DTM raster generation. 
Parameters for the derivation of preliminary DTMs are 
individually adapted to the image quality and to the initial DTM. 
The result is a preliminary HRSC-based DTM which is used for