International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Volume XXXIX-B4, 2012
XXII ISPRS Congress, 25 August — 01 September 2012, Melbourne, Australia
SYSTEMATIC BUNDLE ADJUSTMENT OF HRSC IMAGE DATA
J. Bostelmann*, R. Schmidt, C. Heipke
Institute of Photogrammetry and GeoInformation (IPI)
Leibniz Universität Hannover
Nienburger Str.1, D-30167 Hannover, Germany
bostelmann @ipi.uni-hannover.de
Commission IV, WG IV/7
KEY WORDS: Extra-terrestrial, Mapping, Planetary, Matching, Bundle, Adjustment, Global, Analysis
ABSTRACT:
The European Mars Express mission was launched in June 2003 and sent into orbit around Mars. On board the orbiter is the German
High Resolution Stereo Camera (HRSC). This multi-line sensor images the Martian surface with a resolution of up to 12m per pixel
in three dimensions and provides RGB and infra-red color information. The usage of the stereoscopic image information for the
improvement of the observed position and attitude information via bundle adjustment is important to derive high quality 3D surface
models, color orthoimages and other data products. In many cases overlapping image strips of different orbits can be used to form
photogrammetric blocks, thus allowing the simultaneous adjustment of the exterior orientation data. This reduces not only local,
but also regional inconsistencies in the data. With the growing number of HRSC image strips in this ongoing mission, the size and
complexity of potential blocks is increasing. Therefore, a workflow has been built up for the systematic improvement of the exterior
orientation using single orbit strips and regional blocks. For a successful bundle adjustment of blocks using multiple image strips
a sufficient number of tie points in the overlapping area is needed. The number of tie points depends mainly on the geometric and
radiometric quality of the images. This is considered by detailed analysis of the tie point accuracy and distribution. The combination
of methods for image pre-processing, tie point matching, bundle adjustment and evaluation of the results in an automated workflow
allows for all HRSC images a global assessment of the quality and a systematic selection of data for larger blocks.
1 INTRODUCTION With the growing number of HRSC image strips in this ongoing
mission, the size and complexity of potential blocks is increasing
The Mars Express mission conducted by the European Space and a detailed knowledge about the photogrammetric capability
Agency (ESA) is investigating the Red Planet since January 2004. of the HRSC data is needed to assure geometrically stable blocks.
One of the scientific instruments on board the orbiter is the High
Resolution Stereo Camera (HRSC). This multi-line stereo scan-
ner is equipped with 5 panchromatic and 4 color charge-coupled
device (CCD) line detectors, each with 5176 pixels. The configu-
ration of the sensor lines on the focal plane of the camera allows
a stereoscopic image acquisition of the Martian surface (Neukum
et al., 2004). Until March 2012 the HRSC has orbited the planet
10,500 times aiming at a global coverage of image data.
By simultaneously reading out (up to) nine CCD sensor lines,
while the camera points at Mars when reaching the periapsis of
the highly elliptical orbit, long image strips are created. Because
of the different viewing angles in the images of these strips, it
is possible to obtain stereo color data, with a resolution of up to
12m per pixel, depending on the flying height.
To use the HRSC image data for the derivation of digital terrain
models (DTMs) or orthoimages the knowledge about the position
and attitude of the camera is essential. The position is observed
via Doppler measurements, and star trackers control the attitude
of the camera. The combination of these observations is called
the nominal exterior orientation of the camera. In many cases
the quality of the exterior orientation is not accurate enough for a
precise photogrammetric point determination. Therefore, a large
number of automatically determined tie points is used in a bundle
adjustment to improve the accuracy of the exterior orientation and Figure 1: Color coded MOLA DTM with footprints of 21 HRSC
to exploit the full potential of the stereo image data. nadir channel images constituting a photogrammetric block
[n many cases overlapping image strips of different orbits can be We have developed a workflow for a systematic bundle adjust-
used to form photogrammeiric blocks (see Fig. 1), thus allow- ment of the HRSC image data. This workflow for single orbit
ing a more consistent adjustment of the exterior orientation data. strips is described in chapter 2. In chapter 3 the extension of this
* Corresponding author method for multi orbit blocks is described. Results including 2
284
d ux pe que 5 mni ber
ede "Gabe GAS
