The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences. Vol. XXXVII. Part B4. Beijing 2008 
as the reference surface during noise reduction, the UCL DTM 
matched well with the MOLA DTM in most of the cases. 
Another finding was that there was a disparity between the 
DLR V50 DTM and the MOLA DTM. Referring to the profile 
between hi022 and h0103 (Figure 7, bottom), this kind of 
difference occurred in the area of h0103. The initial 
investigation revealed this was due to poor coverage of 
intersection points in DLR V50 DTM (Figure 6, line #3 
outlined in DLR V50 DTM). Although the point shortage also 
occurred in the UCL DTM (Figure 6, line #3 outlined in UCL 
DTM), this issue was improved due to the implementation of 
noise reduction. 
6. SUMMARY 
The positive results demonstrate that a solution for automated 
noise reduction can be an efficient method for refining Mars 
DTMs produced from HRSC stereo imagery. Moreover, it is of 
great potential to decrease the discontinuity between adjacent 
DTMs. Due to these advantages, the proposed method will be 
applied before performing geomorphological analysis and 
geological investigations of Martian surface. It is interesting to 
note that most of the errors detected were along the edges of the 
orbital strips. The reasons for this are unclear but might have 
something to do with errors in the image re-sampling to level 3. 
ACKNOWLEDGEMENT 
The authors would like to acknowledge Prof. Jon Mills and Dr. 
Pauline Miller at Newcastle University for their support of 
3DSurf program. The authors also would like to thank the 
assistance from HRSC-CoI team, especially the PI, Prof. 
Gerhard Neukum. STFC under grant PP/E002366/1 supported 
this study. 
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