An assessment of surface matching for the automated co-registration of MOLA, HRSC and HiRISE DTMs

Martian topographic data has been collected by various exploration missions over the last decade. These products provide detailed topographic information and are invaluable for scientists to interpret and understand the geological and climate evolution which has occurred on Mars. In order to fully utilise these multi-sensor, multi-resolution and multi-scale Martian topographic products, a co-registration process has been developed which allows co-registration of Digital Terrain Models (DTMs) to be performed to co-align these multiple datasets. Surface matching is the core technique to implement this task and it is here assessed to determine the parameters of the most robust algorithm for DTM co-registration. Once this task was finished, the matching tool was developed accordingly with a decision algorithm. This algorithm was then employed to align DTMs derived from Mars Orbiter Laser Altimeter (MOLA), High Resolution Stereo Camera (HRSC) and High Resolution Imaging Science Experiment (HiRISE). For MOLA and HRSC DTMs, the co-registration was performed directly as the MOLA DTM acted as a reference surface within a bundle adjustment process. DTMs from different versions covering three HRSC orbital strips were used for the assessment process. As a result the mean bias of the height differences of a preliminary version HRSC DTM was significantly reduced from 38.596 m to 2.233 m, when compared against MOLA while the bias of a newer DTM was improved from 1.616 m to 0.161 m after matching. Regarding the co-registration of HiRISE and MOLA DTMs, a hierarchical approach employing a HRSC DTM as an intermediate dataset was assessed. The results demonstrated that the method is feasible and that the three DTMs were co-registered effectively. Due to the success highlighted in this paper, a surface matching tool is recommended to be applied to DTMs derived from multiple sources before these data are further used. Moreover, surface matching can be considered as an additional step of any workflow for Mars DTM creation.