Kaichang Di

Rational Functions and Potential for Rigorous Sensor Model Recovery

achieve a higher accuracy and to be effective for implementaRational functions (RFs) have been applied in photogrammetry tion. Madani (1999) discussed advantages and disadvantages of and remote sensing to represent the transformation between RFs compared with rigorous sensor models. He tested the accuthe image space and object space whenever the rigorous model racy of the RF solution using 12 SPOT Level 1A scenes of the is made unavailable intentionally or unintentionally. It at- Winchester area in Virginia. Using two stereo image pairs with tracts more attention now because Ikonos high-resolution 50 ground (control/pass) points, the RMS error of the planimetimages are being released to users with only RF coefficients. ric coordinates estimated from the differences between the This paper briefly introduces the RF for photogrammetric known and computed ground coordinates is 0.18 m. The RMS processing. Equations of space intersection with upward RF error of the Z coordinate is about 10 m. It is concluded that the are derived. The computational experimental result with one- RF expressed the SPOT scenes very well and that properly meter resolution Ikonos Geo stereo images and other airborne selected RFs can be used in operations of digital photogramdata verified the accuracy of the upward RF-based space metric systems. Tao and Hu (2000; 2001b) and Tao et al. (2000) intersection. We demonstrated different ways to improve the gave a least-squares solution for RF parameter generation and geopositioning accuracy of Ikonos Geo stereo imagery with assessed the fitting accuracy using simulated DEM data, a SPOT ground control points by either refining the vendor-provided scene, and an aerial image. In their comprehensive investigaIkonos RF coefficients or refining the RF-derived ground tion, various scenarios with different polynomial orders and coordinates. The accuracy of 3D ground point determination different forms of the denominators were tested and compared. was improved to 1 to 2 meters after the refinement. Finally, It was found that RFs are sensitive to the distribution of control we showed the potential for recovering sensor models of a points (CPs). If CPs are well distributed, RFs normally perform frame image and a linear array image from the RF. much better than regular polynomials (no denominator). Hu and Tao (2001) proposed two methods to update solutions of

Initial Results of Rover Localization and Topographic Mapping for the 2003 Mars Exploration Rover Mission

This paper presents the initial results of lander and rover localization and topographic mapping of the MER 2003 mission (by Sol 225 for Spirit and Sol 206 for Opportunity). The Spirit rover has traversed a distance of 3.2 km (actual distance traveled instead of odometry) and Opportunity at 1.2 km. We localized the landers in the Gusev Crater and on the Meridiani Planum using two-way Doppler radio positioning technology and cartographic triangulations through landmarks visible in both orbital and ground images. Additional high-resolution orbital images were taken to verify the determined lander positions. Visual odometry and bundleadjustment technologies were applied to overcome wheel slippages, azimuthal angle drift and other navigation errors (as large as 21 percent). We generated timely topographic products including 68 orthophoto maps and 3D Digital Terrain Models, eight horizontal rover traverse maps, vertical traverse profiles up to Sol 214 for Spirit and Sol 62 for

Rover Localization and Landing Site Mapping Technology for the 2003 Mars Exploration Rover Mission

SUMMARY The above introduced the technology and experiments for rover localization and landing sitemapping in the 2003 MER mission. At first, Mars global and landing site local reference systemsare elucidated. The initial rover position will be obtained through a triangulation usingobservations on orbital images and the very first set of surface images if common landmarks canbe found in these images. This location can then be improved and verified by UHF two-wayDoppler tracking and VLBI technology. As more ground images are acquired, landmarks seen inboth ground images and orbital images can be used to update landing site locations in the globalMars body-fixed reference system. Onboard rover localization techniques will perform roverlocalization tasks in real-time. The application of visual odometry will improve localization byovercoming problems associated with wheel odometry such as slippage and low accuracy.Finally, the bundle adjustment based rover localization method will build an image networkacquired by Pancam, Navcam and Hazcam cameras, as well as orbital images (such as Viking,MOC NA, and THEMIS images). The developed incremental and integrated bundle adjustmentmodels will supply improved rover locations and image orientation parameters, which are criticalfor generation of high quality landing site topographic mapping products. Based on the field testsperformed on Earth and Mars (MPF mission data), we expect that a 1 percent or better roverlocalization accuracy can be achieved during this mission. In addition, the bundle adjustmentresults will also enable us to produce high precision landing site topographic mapping productsincluding seamless panoramic image mosaics, DTM, and orthophotos.

3-D Shoreline Extraction from IKONOS Satellite Imagery

Shorelines are recognized as unique features on Earth. They have valuable properties for a diverse user community. At present, photogrammetry is the most popular technique used to capture a shoreline. With improved resolution and accuracy, commercial high-resolution satellite imagery is demonstrating a great potential in the photogrammetry application domain. One example is the utilization of IKONOS satellite imagery in shoreline extraction. IKONOS panchromatic imagery has a resolution of approximately one meter as well as the capabilities of stereo imaging. This article presents the results of an experiment in which we attempted to improve IKONOS Rational Functions (RF) for a better ground accuracy and to employ the improved RF for 3-D shoreline extraction using 1-meter panchromatic stereo images in a Lake Erie coastal area. Two approaches were investigated. One was to rectify the ground coordinates derived from vendor-provided RF coefficients using ground control points (GCPs). The other was to refine the RF coefficients using the GCPs. We compare the results from these two approaches. An assessment of the shoreline extracted from IKONOS images compared with the existing shoreline is also conducted to demonstrate the potential of the IKONOS imagery for shoreline mapping.

Digital Tide-Coordinated Shoreline

The shoreline is one of the most important features on earths surface. It is valuable to a diverse user community. But the dynamic nature of the shoreline makes it difficult to be represented in a naturally dynamic style and to be utilized in applications. The officially used shoreline, for example in nautical charts, is the so-called tide-coordinated shoreline. It is also the shoreline that makes the computation of shoreline changes and associated environmental changes meaningful. Mapping of the tide-coordinated shoreline has been very costly. On the other hand, instantaneous shorelines extracted from different data sources may be available. Also, high-resolution satellite and airborne imagery have the capacity of stereo imaging and can be used to extract instantaneous shorelines at a high accuracy and low cost. This article proposes an approach to derivation of digital tidecoordinated shorelines from (a) those instantaneous shorelines and (b) digital coastal surface models and a digital water surface model. Some preliminary study results, analysis, and the potential of the approach are discussed.

Rigorous Photogrammetric Processing of HiRISE Stereo Imagery for Mars Topographic Mapping

High-resolution (submeter) orbital imagers have opened up new possibilities for Mars topographic mapping with unprecedented precision. While the typical sensor model for Martian orbiters has been the linear-array charge-coupled device (CCD), the High-Resolution Imaging Science Experiment (HiRISE) instrument is based on a more complicated structure involving a combination of 14 separate linear-array CCDs. To take full advantage of this high-resolution capability without compromising imaging geometry, we have developed a rigorous photogrammetric model for HiRISE stereo image processing in which third-order polynomials are used to model the change in exterior-orientation parameters over time. A coarse-to-fine hierarchical matching approach was developed, and its performance was evaluated based on manually matched image points and manually measured features for a test area at the Mars Exploration Rover Spirit landing site. Using automatically selected tie points, we performed bundle adjustment (BA) to improve the accuracy of image pointing data and remove or reduce inconsistencies between the stereo pair and inconsistencies between overlapping CCDs in the same image mosaic. A method for the incorporation of jitter terms into the BA was developed and proved to be effective. We created a 1-m-resolution digital elevation model and an orthophoto using this methodology and compared them with topographic products from the U.S. Geological Survey.

Rock Modeling and Matching for Autonomous Long-Range Mars Rover Localization

This paper introduces the concept and design of a new integrated approach to long-range autonomous Mars rover localization based on the incremental bundle adjustment and visual odometry technologies that have been individually experimented with during the 2003 Mars Exploration Rover mission. The design result indicates that a rover would have a varying performance in traversing from 7.5 to 118 m within one traverse leg under various scenarios including camera systems and traverse geometry, while maintaining the onboard rover localization accuracy at 1%. To implement the proposed integrated approach, the key is to develop autonomous cross-site tie point selection algorithms for automatic generation of a sufficient number of high quality tie points to link all the images and to form the image network. New methods of rock extraction, rock modeling, and rock matching from multiple rover sites are developed to automate cross-site tie point selection. Rocks are extracted from three-dimensional ground points generated by stereo image matching, and then modeled using analytical surfaces such as hemispheroid, semiellipsoid, cone, and tetrahedron. Rocks extracted and modeled from two rover sites are matched by a combination of rock model matching and rock distribution pattern matching. The matched rocks are used as cross-site tie points for a subsequent bundle adjustment. The presented results show that the proposed cross-site tie point selection approach functions successfully for medium-range up to 26 m traverse legs.

Characterization of traverse slippage experienced by Spirit rover on Husband Hill at Gusev crater

Spirit rover experienced significant slips traversing Husband Hill. This paper analyzes the slippage Spirit experienced from Sol 154 to Sol 737. Slippage with respect to terrain type and slope is computed using data downlinked from the rover, rover position, and orientation estimations from visual odometry (VO) and photogrammetry based bundle adjustment (BA) method. Accumulated slippage reached a maximum of 83.86 m on Sol 648. However, as Spirit descended into the Inner Basin, the direction of slippage reversed, and accumulated slippage approached zero by the end of the entire traverse. Eight local regions with significant slips and nineteen traverse segments have been analyzed. Slippage was found to be highly correlated to slope direction and magnitude; the reverse of slope directions in the ascending and descending portions of the traverse proves to be the main contributor to the observed cancellation of slippage. While the horizontal component of the slippage almost canceled out, the difference in elevation continually accumulated, mainly during the ascent. In general, long traverse segments created more slips than short ones. This is reflected in both the accumulated and individual slippages. In considering the four major Mars terrain types, Spirit performed best on bedrock, managing to drive on slopes close to 30°. Fine-grain surfaces were the most challenging; though progress was made on slopes up to 15°, slippages of over 100% (more slippage than distance traveled) occurred for short segments. The results of this work can be incorporate into a traverse planning framework in which rover slippage is minimized. Results can be employed in landed planetary missions for precision navigation to avoid potentially dangerous regions by considering expected slippage.

Geometric Integration of Aerial and High-Resolution Satellite Imagery and Application in Shoreline Mapping

This paper investigates the geopositioning accuracy achievable from integrating IKONOS and QuickBird satellite stereo image pairs with aerial images acquired over a region at Tampa Bay, Florida. The results showed that the accuracy is related to a few factors of imaging geometry. For example, the geopositioning accuracy of a stereo pair of IKONOS or QuickBird images can be improved by integrating a set of aerial images, even just a single aerial image or a stereo pair of aerial images. Shorelines derived from the IKONOS and QuickBird stereo images, particularly the vertical positions, are compared with the corresponding observations of water-penetrating LiDAR and water gauge stations and proved that differences are within the limit of the geopositioning uncertainty of the satellite images.

Visual terrain mapping for Mars exploration

One goal for future Mars missions is to navigate a rover to science targets not visible to the rover, but seen in orbital or descent images. In order to support and improve long-range navigation capabilities, we generate 3D terrain maps using all available images, including surface images from the lander and/or rover, descent images from the lander, and orbital images from current and future Mars orbiters. The techniques used include wide-baseline stereo mapping for terrain distant from the rover, bundle adjustment for high-accuracy mapping of surface images, and structure-from-motion techniques for mapping using descent and orbital images. The terrain maps are compiled using a system for unifying multi-resolution models and integrating three-dimensional terrains.