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|Title:||Integration of multi-source lunar orbiter camera imagery and laser altimeter data for precision lunar topographic modeling|
|Keywords:||Moon -- Surface.|
Image processing -- Digital techniques.
Hong Kong Polytechnic University -- Dissertations
|Publisher:||The Hong Kong Polytechnic University|
|Abstract:||Lunar topography is one of the principal measurements quantitatively describing the body of the Moon. Lunar topographic information is critical for understanding the ring structure, mare fill, ejecta, and other crustal features of impact basins. They have major implications for determining the origin and evolution of the Moon. High resolution and precision lunar topographic data also play critical roles in lunar exploration missions, in such areas as the selection of landing sites, the safe maneuvering of lunar vehicles or robots, and the navigation of astronauts in ground operations. Lunar orbiter imagery and laser altimeter data are two major data sources for lunar topographic modeling. Lunar exploration missions so far has returned vast amounts of lunar orbiter imagery and laser altimeter data with different resolutions and levels of uncertainty. Most previous related research has processed the orbiter imagery and laser altimeter data for lunar topographic modeling separately. However, there are usually inconsistencies among the lunar topographic models derived from the multisource lunar topographic datasets. Research in the past has rarely emphasized multi-source (cross-mission and cross-sensor) data integration for precision lunar topographic modeling. This research aims to integrate multi-source lunar orbiter imagery and laser altimeter data for precision lunar topographic modeling by developing innovative integration approaches and strategies. Firstly, the research presents a comparative study of multi-source lunar topographic datasets and the topographic models derived from them. A novel surface matching method based on multi-features which incorporated feature points, feature lines and surface patches was developed for comparison and co-registration of lunar DTMs derived from multi-source datasets. The laser altimeter data from Chang’E-1, SELENE, and LRO in the Apollo 15 landing area and the Sinus Iridum area were examined and different levels of inconsistencies among these topographic datasets were found. In the Apollo 15 landing area, the LRO laser altimeter data are about 218 m higher than the Chang’E-1 laser altimeter data, and there are about 25 m offset between the two datasets in the horizontal direction. For the SELENE and LRO laser altimeter datasets, the SELENE data are generally about 164 m higher than the LRO data, and there are about 40 m offset between them in the horizontal direction. In the Sinus Iridum area, the SELENE laser altimeter data are about 230 m higher than the Chang'E-1 data, and there are about 470 m offset between them in the horizontal direction. There are about 56 m offset between the SELENE and LRO laser altimeter datasets in the horizontal direction, and their elevations are fairly consistent in the study area. The developed multi-feature-based surface matching method was proven to be able to effectively compare and co-register multiple lunar DTMs. Secondly, the research studied the integration of single-strip imagery and laser altimeter data both from the Chang’E-1 datasets for precision lunar topography modeling. Inconsistencies were found between the Level 2C Chang'E-1 imagery and laser altimeter data, as indicated by the mis-registrations from 3 pixels to 18 pixels in image space in the landing areas of Apollo 15 and 16. A bundle adjustment approach was developed for the integration of Chang’E-1 imagery and laser altimeter data, in which the participants are the laser altimeter points, image exterior orientation (EO) parameters, and tie points collected from the stereo images. A weighting scheme was designed for the participants in the adjustment and a local surface constraint was imposed to improve the adjustment performance. The output of the bundle adjustment was the refined image EO parameters and laser ground points. The proposed bundle adjustment approach was evaluated based on the experimental results using the Chang'E-1 datasets in the landing areas of Apollo 15 and 16. The developed bundle adjustment approach was proven to be able to effectively reduce the mis-registrations in image space to about one pixel level. From the resulting improved image EO parameters and laser ground points, consistent and precision lunar topographic models can be generated.|
Thirdly, the research further studied cross-mission and cross-sensor data integration for precision lunar topographic by using multi-strip Chang'E-2 imagery and LRO laser altimeter data. The integration of cross-mission and cross-sensor data is a more challenging task, because the influences from the uncertainties between the datasets collected by different sensors from different missions is more significant than using a single set of data from the same mission. This research developed a combined block adjustment method for the integration of Chang'E-2 imagery and LRO laser altimeter data. The participants of the combined block adjustment include the orientation parameters of the Chang'E-2 images, the intra-strip tie points derived from the Chang'E-2 stereo images of the same orbit, the inter-strip tie points derived from the overlapping area of two neighbor Chang'E-2 image strips, and the LRO laser altimeter points. Two constraints are incorporated into the combined block adjustment including a local surface constraint and an orbit height constraint, and they are specifically designed to remedy the large inconsistencies between the Chang'E-2 and LRO datasets. The output of the combined block adjustment is the improved orientation parameters of the Chang'E-2 images and ground coordinates of the LRO laser altimeter points, from which precision lunar topographic models can be generated. The performance of the combined block adjustment approach was evaluated using the Chang'E-2 imagery and LRO laser altimeter data in the Apollo 15 landing area and the Sinus Iridum area. The results show that the mean absolute image residuals were drastically reduced from tens of pixels before the block adjustment to sub-pixel level after the block adjustment. DTMs with 20 m resolution were generated based on the improved EO parameters of the Chang'E-2 imagery after the combined block adjustment. Comparison of the Chang'E-2 DTM with the LRO DTM showed a good level of consistency. Based on the investigations reported in this dissertation, various algorithms were implemented and a software named LunarTool was developed using Microsoft Visual C++ 2010. Various detailed topographic modeling results such as DTMs and orthophotos were generated. The topographic products in the Sinus Iridum area directly contribute to the assessment and selection of potential landing sites for the Chang'E-3 lunar landing mission. The cross-mission and cross-sensor data integration strategy presented in this research is very valuable for lunar topographic modeling, which will ensure the study of offsets, trends, and error analysis in various lunar topographic datasets, will facilitate the proper calibration and registration of the datasets, and in turn will permit the full comparative and synergistic use of the datasets. The cross-mission and cross-sensor data integration strategy can also be used in other similar applications on Earth, Mars, and possibly other planets in the outer space.
|Description:||xiii, 154 leaves : col. ill. ; 30 cm.|
PolyU Library Call No.: [THS] LG51 .H577P LSGI 2014 Guo
|Rights:||All rights reserved.|
|Appears in Collections:||Thesis|
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Checked on Jul 9, 2017
Checked on Jul 9, 2017
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