PolyU scientists make great strides in lunar mapping

 　　HONG KONG, Sept. 9 (Xinhua) -- The Hong Kong Polytechnic 1 University (PolyU) announced Friday that its surveying experts had successfully developed methodologies for precise mapping of the Moon, after intensive analysis of the data captured by the Chinese lunar orbiter ChangE-1 and other lunar exploration missions.

　　According to the PolyU, the team has made significant contributions to lunar mapping. Their efforts culminated 2 in the development of a unique and innovative 3 approach to the creation of accurate 3D models of the lunar surface.
　　The team has produced the most updated parameters 4 of the lunar figure (the shape of the moon), which is essential for lunar mapping using 17.5 million laser altimetry measurements from the ChangE-1and the Japanese SELENE missions.
　　In addition, they also used the new topographic and gravity models to calculate improved crustal thickness and mass distribution of the Moon and established that the average thickness of the Moon's crust is about 40 km on the near side and 50 km on the far side.
　　It was introduced that the resulting lunar mapping was the hard work of a dedicated 5 research team led by Professor Chen Yong-qi, Emeritus 6 Professor of the Department of Land Surveying and Geo-Informatics, who is also serving on the Expert Committee of China's Lunar Exploration Programme (ECCLEP), with the concerted efforts of team members Prof. Chen Wu, Prof. Ding Xiao-li, Prof. Baki Iz, Dr. Bruce King, and Dr. Wu Bo.
　　According to Chen Yong-qi, the lunar mapping project started in 2006. The primary objective was to develop the methodologies and techniques for mapping the Moon surface, which is much more challenging than mapping the Earth's surface because of very few surveyed control points which are essential for accurate map making.
　　Statistics showed that there were only fourteen lunar laser ranging retro reflectors (LRRR) and Apollo lunar surface experiment package (ALSEP) transmitter sites with accurately 7 known coordinates 8 available only on the near side of the Moon, installed by the U.S. Apollo and former Soviet 9 Union Luna missions in the 1960s.
　　Moreover, according to the team, the gravitational field of the Moon is not as well-known as that of Earth, which means the accuracy of the computed 10 lunar satellite's position at any given time is lower than for Earth satellites, thus degrading the mapping accuracy and reliability 11.
　　In addition, the team expressed that highly reflective lunar surface created significant problems for the automatic processing of images to develop 3D models using the technique of photogramemtry, which is a widely used and highly reliable technique for the creation of maps and 3D models on Earth.
　　Furthermore, the team also revealed they had a plan to compare such data with other data sources in order to evaluate the performance of the ChangE mapping sensors 12. Since Chen Yong-qi is serving on the ECCLEP, the team has direct access to more recent data captured by the ChangE satellite.