Description: PolyU logo.pngDescription: Faculty.pngDescription: LSGI logo.png



What’s New




Awards & Honors

Community Services

Resources & Links


Contact Us


Welcome to the homepage of Micro-Laboratory of Atmospheric Research and Geomatics Engineering (Micro-LARGE)


Recently updated (This page was last updated on September 02, 2016)


[Sept. 2, 2016] We are pleased to see that two co-authored papers have been accepted by the Journal of Geophysical Research - Space Physics, on the same day September 01, 2016. One paper’s lead author is Dr. Tao YU, a professor at the China University of Geoscience (Wuhan) and a Research Associate at PolyU. Another paper’s lead author is Dr. Sanjay Kumar, a Research Associate of PolyU. Congratulations to Dr. YU and Dr. Kumar! Click the Research for more details.


[Sept. 2, 2016] We are pleased to announce that Jenny Yang’s paper has been accepted the GPS Solutions, on 28 August 2016. Congratulations to Jenny! Click the Research for more details.



[Aug. 29, 2016] Dr. Liu’s Research Proposal was successfully funded by the General Research Fund (GRF) Scheme of Research Grants Council (RGC), the Hong Kong SAR Government. The RGC’s fund application is very competitive every year and only the real top quality proposals are selected to be funded. The funding size to Dr. Liu’s project is HK$844,559, which represents the largest project in terms of funding size in the Faculty of Construction and Environment, PolyU in 2016. PhD students are to be recruited and applications are welcome!


[Aug. 29, 2016] Eventually our website has been updated by myself. In the past one to two years, a number of students promised to update/redesign my website but it was never realized.


[Dec. 03, 2014] We are pleased to share with you that the following papers have been accepted for publication at top journals.


Xu, Rui, Zhizhao Liu, and Wu Chen. 2014. “Improved FLL-Assisted PLL with in-Phase Pre-Filtering to Mitigate Amplitude Scintillation Effects.” GPS Solutions, June, 1–14. doi:10.1007/s10291-014-0385-5.


Wong, Man Sing, Xiaomeng Jin, Zhizhao Liu, Janet Nichol, and P. W. Chan. 2014. “Multi-Sensors Study of Precipitable Water Vapour over Mainland China.” International Journal of Climatology, November, n/a – n/a. doi:10.1002/joc.4199.


Weng, Duojie, Shengyue Ji, Wu Chen, and Zhizhao Liu. 2014. “Assessment and Mitigation of Ionospheric Disturbance Effects on GPS Accuracy and Integrity.” The Journal of Navigation 67 (03): 371–84. doi:10.1017/S0373463314000046.


Luo, Weihua, Zhizhao Liu, and Min Li. 2014. “A Preliminary Evaluation of the Performance of Multiple Ionospheric Models in Low- and Mid-Latitude Regions of China in 2010–2011.” GPS Solutions 18 (2): 297–308. doi:10.1007/s10291-013-0330-z.


Liu, Zhizhao, Biyan Chen, Sai T. Chan, Yunchang Cao, Yang Gao, Kefei Zhang, and Janet Nichol. 2014. “Analysis and Modelling of Water Vapour and Temperature Changes in Hong Kong Using a 40-Year Radiosonde Record: 1973-2012.” International Journal of Climatology, April, n/a – n/a. doi:10.1002/joc.4001.


Li, Zhongbin, Zhizhao Liu, and Wenzhong Shi. 2014. “Semiautomatic Airport Runway Extraction Using a Line-Finder-Aided Level Set Evolution.” IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing Early Access Online. doi:10.1109/JSTARS.2014.2298332.


[March 21, 2014] We are pleased to share with you that the following papers have been accepted for publication at top journals.


Biyan Chen and Zhizhao Liu (*) (2014), Voxel-Optimized Regional Water Vapor Tomography and Comparison with Radiosonde and Numerical Weather Model, Journal of Geodesy, accepted (IF: 2.808)


Zhizhao Liu (*), Biyan Chen, Sai Tick Chan, Yunchang Cao, Yang Gao, Kefei Zhang, and Janet Nichol (2014), Analysis and modeling of water vapor and temperature changes in Hong Kong using a 40-year radiosonde record: 1973-2012. International Journal of Climatology, accepted (IF: 2.479)


Cai, Changsheng, Xiaomin Luo, Zhizhao Liu (*) and Qinqin Xiao (2014), Galileo Signal and Positioning Performance Analysis Based on Four IOV Satellites. Journal of Navigation, accepted (IF: 0.618, Relative ranking within Categories: Engineering, marine 5/14)


Zhongbin Li, Zhizhao Liu, and Wenzhong Shi (*) (2014), Semiautomatic Airport Runway Extraction Using a Line-Finder-Aided Level Set Evolution, IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing (IEEE JSTARS), Accepted (2013 IF: 2.874)



[November 29, 2013] I am very pleased to Dr. Liu’s application for the Croucher Summer Course “GPS/Beidou/GNSS Satellite Positioning and Navigation and Earth Observation” has been successfully granted by The Croucher Foundation Limited, Hong Kong, 5 years, 2014-2018. The generous support from The Croucher Foundation Limited is HK$1,708,500, which will be paid in three equal installments of HK$569,500. Thank you The Croucher Foundation Limited!



[November 29, 2013] I am very pleased to announce that TWO (2) Public Policy Research (PPR) projects are funded. Dr. Liu is a Co-Investigator in these two projects.  Thank you Central Policy Unit, Government of Hong Kong Special Administrative Region!


The project information is:

2013, Co-Principal Investigator (Co-PI), “A Remote Sensing Study of Solar Energy Supply in Cloud-prone Areas of Hong Kong”, Public Policy Research Funding Scheme (2013-2014), Central Policy Unit, Government of Hong Kong Special Administrative Region (HKSAR), 12 months, HK$359,869.50. [PI: Dr. Charles Man Sing Wong, Assistant Professor, Department of Land Surveying & Geo-Informatics, The Hong Kong Polytechnic University] 


2013, Co-Principal Investigator (Co-PI), “Study on the development potential and energy incentives of rooftop solar photovoltaic applications in Hong Kong”, Public Policy Research Funding Scheme (2013-2014), Central Policy Unit, Government of Hong Kong Special Administrative Region (HKSAR), 12 months, HK$424,120. [PI: Dr. Vivien Lu, Associate Professor, Department of Building Services Engineering, The Hong Kong Polytechnic University]


[November 20, 2013] Dr. George Liu was honored as a Guest Professor of the GNSS Research Center, Wuhan University.


[October 25, 2013] Dr. George Liu’s proposal was funded by the University.


[October 08, 2013] Dr. George Liu joined the HKIES society.





[September 22, 2013] We are very pleased to announce that Dr. George Zhizhao Liu received the “Best Researcher of the Year 2013” from the Department of LSGI. This news was announced on 19 September 2013 by the Departmental Research Committee.


[August 18, 2013] We are very pleased to announce that Dr. George Zhizhao Liu received the 2013 Dean’s Award. Dr. Liu joined other 9 colleagues in the Faculty of Construction and Environment (FCE) to receive this prestigious award. Also he is the only recipient from the Department of LSGI. As the recipient of the Dean’s Award,

Dr. Liu will be honoured at the Faculty Congregation and Prize Presentation Ceremony to be held November 2013 with a cash prize of HK$15,000. In addition, he will be awarded a research grant of HK$200,000 to support his future research!


More details can be found at the Faculty’s eBulletin:


[July 08, 2013] We are very delighted to announce the annual Hong Kong Research Grants Council (RGC)’s General Research Fund (GRF) project application submitted by Dr. Liu last year is successfully funded!


This news was officially announced 28 June 2013. Dr. Liu’s project titled “Investigating the Ionospheric Scintillation Characteristics using Space- and Ground- Based GNSS Observations in Hong Kong during Solar Maximum” is successfully selected to fund by the RGC for 36 months. This is one of PolyU’s 138 GRF projects funded by RGC this year. Dr. Liu was successfully funded in the past 3 years in a row. One PhD student and one Research Associate (or Research Assistant) will be recruited to work on this project. Applicants must send email to contact Liu immediately.



[June 07, 2013] We are very delighted that the MicroLARGE Lab has established the Hong Kong’s FIRST GNSS and Radiosonde collocation station at Hong Kong Observatory’s facility at King’s Park, Kowloon, Hong Kong. This is the first time that the GNSS station is established just nearby the Hong Kong’s only Radiosonde station. Both GNSS receiver and Radiosonde are used to observe atmospheric water vapor. The collocation of two observation techniques allows a direct comparison of the water vapor measurements of these two methods. The Radiosonde technique is traditionally believed a standard reference to which other water vapor observation technique should be compared. The establishment of such a facility will allow our researchers to gain more data to study the atmospheric water vapor changes in Hong Kong and to have more insightful understanding of the observation accuracy of each method.

[L to R: Dr. Weiwei Song (PolyU), Mr. Engineer (HKO), Dr. David Lam (HKO), Mr. Wang-chun Woo (HKO), Dr. George Liu (PolyU)]


[L to R: Mr. Biyan Chen (PolyU), Dr. Weiwei Song (PolyU), Mr. Engineer (HKO), Dr. David Lam (HKO), Mr. Wang-chun Woo (HKO)]



[May 26, 2013] Recently, Dr. Liu made a presentation of a paper titled “A Comparison of GNSS-based Ionospheric Scintillation Observations in North and South Hong Kong” at the recent 2013 Pacific PNT held at Honolulu, Hawaii, USA during April 22-25, 2013. This paper was coauthored by Zhizhao Liu, Rui Xu, Yu Morton, Jisheng Xu, Wouter Pelgrum, Steve Taylor, Wu Chen and Xiaoli Ding.



[May. 22, 2013] We are very pleased to announce that Dr. Liu is to receive the Excellent Paper Award from the 2013 4th Chinese Satellite Navigation Conference (CSNC 2013) in Wuhan, China.


In the recent 2013 China Satellite Navigation Conference (CSNC) held May 15-17 in Wuhan, Dr. George Zhizhao Liu from the Department of Land Surveying & Geo-Informatics (LSGI) received the Excellent Paper Award for his paper “The First PPP-based GPS Water Vapor Real-Time Monitoring System in Pearl-River-Delta Region, China” co-authored with Research Associate Dr. Min Li. This paper presents their research findings of developing the first atmospheric water vapor real-time monitoring system for the Pearl-River-Delta (PRD) region using the latest Global Positioning System (GPS) Precise Point Positioning (PPP) technique. Based on their technique, now the amount of water vapor in the atmosphere over the PRD region can be quickly and accurately computed from GPS satellite signals. Since April 2012, the PolyU researchers have been supplying their atmospheric water vapor data to the meteorological agencies around the PRD region to support their daily services and research, including Hong Kong Observatory, Macao Meteorological and Geophysical Bureau, Guangdong Meteorological Bureau and Shenzhen Meteorological Bureau.


This year is the first time for CSNC to have the Excellent Paper Award. Dr. Liu was one of the nine award recipients out of 629 paper submissions. This research work was supported by the General Research Fund (GRF) of Hong Kong Research Grants Council (RGC).


[May 11, 2013] We are very pleased to announce that Dr. George Zhizhao Liu was given an honor of Individual Award of Shenzhen Virtual University Park

for National Research Project, by the Shenzhen Municipal Science and Technology Innovation Council December 2012.



[Jan. 04, 2013] Dr. Liu and his research team visited the Hong Kong Observatory, Hong Kong Special Administrative Region (HKSAR). Dr. Liu was also invited to give an open presentation titled “GNSS for Precise Water Vapor and Ionosphere Space Weather Monitoring” for the HKO colleagues. Dr. Liu and his team were guided by Mr. S. T. Chan, Senior Scientific Officer of HKO, to visit the weather forecasting center.


[Dec. 12, 2012] The Inaugural Early Career Award Recipient (首届杰出青年学者奖”), Hong Kong Research Grants Council (RGC), Hong Kong Special Administrative Region (HKSAR). Dr. Liu was one of the 19 recipients out of 334 applicants across all the universities in Hong Kong in 2012 (success rate: 5.69%). He is also one of only 3 recipients in PolyU and one of 6 recipients in the Engineering Panel under Hong Kong RGC.


Dr. Liu received the Early Career Award from the Chairman of the Engineering Panel of Hong Kong Research Grants Council (Dec. 12, 2012)



The six recipients of Early Career Award of the Engineering Panel and the Engineering Panel Chairman of Hong Kong Research Grants Council (Dec. 12, 2012)




[July 23, 2012] We are pleased to share with you that our research project “Innovative Real-Time Cycle Slip Detection and Rectification for High Precision GPS Positioning” led by Dr. George Zhizhao Liu is funded by the Early Career Scheme (ECS), Hong Kong Research Grants Council (RGC), Hong Kong SAR Government. This project, together with 19 other projects across all the universities in Hong Kong, will be recognized with an

“Early Career Award” (ECA), which is the first time to give ECA in the history of Hong Kong RGC.

For this project, one PhD student will be funded for three (3) years. Interested applications are welcome to contact Dr. Liu.


[July 23, 2012] We are pleased to share with you that our paper “Cycle slip detection and repair for undifferenced GPS observations under high ionospheric activity” co-authored by Changsheng Cai • Zhizhao Liu • Pengfei Xia • Wujiao Dai is published online @ GPS Solutions 4 July 2012. As of 23 July 2012 (20 days after the online publication), this paper has been downloaded 174 times, ranked 2nd in the list of most downloaded papers in the 30-days category. This paper can be downloaded @



[May 29, 2012]  The Hong Kong GPS-based Real-time Water Vapor Monitoring System (GRWVMS) has been successfully operating more than 40 days (since its first day 19 April 2012). This is one of the countable GRWVMS in the world. To our knowledge, similar systems are only available at a limited number of organizations, such as:


2. USA: UCAR Suominet network:

3. Netherlands: KNMI (Royal Netherlands Meteorological Institute)


[February 10, 2011] As of 10 Feb. 2011 our paper (link here) is ranked one of the 5 most downloaded papers in Journal of Geodesy based on the downloads in the past 77 days since its first day of online publication, one of the internationally well recognized journals in Geomatics.

This paper developed a fully automated cycle slip detection and repair algorithm for dual-frequency GPS carrier phase measurements. It can be safely said that the cycle slip problem that have been hanging over the GPS community as long as the GPS history itself (~30 years) is well resolved.


This algorithm is extremely effective for high rate GPS data like 1Hz or higher. Virtually any size of cycle slips can be detected and repaired.


For low rate GPS data (like 30 sec data interval or larger) this algorithm can work for many cycle slip cases but it might be a little difficulty for small cycle slips.


This method has been extensively tested and examined in many scenarios such as:

o  High dynamics (space-borne GPS receiver payload on COSMIC satellite)

o  Highly disturbed ionosphere (daily Kp index =7.6 on 31 March 2001, the 4th highest daily Kp value in the past 30 years)


We look forward to hearing your feedback and your comments/suggestions are always welcome.


Geomatics, an incredibly critical technology in this information era!


[April 21, 2010] I am very pleased that my students have produced a beautiful Google Earth KML map based on their final year project. In their final year project, the 3-girl group used the GPS RTK to survey one of the most popular cycling paths in Hong Kong (from Tai Po to Sha Tin). It is quite safe to say this Google Earth map for this HK cycling path is the most comprehensive, the most accurate (only a few centimeters of error) information that is accessible for free by the general public.


You can download this Google Earth KML map to your computer from here (right click mouse and save link as …). If you don’t have the Google Earth yet, you can download it for free from


[Jan.10, 2010](This is an excerpt of my speech given May 05, 2007 at my Toastmaster club). In this world, scientists, engineers, researchers, and actually many people are working hard every day to try to answer the following 6 most fundamental questions more correctly and more precisely:

1) When  2) Where  3) Who  4)What  5)Why  6)How

At present, we can easily answer “When” in a completely numerical way because our time has been digitalized, for instance: the UTC time at this point of writing is: 2010-01-19 15:22:20. The numerical expression of time is an important progress in human being history and it is essential in this information era. So how about the other 4W1H questions? Can you also use numbers to answer the remaining 4W1H questions? Answer is yes or no. If you use Geomatics technology, you can answer the Where  numerically too. Without geomatics, you can’t. Why? The answer is simple. For example, Hong Kong’s latitude and longitude is: 22°20 North,        114°11 East. So you can see the location of Hong Kong can be easily described in numeric numbers. How to get these numbers? It is a part of geomatics technology – using Global Positioning System (GPS). With GPS, you may locate anywhere in the world numerically and display it on your computer screen. This is the power and beauty of geomatics technology – answering one of the world’s most fundamental questions “WHERE” in a numerical way, a way people have never thought of and a way that is so critical in today’s information era.


With GPS technology, now any objects in our 4-dimensional space-time domain can be completely digitalized and numerically stamped. This is the contribution our geomaticians are making to the society.


[Dec03, 2009] Immediate Research Associate Post Open: (!new!)

There is currently one Research Associate Post open. The interested ones can find more

1.    information here (English Version) or (Chinese Version). Thank you!



[Dec03, 2009] On December 3rd, 2009, this website is drastically modified and improved to the current version. If you have an interest to join this group or have any comments, please don’t hesitate to contact us.


[Dec01, 2009] On December 1st, 2009, I am very pleased to welcome Rui Xu to the Micro-LARGE. She is the first student and first PhD student joining this Lab. She is from Nanjing University of Aeronautics and Astronautics (NUAA) and will complete her PhD studies under the joint

supervision of Prof. Wu Chen and myself. Welcome Rui!