Dr.ir. A.A. (Sandra) Verhagen

Profile

Sandra Verhagen obtained her MSc and PhD in geodesy and is now an assistant professor at the department of Geoscience and Remote Sensing of Delft University of Technology. In 2007 she received a VENI grant from the Dutch Science Foundation. From 2007 to 2011 she was the president of Commission 4 “Positioning and Applications” of the International Association of Geodesy. In 2012 she was a visiting research fellow at the GNSS Research Centre of Curtin University, Perth in Australia. Currently, she is theme leader "Sensing from Space" of the Delft Space Institute.

Research themes

• Global Navigation Satellite Systems
• Precise positioning
• Integer ambiguity resolution (LAMBDA)
• Quality control
• Formation flying and attitude determination
• Hydrographic surveying

Research

Research interests of Sandra Verhagen are in the domain of mathematical geodesy with a focus on carrier phase ambiguity resolution, error modelling & correction and quality control for real-time kinematic GNSS applications, including attitude determination and formation flying of aircraft ans spacecraft. Furthermore, she is working on the development of a risk-based survey policy for hydrographic surveying.

Educational activities

Courses:

• CIE4611 Geo-measurement processing
• CIE4614 Land surveying and civil infrastructures
• CIE4615 Geoscience and Remote Sensing fieldwork (also see our weblog)
• CIE4522 GPS for Civil Engineering and Geoscience
• MOOC OT.1X Observation Theory: estimating the unknown
• Previously taught: Satellite Navigation, Probability and Statistics, Data Quality Control

Sandra is the graduation and internship coordinator of the Master track Geoscience and Remote Sensing.

Projects

• GARADA, SAR formation flying, funded by Australian Space Research Program
• New carrier phase processing strategies for next generation GNSS positioning, funded by CRCSI Australia
• Compass, Galileo and GPS for improved ionosphere modeling, Joint research project with Institute of Geodesy and Geophysics, Wuhan, funded by KNAW and Chinese Academy of Science
• SMARTSEA - Safe navigation by optimizing sea bed monitoring and waterway maintenance using fundamental knowledge of the sea bed dynamics, funded by STW
• TREASURE - Training, Research and Applications network to Support the Ultimate Real time high accuracy EGNSS solution, a  MARIE SKŁODOWSKA-CURIE ACTIONS Innovative Training Network (ITN) funded by the EU

Key publications

• Verhagen, S. (2016), "GNSS Ambiguity Resolution and Validation". In: Grafarend, E. (ed.) Encyclopedia of Geodesy, Springer International Publishing, 1-4 [DOI]
• Li, B.; Zhang, L. & Verhagen, S. (2016). "Impacts of BeiDou stochastic model on reliability: overall test, w-test and minimal detectable bias". GPS Solutions, 1-18 [DOI]
• Hou Y, Verhagen S and Wu J (2016), "A data driven partial ambiguity resolution: Two step success rate criterion, and its simulation demonstration", Advances in Space Research. Vol. 58(11), pp. 2435 - 2452. [DOI]
• Hou Y, Verhagen S and Wu J (2016), "An Efficient Implementation of Fixed Failure-Rate Ratio Test for GNSS Ambiguity Resolution", Sensors. Vol. 16(7), pp. 945. [DOI]
• Wang, L. & Verhagen, S. (2015), "A new ambiguity acceptance test threshold determination method with controllable failure rate", Journal of Geodesy, Vol. 89(4), pp. 361-375. Springer Berlin Heidelberg. [DOI]

• Verhagen, S. & Teunissen, P. (2014), "Ambiguity resolution performance with GPS and BeiDou for LEO formation flying", Advances in Space Research, 54, 830-839  [DOI]
• Ober, B., Imparato, D., Verhagen, S., Tiberius, C., Veerman, H., Van Kleef, A., Wokke, F., Bos, A. & Mieremet, A. (2014), "Empirical integrity verification of GNSS and SBAS based on the extreme value theory", Navigation, 61, 23-38. [DOI] 
• Li, B., Verhagen, S. & Teunissen, P.J.G. (2013), " Robustness of GNSS integer ambiguity resolution in the presence of atmospheric biases", GPS Solutions, Vol. 18, pp. 283-296. [DOI]
• Verhagen, S., Li, B. & Teunissen, P.J.G. (2013), "Ps-LAMBDA: Ambiguity Success Rate Evaluation Software for Interferometric Applications", Computers & Geosciences, Vol. 54, pp. 361-376. [DOI]
• Verhagen, S. & Teunissen, P.J.G. (2012), "The ratio test for future GNSS ambiguity resolution", GPS Solutions, Vol. 17(4), pp.535-548. [DOI]
• Giorgi, G., Teunissen, P.J.G., Verhagen, S. & Buist, P.J. (2012), "Instantaneous Ambiguity Resolution in Global-Navigation-Satellite-System-Based Attitude Determination Applications: A Multivariate Constrained Approach", AIAA Journal of Guidance, Control, and Dynamics, Vol. 35(1), pp. 51-67. [DOI]
• Verhagen, S. (2005), "On the reliability of integer ambiguity resolution", Navigation, Vol. 52(2), pp. 99-110.
• Verhagen, S. (2005), "The GNSS integer ambiguities: estimation and validation" PhD dissertation, Delft University of Technology, Publications on Geodesy, Vol. 58, Netherlands Geodetic Commission, Delft. [URL]
• Verhagen, S. (2004), "Integer ambiguity validation: an open problem?", GPS Solutions, Vol. 8(1), pp. 36-43. [DOI]
• Verhagen, S. (2002), "Studying the performance of Global Navigation Satellite Systems: A new software tool", GPS World, Vol. 13(6), pp. 60-65.   

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