Computer Laboratory

Technical reports

Signal maps for smartphone localisation

Chao Gao

February 2017, 127 pages

This technical report is based on a dissertation submitted August 2016 by the author for the degree of Doctor of Philosophy to the University of Cambridge, King’s College.


Indoor positioning has been an active research area for 20 years. Systems based on dedicated infrastructure such as ultrasound or ultra-wideband (UWB) radio can provide centimetre-accuracy. But they are generally prohibitively expensive to build, deploy and maintain. Today, signal fingerprinting-based indoor positioning techniques, which use existing wireless infrastructure, are arguably the most prevalent. The fingerprinting-based positioning system matches the current signal observations (fingerprints) at a device to position it on a pre-defined fingerprint map. The map is created via some form of survey. However, a major deterrent of these systems is the initial creation and subsequent maintenance of the signal maps. The commonly used map building method is the so-called manual survey, during which a surveyor visits each point on a regular grid and measures the signal fingerprints there. This traditional method is laborious and not considered scalable. An emerging alternative to manual survey is the path survey, in which a surveyor moves continuously through the environment and signal measurements are taken by the surveying device along the path. A path survey is intuitively better than a manual survey, at least in terms of speed. But, path surveys have not been well-studied yet.

This thesis assessed the path survey quantitatively and rigorously, demonstrated that path survey can approach the manual survey in terms of accuracy if certain guidelines are followed. Automated survey systems have been proposed and a commodity smart-phone is the only survey device required. The proposed systems achieve sub-metre accuracy in recovering the survey trajectory both with and without environmental information (floor plans), and have been found to outperform the state-of-the-art in terms of robustness and scalability.

This thesis concludes that path survey can be streamlined by the proposed systems to replace the laborious manual survey. The proposed systems can promote the deployment of indoor positioning system in large-scale and complicated environments, especially in dynamic environments where frequent re-survey is needed.

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BibTeX record

  author =	 {Gao, Chao},
  title = 	 {{Signal maps for smartphone localisation}},
  year = 	 2017,
  month = 	 feb,
  url = 	 {},
  institution =  {University of Cambridge, Computer Laboratory},
  number = 	 {UCAM-CL-TR-901}