Browsing by Author "Puussaar, Aare"

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Indoor Positioning Using WLAN Fingerprinting with Post-Processing Scheme
(Tartu Ülikool, 2014) Puussaar, Aare; Tartu Ülikool. Loodus- ja tehnoloogiateaduskond; Tartu Ülikool. Tehnoloogiainstituut
Information about a person’s position is a valuable piece of context information on which many application and location services are based upon. In outdoor environments the Global Positioning System (GPS) and Assisted GPS (A-GPS) are widely used and they perform reasonably well, but they underperform when there is no clear access to the sky, i.e. in indoor environments. Most of the research conducted and solutions developed aim for real-time indoor positioning or personal tracking, but to the author’s knowledge there are not many studies on the subject of post- processing. Post-processing has many benefits over real-time solutions, like preserving battery life of a mobile device, leveraging bigger processing power, using more complex algorithms that cannot run on mobile devices, and ultimately getting better accuracy on a person’s movements tracks. In this thesis, an Indoor Positioning System (IPS) using WLAN fingerprinting with post- processing scheme is proposed. The system uses a large set of fingerprinted Received Signal Strength (RSS) collections obtained in the offline phase and references them in post-processing against data collected in the online phase. A series of field experiments have been conducted in University of Tartu’s Faculty of Mathematics and Computer Science building. The results show that with a post-processing scheme more computationally extensive algorithms can be used and better accuracy achieved than in real-time.
Requirements and analysis of Multispectral Volume Scattering Meter
(Tartu Ülikool, 2011) Puussaar, Aare
The volume scattering function (VSF), which describes the angular distribution of light scattered from an incident beam, is a fundamental inherent optical property of the aquatic environment. Despite its fundamental nature, there is little known about the range of variability in the VSF in the aquatic environment. This is mainly because the measurements of the function are difficult to perform. A lot of currently used radiate transfer models are based on a very limited set of measurements, which are made over 20 years ago. For the correct calculations of the radiate transfer, it is essential to know the variations of the phase function. Instruments, which have previously been used for measuring VSF, were complicated, bulky and most importantly: they are not able to take measurements of the function in full angular range. The purpose of this document is to describe the system requirements specifications of a Multispectral Volume Scattering Meter (MVSM). Document describes a new instrument for measuring the volume scattering function of seawater and other natural waters across a hemispheric angle range. System requirements and analysis is put together following modern methodology and standards. The measurement principles implemented in the device, are based on static scatter approach. Photomultiplier tube (PMT) is used to detect scattering light at different angles. Device’s mechanistic approach involves a use of a special periscope prism and a novel light shadow method.