scholarly journals Assessment of Smartphone Positioning Data Quality in the Scope of Citizen Science Contributions

2017 ◽  
Vol 2017 ◽  
pp. 1-11 ◽  
Author(s):  
Angel J. Lopez ◽  
Ivana Semanjski ◽  
Sidharta Gautama ◽  
Daniel Ochoa
Keyword(s):  
Data Quality ◽  
Survey Methods ◽  
Travel Behaviour ◽  
Global Navigation Satellite Systems ◽  
Mobility Patterns ◽  
Satellite Systems ◽  
Mobility Behaviour ◽  
Global Navigation Satellite ◽  
Behaviour Data

Human travel behaviour has been addressed in many transport studies, where travel survey methods have been widely used to collect self-reported insights of daily mobility patterns. However, since the introduction of Global Navigation Satellite Systems (GNSS) and more recently smartphones with built-in GNSS, researchers have adopted these ubiquitous devices as tools for collecting mobility behaviour data. Although most studies recognize the applicability of this technology, it still has limitations. These are rarely addressed in a quantified manner. Often the quality of the collected data tends to be overestimated and these errors propagate into the aggregated results providing incomplete knowledge of the levels of confidence of the results and conclusions. In this study, we focus on the completeness aspects of data quality using GNSS data from four campaigns in the Flanders region of Belgium. The empirical results are based on mobility behaviour data collected through smartphones and include more than 450 participants over a period of twenty-nine months. Our findings show which transport mode is affected the most and how land use affects the quality of the collected data. In addition, we provide insights into the time to first fix that can be used for a better estimation of travel patterns.

scholarly journals EVALUATION AND TAILORING OF GLOBAL GEOPOTENTIAL MODELS IN THE DETERMINATION OF GRAVITY FIELD IN SERBIA

2020 ◽  
Vol 14 (1) ◽  
Author(s):  
Oleg Odalović ◽  
Danilo Joksimović ◽  
Dušan Petković ◽  
Marko Stanković ◽  
Sanja Grekulović
Keyword(s):  
Global Navigation Satellite Systems ◽  
Satellite Systems ◽  
Average Value ◽  
Free Air ◽  
Geopotential Models ◽  
Normal Heights ◽  
Discrete Values ◽  
Global Navigation Satellite

Within this paper, we evaluated the quality of three Global Geopotential Models entitled: EGM96,EGM2008, and GOCO05c. The models were evaluated by using 1001 terrestrial discrete values ofheight anomalies determined by Global Navigation Satellite Systems and normal heights, which weconsidered to be true values within this research. In addition to the quality evaluation, we tailoredthe models by using more than 80000 free air anomalies. The results obtained from the evaluationand tailoring indicate that by using the GOCO05c it is possible to determine a set of anomaly heightsacross Serbia, which are in agreement with terrestrial values with an average value of -7 cm, thestandard deviation of ±9 cm and with the range of 44 cm.

scholarly journals Evaluation of normal heights by the means of global navigation satellite systems and global geopotential model

2015 ◽  
Vol 95 (4) ◽  
pp. 103-124 ◽  
Author(s):  
Oleg Odalovic ◽  
Danilo Joksimovic ◽  
Sanja Grekulovic ◽  
Miljana Todorovic-Drakul ◽  
Jovan Popovic
Keyword(s):  
Global Navigation Satellite Systems ◽  
Geopotential Model ◽  
Navigation Satellite ◽  
Normal Height ◽  
Satellite Systems ◽  
Normal Heights ◽  
Global Navigation ◽  
Global Navigation Satellite ◽  
Ellipsoid Heights

This paper presents geometrically and physically defined height systems, along with their evaluation by the means of Global Navigation Satellite Systems (GNSS) and Global Geopotential Models (GGM). The paper defines ellipsoid heights as an instance of geometrically defined heights; with physically defined heights being represented by definitions of orthometric and normal heights. Methods of normal heights calculation by the means of ellipsoid heights are presented in detail, as determined using the GNSS and height anomalies calculated from the GGM application. Apart from the above, numerical part of the paper evaluates normal height values and compares them to their conditionally accurate values at 1073 points with relatively uniform distribution over the entire territory of Serbia. Conditionally accurate values had been determined by the means of classical geodetic terrestrial methods. Under the procedure of evaluating normal height values, GGM - GGM05C was used, as created in 2016 by the Center for Space Research, University of Texas at Austin. In order to evaluate the quality of applying the model above, data on normal heights evaluation were also presented, using the GGM EGM96, created in 1996 by the National Imagery and Mapping Agency (NIMA), Goddard Space Flight Center (GSFC - NASA) and Ohio State University, presently being the most commonly used model. The comparison above indicates that application of the GGM05C model provides 50 % greater quality of normal heights evaluations against the ones obtained using the EGM96 model.

scholarly journals QUALITY OF SATELLITE COMMUNICATION IN SELECTED MOBILE ANDROID SMARTPHONES

2021 ◽  
Vol 11 (4) ◽  
pp. 32-37
Author(s):  
Przemysław Falkowski-Gilski
Keyword(s):  
Mobile Devices ◽  
Satellite Communication ◽  
Urban Environments ◽  
Global Navigation Satellite Systems ◽  
Mobile Terminals ◽  
Everyday Activity ◽  
Satellite Systems ◽  
Global Navigation Satellite ◽  
Application Developers

Today, thanks to mobile devices, satellite communication is available to anyone and everywhere. Gaining information on one’s position using GNSS (Global Navigation Satellite Systems), particularly in unknown urban environments, had become an everyday activity. With the widespread of mobile devices, particularly smartphones, each person can obtain information considering his or her location anytime and everywhere. This paper is focused on a study, considering the quality of satellite communication in case of selected mobile terminals. It describes a measurement campaign carried out in varying urban environments, including a set of Android-powered smartphones coming from different manufacturers. Based on this, respective conclusions and remarks are given, which can aid consumers as well as device manufacturers and application developers.

scholarly journals GEODESIC METHODS FOR CREATION OF UNIQUE GEOINFORMATION SPACE

2019 ◽  
Vol 1 (1) ◽  
pp. 173-183
Author(s):  
Sergey Gorobtsov ◽  
Vladimir Obidenko
Keyword(s):  
Laser Scanning ◽  
Spatial Information ◽  
Survey Methods ◽  
Essential Element ◽  
Global Navigation Satellite Systems ◽  
3D Laser Scanning ◽  
Foreign Markets ◽  
Satellite Systems ◽  
Ground Survey ◽  
Global Navigation Satellite

Modern geodesic support is an integral and essential element of the process of collecting spatial information. The article considers geodesic methods for creating a unique geoinformation space: digitization of cartographic materials, ground survey methods (electronic total stations, 3D laser scanning), remote sensing and methods of the global navigation satellite systems GLONASS and GPS. The article also contains recommended conversion options between the coordinate systems SK-95 and GSK-2011. A comparative analysis of the surveyed geodesic methods for geodata col-lection was carried out. Russian and foreign markets of specialized software for processing geodata are considered, appropriate conclusions are made.

Assessment of geodetic products from MGEX analyses for the Onsala site

2020 ◽  
Author(s):  
Periklis-Konstantinos Diamantidis ◽  
Grzegorz Klopotek ◽  
Rüdiger Haas
Keyword(s):  
Global Navigation Satellite Systems ◽  
Observation Data ◽  
International Gnss Service ◽  
Satellite Systems ◽  
Troposphere Gradients ◽  
Combined Solution ◽  
Gnss Receivers ◽  
Global Navigation Satellite ◽  
Gnss Data

<div>The emergence of BeiDou and Galileo as operational Global Navigation Satellite Systems (GNSS), in addition to Global Positioning System (GPS) and GLONASS which are already in use, opens up possibilities in delivering geodetic products with higher precision. Apart from ensuring the homogeneity of the derived products, multi-GNSS analysis takes the advantage of new frequencies and an improved sky coverage. This should lead to better phase ambiguity resolution and an improved estimation of target parameters such as zenith wet delays (ZWD), troposphere gradients (GRD) and station positions. The International GNSS Service (IGS) has realised this potential by initiating the Multi-GNSS Experiment (MGEX) which provides orbit, clock and observation data for all operational GNSS. Correspondingly, the multi-technique space geodetic analysis software c5++ has been augmented with a MGEX-compliant GNSS module. Based on this new module and the Precise Point Positioning (PPP) approach using six-month of data, an assessment of the derived geodetic products is carried out for several GNSS receivers located at the Onsala core site. More specifically, we perform both single- and multi-GNSS data analysis using Kalman filter and least-squares methods and assess the quality of the derived station positions, ZWD and GRD. A combined solution using all GNSS together is carried out and the improvement with respect to station position repeatabilities is assessed for each station. Inter-system biases, which homogenise the different time scale that each GNSS operates in and are necessary for the multi-GNSS combination, are estimated and presented. Finally, the applied inter-system weighting is discussed as well as its impact on the derived geodetic products.</div>

scholarly journals GEOSPATIAL DATA QUALITY OF THE SERVIR CORS NETWORK

2015 ◽  
Vol II-3/W5 ◽  
pp. 285-290 ◽  
Author(s):  
J. Santos ◽  
R. Teodoro ◽  
N. Mira ◽  
V. B. Mendes
Keyword(s):  
Quality Control ◽  
Geospatial Data ◽  
Global Navigation Satellite Systems ◽  
Positional Accuracy ◽  
Worst Case ◽  
Static Mode ◽  
Satellite Systems ◽  
Gnss Positioning ◽  
Global Navigation Satellite

The SERVIR Continuous Operation Reference Stations (CORS) network was implemented in 2006 to facilitate land surveying with Global Navigation Satellite Systems (GNSS) positioning techniques. Nowadays, the network covers all Portuguese mainland. The SERVIR data is provided to many users, such as surveyors, universities (for education and research purposes) and companies that deal with geographic information. By middle 2012, there was a significant change in the network accessing paradigm, the most important of all being the increase in the responsibility of managing the network to guarantee a permanent availability and the highest quality of the geospatial data. In addition, the software that is used to manage the network and to compute the differential corrections was replaced by a new software package. These facts were decisive to perform the quality control of the SERVIR network and evaluate positional accuracy. In order to perform such quality control, a significant number of geodetic monuments spread throughout the country were chosen. Some of these monuments are located in the worst location regarding the network geometry in order to evaluate the accuracy of positions for the worst case scenarios. Data collection was carried out using different GNSS positioning modes and were compared against the benchmark positions that were determined using data acquired in static mode in 3-hour sessions. We conclude the geospatial data calculated and provided to the users community by the network is, within the surveying purposes, accurate, precise and fits the needs of those users.

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