Paolo Dabove

Indoor navigation using Smartphone technology: A future challenge or an actual possibility?

Today knowing where we are has become an important issue for people who interactively and dynamically live and work in urban cities. Each user has a very complete and complex set of technologies for positioning and navigating in his/her hands which are simple to use even if they are not good at positioning or in Geomatics. Accelerometers, gyroscopes, magnetometers, pressure sensors, GNSS receivers, digital cameras are all tools which can be used for defining a three-dimensional position and their integration could be the key point of this technology. Indoor positioning is the latest challenge to be used whenever GNSS positioning is not always available or null, even using high sensitivity sensors. An alternative solution must be found starting from determining the other available solutions in Smartphone devices. An example of indoor positioning could be obtained by using the Image Based Navigation (IBN) approach, where the coordinates of our device are defined using the photogrammetric principle. Several papers demonstrate that IBN can be an useful approach for positioning and how the device in Smartphones can work indoors. In this study, the authors attempt to combine the IBN method with the potentiality of Smartphone internal sensors, in order to verify their performance in indoor positioning.

Achievable Positioning Accuracies in a Network of GNSS Reference Stations

The Network Real Time Kinematic (NRTK) positioning is nowadays a very common practice not only in academia but also in the professional world. Since its appearance, over 10 years ago, a growing number of people use this type of positioning not only for topographic applications, but also for the control of vehicles fleets, precision agriculture, land monitoring, etc.. To support these users several networks of Continuous Operating Reference Stations (CORSs) were born. These networks offer real-time services for NRTK positioning, providing a centimetric positioning accuracy with an average distance of 25-35 kms between the reference stations.

Augmented positioning with CORSs network services using GNSS mass-market receivers

Over the last twenty years, positioning with low cost GNSS sensors has become widespread worldwide at both commercial and academic level. The Geomatics Research Group of DIATI at the Politecnico di Torino has carried out several experiments in order to evaluate the precision achievable when using mass-market GNSS receivers with a network of permanent GNSS station (also called CORSs network - Continuous Operating Reference Stations) for various purposes. The aim of this study is to investigate real effect and the role of the CORSs Network for this type of receivers, and especially how the products generated by the CORSs network can be used to improve the level of accuracy and precision if mass-market receivers are considered. The rapid development and diffusion of the GNSS network which provides a positioning service has enabled us to use single frequency receivers both in post-processing and real time approach by means of virtual RINEX and differential corrections. In the first approach, in order to determine the possible level of accuracy and precision obtainable with this sensor, a special test field was carried out which enabled us to study the variation of position with millimetrical accuracy. Tests were carried out considering various types of receivers (geodetic and mass market) and antennas (patch and geodetic) in static mode. The static test was carried out by acquiring raw data for 24 hours and dividing them into small parts (5, 10 or 15 minutes each), in order to consider the effect of the acquisition time on the final results and also consider the complete constellation. The postprocessing was performed with a commercial software. An interesting advantage is the possibility of generating a VR close to the rover position especially when mass market sensors are used, with the aim of creating a short (few meters) baseline, or in extreme cases it is possible to realize a null baseline thus eliminating the bias with the double differences in a relative positioning. By using a VR we obtain an independent solution in respect to the master-rover distance in attempt of fixing the ambiguity phase. The real-time experience was carried out with mass-market receivers for NRTK (Network Real Time Kinematic) positioning within the Regione Piemonte CORSs network. Two network products were used (VRS® and nearest correction): RTKLIB software was used in order to apply these corrections to the raw data of the mass market receivers. Some very good results were obtained which are reported in this paper.

Kalman Filter as Tool for the Real-time Detection of Fast Displacements by the Use of Low-cost GPS Receivers

In this paper the problem of landslide monitoring and deformation analysis using the Kalman filter and results obtained from a GPS mass-market receiver in real-time is addressed. Landslide monitoring and deformation analysis are relevant aspects about the safety of human life in any terrain where landslides can impact human activity. It is therefore necessary to monitor these effects in order to detect and prevent these risks. Very often, most of this type of monitoring is carried out by using traditional topographic instruments (e.g. total stations) or satellite techniques such as GNSS receivers, and many experiments were carried out considering these types of mass-market instruments. In this context it is fundamental to detect whether or not deformation exists, in order to predict future displacement. Filtering means are essential to process the diverse noisy measurements (especially if low cost sensors are considered) and estimate the parameters of interest. In this paper a particu lar version of Kalman Filter is considered in order to understand if there are any displacements from a statistical point of view in real time. The tests, the algorithm and results are herein reported.

GPS mass-market receivers for precise farming

The use of Global Navigation Satellite Systems (GNSS) can help farmers become more efficient, reduce their use of chemicals, and increase crop yields. By increasing the accuracy, availability, reliability and continuity of satellite signals, the use of some augmentations systems (such as WAAS or EGNOS or other private systems) will remove some of the barriers to the adoption of precision agriculture, also not only considering geodetic receivers and complex systems of navigation. The goal of this work is to show how it is possible to consider both mass-market receivers and antennas to obtain centimetrical accuracies, useful for many precise farming applications. As it is possible to find in bibliography, the accuracy of real-time positioning depends mainly on the type of receiver (whether it is single frequency or low-cost) and antenna (whether it is patch, mass-market or geodetic) used. Some different receivers and antennas were tested and some results can be shown, not to analyze what receiver or antenna is the best but in order to analyze the state of the art of these type of instruments. The NRTK experiences have been conducted using mass-market receivers (mainly u-blox) within the Regione Piemonte network of permanent stations. Good results have been obtained: in fact, despite a single frequency instrument is used, the horizontal and vertical components have centimetrical level of accuracy. The maximum 2D error in the case of `fix positioning is always less than 5 cm, precision required in many applications of precise farming, such as to individuate livestock positioning and fencing or for crop cultivation (e.g. cereals) and other low-accuracy operations (fertilising and reaping). Practical experiences have demonstrated the value of precise navigation and guidance technologies to increase yield and efficiency of agricolture operations and we want to show it in this paper. Under this condition, mass market sensors could be a valid instruments for a large part of surveying applications related to precise farming.

Analysis of Ambiguity False Fixing within a GBAS

Since the first appearance of satellite positioning systems, GNSS positioning has become a standard and common practice. It is available in most parts of the territory of many nations. So, it is necessary to focus attention not on the feasibility of the positioning itself but on its quality control. In particular, we focus attention on the NRTK (Network Real Time Kinematic) positioning of a geodetic receiver into a network of permanent stations, the CORS (Continuous Operating Reference Stations) network. The goal of the survey is to obtain a centimetre accuracy, which is usually achieved after a correct fixing of the ambiguity phase. For various reasons, however, it may be possible that the fixing of the integer ambiguities in the receiver can be unreliable. Although the number of false fixes of the ambiguity is limited, it is necessary to minimize these events, or to know some available control parameters needed to alert the user when this eventuality is likely

Network Real Time Kinematic (NRTK) Positioning - Description, Architectures and Performances

In this last years, the differential GNSS positioning has had an intensive expansion, especially due to the development and realization of GNSS CORSs (Continuous Operating Reference Stations) networks. One of the main goals of these networks is to give the possibility to the users to extend the differential positioning (whether in real time or post-processing) up to 25-50 km, allowing a positioning useful for applications such as surveying, monitoring and precise navigation. It is possible to find in bibliography some studies that shown the performances of this type of positioning, with their limitations and peculiarities, also in function of the network size. The Network Real Time Kinematic (NRTK) positioning is a very common practice not only in academia but also in the professional world. Since its appearance, over 10 years ago, a growing number of people use this type of positioning not only for topographic applications, but also for the control of vehicles fleets, precision agriculture, land monitoring, etc. This chapter wants try to focus the attention on the methods and characteristics of NRTK positioning and to summarize principles and peculiarities of this type of GNSS positioning: the goal is to show how networks for NRTK positioning work and also to show the differential corrections that are available today, with their performances in order to obtain acceptable results, always considering the accuracy required by the purposes described above. So, first of all the GNSS network positioning will be discussed, starting from the network biases estimation to the rover positioning with particular attention to the differential GNSS corrections such as the Master Auxiliary Concept (MAC), Virtual Reference Station (VRS) and Flachen Korrektur Parameter (FKP). Particular attention will be also devoted both to the transmission of the differential corrections and their problems, such as the GSM coverage, and to the analysis of the RTCM protocol. A theoretical description of the network calculation and biases interpolation will be made and brief results for each correction will be shown, in order to give a practical example