The usability of GNSS mass-market receivers for cadastral surveys considering RTK and NRTK techniques

Nowadays many positioning techniques and methods are applied to the cadastral surveys. Starting from last decade, GPS/GNSS positioning had become one of the most used methodology thanks to the rapid development of satellite-based positioning and to the appearance of GNSS mass-market receivers and antennas. Methods based on these instruments are more affordable than the conventional ones even if their use for precise positioning is not so intuitive. This study is aimed to evaluate the use of single-frequency GPS/GNSS mass-market receivers for cadastral surveys, considering both single-base Real-Time Kinematic (RTK) and Network Real-Time Kinematic (NRTK) methodologies. Furthermore, a particular tool for predicting and estimating the occurrence of false fix of the phase ambiguities has been considered, in order to improve the accuracy and precision of the solutions. Considering the single-base positioning, the research results showed the difference of a few centimetres between the reference coordinates and the estimated ones if the distance between master and rover is less than 3 km, while considering the network positioning and the Virtual Reference Station correction, the difference are about a couple of centimetres for East and North component, and about 5 cm for the Up. Keywords: GNSS, Cadastral surveying, RTK, NRTK positioning, Mass-market receiver

The use of smartphone in the 21st century

Smartphone devices are nowadays common affordable devices not only for communication purposes but also for determining the user’s position, for sending emails, managing digital agendas and to allow internet access. Starting from last decade, they become interesting instruments also for engineering and biomedical applications, thanks to their high diffusion. In 2018, 66% of individuals in 52 key countries owned a smartphone, with an increment of about 3% in only one year. This fact permitted the rapid development of apps for different goals, starting from precise positioning both in outdoor and indoor scenarios, to the 3D reconstruction of the environment using images up to driving evaluation purposes or healthcare and biomedical engineering applications. This chapter resumes the main research fields where smartphone devices are considered, providing the main references. It also introduces and briefly describes the contributions contained in this book, guiding the reader through the logical structure of the book in order to point out new possible studies and future perspectives in different reserch fields

Single-frequency receivers as master permanent stations in GNSS networks: precision and accuracy of the positioning in mixed networks

The use of GPS/GNSS instruments is a common practice in the world at both a commercial and academic research level. Since last ten years, Continuous Operating Reference Stations (CORSs) networks were born in order to achieve the possibility to extend a precise positioning more than 15 km far from the master station. In this context, the Geomatics Research Group of DIATI at the Politecnico di Torino has carried out several experiments in order to evaluate the achievable precision obtainable with different GNSS receivers (geodetic and mass-market) and antennas if a CORSs network is considered. This work starts from the research above described, in particular focusing the attention on the usefulness of single frequency permanent stations in order to thicken the existing CORSs, especially for monitoring purposes. Two different types of CORSs network are available today in Italy: the first one is the so called “regional network” and the second one is the “national network”, where the mean inter-station distances are about 25/30 and 50/70 km respectively. These distances are useful for many applications (e.g. mobile mapping) if geodetic instruments are considered but become less useful if mass-market instruments are used or if the inter-station distance between master and rover increases. In this context, some innovative GNSS networks were developed and tested, analyzing the performance of rover’s positioning in terms of quality, accuracy and reliability both in real-time and post-processing approach. The use of single frequency GNSS receivers leads to have some limits, especially due to a limited baseline length, the possibility to obtain a correct fixing of the phase ambiguity for the network and to fix the phase ambiguity correctly also for the rover. These factors play a crucial role in order to reach a positioning with a good level of accuracy (as centimetric o better) in a short time and with an high reliability. The goal of this work is to investigate about the real effect and how is the contribute of L1 mass-market permanent stations to the CORSs Network both for geodetic and low-cost receivers; in particular is described how the use of the network products which are generated by the network (in real-time and post-processing) can improve the accuracy and precision of a rover 5, 10 and 15 km far from the nearest station. Some tests have been carried out considering different types of receivers (geodetic and mass market) and antennas (patch and geodetic). The tests have been conducted considering several positioning approaches (static, stop and go and real time) in order to make the analysis more complete. Good and interesting results were obtained: the followed approach will be useful for many types of applications (landslides monitoring, traffic control), especially where the inter-station distances of GNSS permanent station are greater than 30 km

New geomatics techniques for bees monitoring: the BEEMS project

Bees provide essential pollination services to natural ecosystems and agricultural crops. However, bee populations, both wild and farmed, are in decline around the world. To better manage and restore bee populations, long-term monitoring programs are needed. Direct monitoring of bees is expensive, time-consuming and requires a high level of expertise. Therefore, economic indicators for bee diversity and community composition are essential. The BEEMS Project, a project of Scientific and Technological Cooperation between Italy and Israel (Scientific Track 2019), aims to evaluate the cost-benefit ratio of new aerial Geomatics techniques compared to classical terrestrial methods to collect biotic and abiotic indicators of diversity bees and the composition of their communities. This work aims to present the project's progress, focusing on the Geomatics techniques applied to collect environmental data and produce spatial information useful for the work's progress

Technology as a tool to study visitor behaviour in museums: positioning and neuropsychological detection to identify physical & cognitive barriers

Inclusive communication projects in museums and cultural sites often start from generically applicable assumptions referring to the principles of accessible and inclusive design, without considering the peculiarities of a cultural experience. It therefore seems important to study the audiences’ behaviour in museums, with particular attention to the different types of visitors: regular audiences with appropriate backgrounds; occasional audiences with very different backgrounds; and disaffected audiences who do not consider cultural experiences important or rewarding. It is precisely the latter that an inclusive design must carefully target, with the aim of understanding the reason for this exclusion and thus overcoming it, hence it is important that such studies do not observe only the first two types of audience, whereas this is often the case. In this context, precise positioning is mandatory: in case of museums, it is necessary to determine users’ location at every epoch, with high sampling rate, to monitor movements, times and stops of the public within the museum, in relation to the exhibits, the spatial features of the rooms, and the communication and display solutions, relating them to information resulting from ad hoc surveys. From the positioning point of view, one of the main problems is represented in tracking people in indoor environments, where the GNSS is not available, and there are often cramped spaces. Besides, if the number of people to be tracked is high, the level of difficulties increases dramatically. The problem of positioning even large numbers of people within closed and delimited spaces presents some difficulties and technical criticalities. On the other hand, the restitution of such data requires accentuated reliability: the behaviour and reactions recorded in the public during the experiment must be related to precise spatial positions, since the emotional responses of the public can vary in a very short time. At present, the research group is studying and implementing new technologies available in mobile devices, such as Ultra Wide Band (UWB) technology, to study individual visiting experiences. The technological challenge in these contexts goes beyond mere technical effectiveness. Indeed, the instrumentation required to track individual visitors, in certain solutions, risks influencing people’s behaviour because it is moderately ostrusive: conversely, the challenge at present is to integrate the various sensing devices into compact and unobtrusive soluti- ons. The Authors have implemented a Python code on a portable Raspberry device that guarantees the users’ location by exploiting signals coming from beacon devices. Communication systems between the device detecting neurophysiological reactions and monitoring physical movements can be implemented and optimised, fusing this technology with another one related to positioning purposes, exploiting electromagnetic signals such as ultra-wide-band technologies or Bluetooth, which guarantees the possibility of reaching positioning solutions even in indoor environments without afflicting the signals for neurophysiological parameter estimations

Inertial sensors for smartphones navigation

The advent of smartphones and tablets, means that we can constantly get informa- tion on our current geographical location. These devices include not only GPS/GNSS chipsets but also mass-market inertial platforms that can be used to plan activities, share locations on social networks, and also to perform positioning in indoor and outdoor scenarios. This paper shows the performance of smartphones and their inertial sensors in terms of gaining information about the user’s current geographical loca- tion considering an indoor navigation scenario. Tests were carried out to determine the accuracy and precision obtainable with internal and external sensors. In terms of the attitude and drift estimation with an updating interval equal to 1 s, 2D accuracies of about 15 cm were obtained with the images. Residual benefits were also obtained, however, for large intervals, e.g. 2 and 5 s, where the accuracies decreased to 50 cm and 2.2 m, respectively

Towards the Monitoring of Underground Caves Using Geomatics and Geophysical Techniques: 3D Analyses and Seismic Response

Analyses of climate change, due to its impact not only on the weather and the environment but also on human health and life, are one of the most important study activities made in recent years. There is relatively high confidence that glacial melt and heavy rainfall events will continue to increase. These climate-related events carry a microseismic signature that can guide monitoring activities. In the last decade, there have been growing applications of long-term continuous ambient seismic noise systems to monitor landslides and potentially unstable rock sites. This work reports some of the activities made during a project performed under the Department of Excellence on Climate Change (2018–2022), funded by the Italian Ministry for University and Research (MUR), in order to improve environmental seismic analyses. The selected test site is the Bossea Cave (NW Italy), where two seismic stations were installed. The goals were to use these stations to understand and study climate change events above the Bossea Cave, analyzing the data from a geophysical and geomatics point of view. Starting with UAV flights and photogrammetric processing to obtain a 3D model of the cave, both ambient seismic noise and microseismicity analyses highlighted an important effect of air temperature and precipitation on the seismic response of the monitored rock mass overlying the Bossea Cave. In particular, a clear effect on the ambient seismic noise spectral content and the peak frequency of the microseismic events driven by temperature and precipitation was found during the warmer monitoring months, with almost zero delays in the seismic response. This is a preliminary but important study, even if longer monitoring data and thermal modeling efforts are needed to fully understand this seasonal variation

Assessment of positioning performances in Italy from GPS, BDS and GLONASS constellations

The use of multiple GNSS constellations has been beneficiary to positioning performances and reliability in recent times, especially in low cost mass-market setups. Along with GPS and GLONASS, GALILEO and BDS are the other two constellations aiming for global coverage. With ample research demonstrating the benefits of GALILEO in the European region, there has been a lack of study to demonstrate the performance of BDS in Europe, especially with mass-market GNSS receivers. This study makes a comparison of the performances between the combined GPS-GLONASS and GPS-BDS constellations in Europe with such receivers. Static open sky and kinematic urban environment tests are performed with two GNSS receivers as master and rover at short baselines and the RTK and double differenced post processed solutions are analyzed. The pros and cons of both the constellation choices is demonstrated in terms of fixed solution accuracies, percentage of false fixes, time to first fix for RTK and float solution accuracies for post processed measurements. Centimeter level accuracy is achieved in both constellations for static positioning with GPS-BDS combination having a slightly better performance in comparable conditions and smaller intervals. GPS-GLONASS performed slightly better for longer intervals due to the current inconsistent availability of BDS satellites. Even if the static tests have shown a better performance of GPS-BDS combination, the kinematic results show that there are no significant differences between the two tested configurations. Keywords: GNSS, BDS, GLONASS, NRTK positioning, Accurac

Real-time monitoring for fast deformations using GNSS low-cost receivers

Landslides are one of the major geo-hazards which have constantly affected Italy especially over the last few years. In fact 82% of the Italian territory is affected by this phenomenon which destroys the environment and often causes deaths: therefore it is necessary to monitor these effects in order to detect and prevent these risks. Nowadays, most of this type of monitoring is carried out by using traditional topographic instruments (e.g. total stations) or satellite techniques such as global navigation satellite system (GNSS) receivers. The level of accuracy obtainable with these instruments is sub-centimetrical in post-processing and centimetrical in real-time; however, the costs are very high (many thousands of euros). The rapid diffusion of GNSS networks has led to an increase of using mass-market receivers for real-time positioning. In this paper, the performances of GNSS mass-market receiver are reported with the aim of verifying if this type of sensor can be used for real-time landslide monitoring: for this purpose a special slide was used for simulating a landslide, since it enabled us to give manual displacements thanks to a micrometre screw. These experiments were also carried out by considering a specific statistical test (a modified Chow test) which enabled us to understand if there were any displacements from a statistical point of view in real time. The tests, the algorithm and results are reported in this paper