Why GPS makes distances bigger than they are

Global Navigation Satellite Systems (GNSS), such as the Global Positioning System (GPS), are among the most important sensors for movement analysis. GPS is widely used to record the trajectories of vehicles, animals and human beings. However, all GPS movement data are affected by both measurement and interpolation error. In this article we show that measurement error causes a systematic bias in distances recorded with a GPS: the distance between two points recorded with a GPS is -- on average -- bigger than the true distance between these points. This systematic `overestimation of distance' becomes relevant if the influence of interpolation error can be neglected, which is the case for movement sampled at high frequencies. We provide a mathematical explanation of this phenomenon and we illustrate that it functionally depends on the autocorrelation of GPS measurement error ($C$). We argue that $C$ can be interpreted as a quality measure for movement data recorded with a GPS. If there is strong autocorrelation any two consecutive position estimates have very similar error. This error cancels out when average speed, distance or direction are calculated along the trajectory. Based on our theoretical findings we introduce a novel approach to determine $C$ in real-world GPS movement data sampled at high frequencies. We apply our approach to a set of pedestrian and a set of car trajectories. We find that the measurement error in the data is strongly spatially and temporally autocorrelated and give a quality estimate of the data. Finally, we want to emphasize that all our findings are not limited to GPS alone. The systematic bias and all its implications are bound to occur in any movement data collected with absolute positioning if interpolation error can be neglected.Comment: 17 pages, 8 figures, submitted to IJGI

Social dimensions of a forest-based bioeconomy : A summary and synthesis

How perceptions of the forest-based bioeconomy differ across country contexts and social groups is important as it opens possibilities for the development of more inclusive, locally and socially relevant bioeconomy policies and strategies. Therefore, this special section explores the social dimensions of the forest-based bioeconomy by focusing on discourses and perceptions of different actor groups in Europe. We introduce six articles that range from review and discursive approaches to consumer studies. The section adds to the existing literature by focusing not only on political decision makers, stakeholders, and experts but also on the public, media and students. Patterns in the presented discourses and perceptions can be identified but more is needed to validate these and respond to the question of representativeness.Peer reviewe

Inferring the history of spatial diffusion processes (Short Paper)

When studying the spatial diffusion of a phenomenon, we often know its geographic distribution at one or more snapshots in time, while the complete history of the diffusion process is unknown. For example, we know when and where the first Indo-European languages arrived in South America and their current distribution. However, we do not know the history of how these languages spread, displacing the indigenous languages from their original habitat. We present a Bayesian model to interpolate the history of a diffusion process between two points in time with known geographical distributions. We apply the model to recover the spread of the Indo-European languages in South America and infer a posterior distribution of possible evolutionary histories of how they expanded their areas since the time of the first invasion by Europeans. Our model is more generally applicable to infer the evolutionary history of geographic diffusion phenomena from incomplete data

Improving the accuracy of estimates of animal path and travel distance using GPS drift-corrected dead reckoning

Route taken and distance travelled are important parameters for studies of animal locomotion. They are often measured using a collar equipped with GPS. Collar weight restrictions limit battery size, which leads to a compromise between collar operating life and GPS fix rate. In studies that rely on linear interpolation between intermittent GPS fixes, path tortuosity will often lead to inaccurate path and distance travelled estimates. Here, we investigate whether GPS‐corrected dead reckoning can improve the accuracy of localization and distance travelled estimates while maximizing collar operating life. Custom‐built tracking collars were deployed on nine freely exercising domestic dogs to collect high fix rate GPS data. Simulations were carried out to measure the extent to which combining accelerometer‐based speed and magnetometer heading estimates (dead reckoning) with low fix rate GPS drift correction could improve the accuracy of path and distance travelled estimates. In our study, median 2‐dimensional root‐mean‐squared (2D‐RMS) position error was between 158 and 463 m (median path length 16.43 km) and distance travelled was underestimated by between 30% and 64% when a GPS position fix was taken every 5 min. Dead reckoning with GPS drift correction (1 GPS fix every 5 min) reduced 2D‐RMS position error to between 15 and 38 m and distance travelled to between an underestimation of 2% and an overestimation of 5%. Achieving this accuracy from GPS alone would require approximately 12 fixes every minute and result in a battery life of approximately 11 days; dead reckoning reduces the number of fixes required, enabling a collar life of approximately 10 months. Our results are generally applicable to GPS‐based tracking studies of quadrupedal animals and could be applied to studies of energetics, behavioral ecology, and locomotion. This low‐cost approach overcomes the limitation of low fix rate GPS and enables the long‐term deployment of lightweight GPS collars

Developing future visions for bio-plastics substituting PET – a backcasting approach

The demand for plastics far exceeds that for any other bulk material and is expected to grow further due to global economic and population growth. Packaging is by far the largest end-user segment for plastics. Interest in bioplastics is increasing as public awareness of plastic waste accumulation in natural environ- ments increases. 2,5-Furandicarboxylic acid (FDCA) is the key monomer in the production of polyethylene 2,5-furandicarboxylate (PEF), a polymer that offers a sustainable solution to replace the commonly used polymer polyethylene terephthalate (PET). A backcasting workshop with 42 experts was held to identify current barriers and challenges that block the commercialization of FDCA-based products and to outline potential pathways toward future market diffusion. Several barriers which are strongly related to techno- logical and market-related aspects are preventing the full potential of FDCA from being unlocked. FDCA products cited in the literature are versatile and cover a wide array of niche applications. In the back- casting workshop, participants described their specific – yet highly divergent – future visions for PEF. Participants with a background in FDCA production referred mostly to developments that would need to take place in the field of FDCA applications to turn their vision into reality, while participants with a background in FDCA product development tended to refer to open issues related to FDCA synthesis. The findings of this study indicate that there is a great need for intensified cross-disciplinary communication and collaboration.publishe

Forest sector sustainability communication in Europe : A systematic literature review on the contents and gaps

Purpose of review Stakeholder communication plays an important role in enhancing the societal sustainability and business acceptability of the forest sector. The purpose of this study is to present the current state of forest-sector communication research with its stakeholders at different hierarchical levels of sustainability (i.e., societal, sectorial, corporate and product sustainability) in Europe. Recent findings A systematic literature review was implemented to acquire information on the research outcomes related to sustainability communication between the forest sector and different stakeholders presented in international peer-reviewed journals between 2005 and 2015. The examined literature emphasizes the role of stakeholder communication for forest sector sustainability and acceptability, but no specific information seems to exist on how to communicate and build the forest sector image in the eyes of different stakeholders. Summary The gap in the research information indicates there is a need for more theoretical and empirical work on communication and image building processes by, e.g., recognizing the specific communication needs of different stakeholders via two-way and proactive information exchange. In the development process of forest sector communication and image building, more efforts on sending well-specified messages for well-targeted audiences should be made.Peer reviewe

Contact-tracing in cultural evolution: a Bayesian mixture model to detect geographic areas of language contact

Horizon 2020(H2020)818854Descriptive and Comparative Linguistic

Exploring correlations in genetic and cultural variation across language families in northeast Asia

Culture evolves in ways that are analogous to, but distinct from, genomes. Previous studies examined similarities between cultural variation and genetic variation (population history) at small scales within language families, but few studies have empirically investigated these parallels across language families using diverse cultural data. We report an analysis comparing culture and genomes from in and around northeast Asia spanning 11 language families. We extract and summarize the variation in language (grammar, phonology, lexicon), music (song structure, performance style), and genomes (genome-wide SNPs) and test for correlations. We find that grammatical structure correlates with population history (genetic history). Recent contact and shared descent fail to explain the signal, suggesting relationships that arose before the formation of current families. Our results suggest that grammar might be a cultural indicator of population history while also demonstrating differences among cultural and genetic relationships that highlight the complex nature of human history.Introduction Results Discussion Material and Methods - Experimental design - Statistical analysi