A method to compare and improve land cover datasets: Application to the GLC-2000 and MODIS land cover products

This paper presents a methodology for the comparison of different land cover datasets and illustrates how this can be extended to create a hybrid land cover product. The datasets used in this paper are the GLC-2000 and MODIS land cover products. The methodology addresses: 1) the harmonization of legend classes from different global land cover datasets and 2) the uncertainty associated with the classification of the images. The first part of the methodology involves mapping the spatial disagreement between the two land cover products using a combination of fuzzy logic and expert knowledge. Hotspots of disagreement between the land cover datasets are then identified to determine areas where other sources of data such as TM/ETM images or detailed regional and national maps can be used in the creation of a hybrid land cover dataset

Probing the intrinsic state of a one-dimensional quantum well with a photon-assisted tunneling

The photon-assisted tunneling (PAT) through a single wall carbon nanotube quantum well (QW) under influence an external electromagnetic field for probing of the Tomonaga Luttinger liquid (TLL) state is suggested. The elementary TLL excitations inside the quantum well are density ($\rho_{\pm}$) and spin ($\sigma_{\pm}$) bosons. The bosons populate the quantized energy levels $\epsilon^{\rho +}_n =\Delta n/ g$ and $\epsilon^{\rho -(\sigma \pm)}_n = \Delta n$ where $\Delta = h v_F /L$ is the interlevel spacing, $n$ is an integer number, $L$ is the tube length, $g$ is the TLL parameter. Since the electromagnetic field acts on the $\rho_{+}$ bosons only while the neutral $\rho_{-}$ and $\sigma_{\pm}$ bosons remain unaffected, the PAT spectroscopy is able of identifying the $\rho_{+}$ levels in the QW setup. The spin $\epsilon_n^{\sigma+}$ boson levels in the same QW are recognized from Zeeman splitting when applying a d.c. magnetic field $H \neq 0$ field. Basic TLL parameters are readily extracted from the differential conductivity curves.Comment: 10 pages, 5 figure

Sources of Mycorrhizal Infection of Shorea Acuminata Seedlings Under Laboratory Conditions*)

Uninoculated dipterocarp seedlings raised in normal field soil in nurseries were always found to have mycorrhizas after a few months. This study set out to determine whether dipterocarp seedlings could continue to grow and develop in the absence of mycorrhizas and also to determine possible sources of mycorrhizal infection of dipterocarp seedlings raised under laboratory conditions using Shorea acuminata as a typical example. Seedlings were planted in capped or uncapped perspex boxes containing sterile or non-sterile field soil and watered daily with sterile water or tap water. Seedling growth and development of mycorrhizas were monitored at monthly intervals for up to seven months. Seedlings grown in sterile soil remained uninfected after seven months while infection was found in some of the seedlings grown in normal soil regardless of whether they had been watered with tap water or sterile water. This showed that field soil (i.e. under grass) far from the forest contained suitable inoculum for forest tree seedlings. Tap water and the air were not important sources of infection. However, mycorrhizal infection was very uneven indicating that the inoculum was probably very unevenly distributed in the soil or that the inoculum density was rather low. Seedlings grown in sterile soil showed better growth than those grown in normal soil and infection of roots by parasitic fungi in the latter was also observed

Network synchronization: Optimal and Pessimal Scale-Free Topologies

By employing a recently introduced optimization algorithm we explicitely design optimally synchronizable (unweighted) networks for any given scale-free degree distribution. We explore how the optimization process affects degree-degree correlations and observe a generic tendency towards disassortativity. Still, we show that there is not a one-to-one correspondence between synchronizability and disassortativity. On the other hand, we study the nature of optimally un-synchronizable networks, that is, networks whose topology minimizes the range of stability of the synchronous state. The resulting ``pessimal networks'' turn out to have a highly assortative string-like structure. We also derive a rigorous lower bound for the Laplacian eigenvalue ratio controlling synchronizability, which helps understanding the impact of degree correlations on network synchronizability.Comment: 11 pages, 4 figs, submitted to J. Phys. A (proceedings of Complex Networks 2007

The Role of Citizen Science in Earth Observation

Citizen Science (CS) and crowdsourcing are two potentially valuable sources of data for Earth Observation (EO), which have yet to be fully exploited. Research in this area has increased rapidly during the last two decades, and there are now many examples of CS projects that could provide valuable calibration and validation data for EO, yet are not integrated into operational monitoring systems. A special issue on the role of CS in EO has revealed continued trends in applications, covering a diverse set of fields from disaster response to environmental monitoring (land cover, forests, biodiversity and phenology). These papers touch upon many key challenges of CS including data quality and citizen engagement as well as the added value of CS including lower costs, higher temporal frequency and use of the data for calibration and validation of remotely-sensed imagery. Although still in the early stages of development, CS for EO clearly has a promising role to play in the future

The impact of contributor confidence, expertise and distance on the crowdsourced land cover data quality

There is much interest in the opportunities for formal scientific investigations afforded by crowdsourcing and citizen sensing activities. However, one of the critical research issues relates to the 'quality' of the data collected in this way. This paper uses volunteer data on land cover collected under the Geo-Wiki system, where contributors label the land cover class at a series of locations, with expert labels at the same locations. It examines the statistical relationships between the accuracy of volunteer labels, their self assessed confidence in labeling, their 'experiential distance' to the location under consideration and the level of their domain expertise. The results show that distance has a minor effect on the reliability of land cover labeling, and that generally expertise has a greater effect, but not for all landcover classes

Motivating and Sustaining Participation in VGI

Volunteers are the key component in the collection of Volunteered Geographic Information (VGI), so what motivates their participation, what strategies work in recruitment and how sustainability of participation can be achieved are key questions that need to be answered to inform VGI system design and implementation. This chapter reviews studies that have examined these questions and presents the main motivational factors that drive volunteer participation, as determined from empirical research. Some best practices from broader citizen science applications are also presented that may have relevance for VGI initiatives. Finally, a set of case studies from our experiences are used to illustrate how volunteers have been motivated to collect VGI through mapping parties, gamification and working with schools

Editorial: The rise of collaborative mapping: Trends and future directions

The nature of map production and the dissemination of spatially referenced information have changed radically over the last decade. This change has been marked by an explosion of user generated spatial content via Web 2.0, access to a rising tide of big data streams from remotely-sensed and public data archives, and the use of mobile phones and other sensors as mapping devices. All of these developments have facilitated a much wider use of geodata, transforming ordinary citizens into neogeographers. This increase in user-generated content has resulted in a blurring of the boundaries between the traditional map producer, i.e., national mapping agencies and local authorities, and citizens as consumers of this information. Citizens now take an active role in mapping different types of features on the Earth's surface as volunteers, either by providing observations on the ground or tracing data from other sources, such as aerial photographs or satellite imagery. OpenStreetMap (OSM) and Ushahidi are two well-known examples of a growing collection of collaborative mapping communities that are building rich spatial datasets, which are openly accessible