Improving merge methods for grid-based digital elevation models

Digital Elevation Models (DEMs) are used to represent the terrain in applications such as, for example, overland flow modelling or viewshed analysis. DEMs generated from digitising contour lines or obtained by LiDAR or satellite data are now widely available. However, in some cases, the area of study is covered by more than one of the available elevation data sets. In these cases the relevant DEMs may need to be merged. The merged DEM must retain the most accurate elevation information available while generating consistent slopes and aspects. In this paper we present a thorough analysis of three conventional grid-based DEM merging methods that are available in commercial GIS software. These methods are evaluated for their applicability in merging DEMs and, based on evaluation results, a method for improving the merging of grid-based DEMs is proposed. DEMs generated by the proposed method, called Id:Blend, showed significant improvements when compared to DEMs produced by the three conventional methods in terms of elevation, slope and aspect accuracy, ensuring also smooth elevation transitions between the original DEMs. The results produced by the improved method are highly relevant different applications in terrain analysis, e.g., visibility, or spotting irregularities in landforms and for modelling terrain phenomena, such as overland flow

Scale‐dependent strategies for coexistence of mesocarnivores in human‐dominated landscapes

publishedVersio

Exploring the potential of Google Earth as a communication and engagement tool in collaborative Natural Flood Management planning

This paper considers the development and evaluation of a Google Earth “virtual globe” tour for communicating spatial data and engaging stakeholders in the early stages of a natural flood management (NFM) planning scenario, using a rural UK river catchment that suffered significant flooding in 2007. With a range of diverse stakeholder interests to consider, early engagement and the development of trust before decision‐making are essential for the long‐term success of such catchment‐wide projects. A local catchment group was consulted to identify key information requirements, and from this a “virtual globe” tour was created. The process involved specialist skills and expert leadership, but the end result was accessible to a range of audiences. User evaluation indicated that it was easy to navigate and can be used to stimulate interest and engage stakeholders. Participants trusted the content and valued the interactivity of the tour. It was helpful for communicating and educating participants about the catchment, the issues it faces, and the potential to incorporate NFM, particularly for those with little or no prior knowledge. More abstract information was harder to convey and there were limitations in the availability of suitable data for some variables and the in quality of satellite imagery. This exploratory research found that a Google Earth “virtual globe” tour can be a valuable tool in the initial stages of an NFM project, but there are also opportunities to use this technique in the more advanced stages of the planning process. The approach could be used as part of a wider toolkit for communication and engagement and has potential as a decision support tool in other environmental management scenarios with requirements for public participation, enabling the views of a range of participants to be captured through online distribution and to generate discussion in workshop setting

Patterns of modern pollen and plant richness across northern Europe

Sedimentary pollen offers excellent opportunities to reconstruct vegetation changes over past millennia. Number of different pollen taxa or pollen richness is used to characterise past plant richness. To improve the interpretation of sedimentary pollen richness, it is essential to understand the relationship between pollen and plant richness in contemporary landscapes. This study presents a regional-scale comparison of pollen and plant richness from northern Europe and evaluates the importance of environmental variables on pollen and plant richness. We use a pollen dataset of 511 lake-surface pollen samples ranging through temperate, boreal and tundra biomes. To characterise plant diversity, we use a dataset formulated from the two largest plant atlases available in Europe. We compare pollen and plant richness estimates in different groups of taxa (wind-pollinated vs. non-wind-pollinated, trees and shrubs vs. herbs and grasses) and test their relationships with climate and landscape variables. Pollen richness is significantly positively correlated with plant richness (r = 0.53). The pollen plant richness correlation improves (r = 0.63) when high pollen producers are downweighted prior to estimating richness minimising the influence of pollen production on the pollen richness estimate. This suggests that methods accommodating pollen-production differences in richness estimates deserve further attention and should become more widely used in Quaternary pollen diversity studies. The highest correlations are found between pollen and plant richness of trees and shrubs (r = 0.83) and of wind-pollinated taxa (r = 0.75) suggesting that these are the best measures of broad-scale plant richness over several thousands of square kilometres. Mean annual temperature is the strongest predictor of both pollen and plant richness. Landscape openness is positively associated with pollen richness but not with plant richness. Pollen richness values from extremely open and/or cold areas where pollen production is low should be interpreted with caution because low local pollen production increases the proportion of extra-regional pollen. Synthesis. Our results confirm that pollen data can provide insights into past plant richness changes in northern Europe, and with careful consideration of pollen-production differences and spatial scale represented, pollen data make it possible to investigate vegetation diversity trends over long time-scales and under changing climatic and habitat conditions.Peer reviewe

Development and evaluation of a method to estimate the potential of decarbonisation technologies deployment at higher education campuses

peer-reviewedThis paper describes a method for the quantitative estimation of the potential of decarbonisation technologies deployed on Higher Education Campuses (HEC). This was developed to fill the need for a practicable and standardised method to provide preliminary estimations of the deployment potential of building integrated photovoltaics (PV), micro-wind turbines, rainwater harvesting and ground mounted PV at HECs. The method identifies two key variables, namely roof area and open carpark area, to aid estimation of decarbonisation technologies deployment at HECs, using Google Earth imagery coupled with publicly available online HEC maps. The method was trialled for the higher education sector in Ireland identifying major potential for deployment of decarbonisation technologies for the sector. The building decarbonisation aspect of the proposed approach is applicable to sectors outside HEC particularly commercial and industrial sectors due to similarity in building footprint characteristics. The open carpark component of the methodology is also applicable to city-scale analysis due to uniformity in form of open carparks worldwide. This highlights the usefulness of this method through informing city-scale transitions towards decarbonisatio

Land reclamation and artificial islands: Walking the tightrope between development and conservation

Coastal developments worldwide have put entire shoreline ecosystems at risk. Recently, land reclamation has been extended to the construction of whole new islands; a phenomenon that is particularly common in Asia and the Middle East and is recognised as a global conservation issue. Using Penang Island, Malaysia as a case study, we illustrate the relationship between rapid population growth and the simultaneous increase in urbanisation, land reclamation and extent of artificial shorelines; and decrease in the quality and extent of natural coastal habitats. Our goal was to provide an up-to-date assessment of the state of coastal habitats around Penang, identify knowledge gaps and identify locations that may be potentially suitable for eco-engineering. Comparisons of historical and current topographic maps revealed that land formerly consisting of coastal swamp and forest, mangrove forests, sandy beaches, and rubber and oil plantations have been lost to large-scale land reclamation and urbanisation. Between 1960 and 2015, there were increases in urbanised area, reclaimed land, and artificial shoreline extent. The total extent of mangrove forests has remained relatively stable but this balance is characterised by significant losses on the east coast coupled with increases on the west coast. Coastal development on the island is still on-going with plans for the construction of five artificial islands and another two coastal reclamation projects are either underway or scheduled for the near future. If the plans for future land reclamations are fully realized, 32.3 km2 of the 321.8 km2 island (10%) will be reclaimed land and the associated negative effects on the island’s natural coastal habitats will be inevitable. This study highlights sections of the coast of Penang Island in need of effective monitoring, conservation and management and explores the possibility of incorporating ecological engineering into development projects, either prospectively or retrospectively, to create more environmentally-friendly urban environments and to promote educational, amenity and economic activities. With coastal development taking place on a global scale, opportunities to balance development needs with conservation strategies abound and should be integrated into present and subsequent projects to protect these coastal ecosystems for future generations

Determining relative bulk viscosity of kilometre-scale crustal units using field observations and numerical modelling

Though the rheology of kilometre-scale polymineralic rock units is crucial for reliable large-scale, geotectonic models, this information is difficult to obtain. In geotectonic models, a layer is defined as an entity at the kilometre scale, even though it is heterogeneous at the millimetre to metre scale. Here, we use the shape characteristics of the boundaries between rock units to derive the relative bulk viscosity of those units at the kilometre scale. We examine the shape of a vertically oriented ultramafic, harzburgitic-lherzolitic unit, which developed a kilometre-scale pinch and swell structure at mid-crustal conditions (~ 600 °C, ~ 8.5 kbar), in the Anita Shear Zone, New Zealand. The ultramafic layer is embedded between a typical polymineralic paragneiss to the west, and a feldspar-quartz-hornblende orthogneiss, to the east. Notably, the boundaries on either side of the ultramafic layer give the ultramafics an asymmetric shape. Microstructural analysis shows that deformation was dominated by dislocation creep (n = 3). Based on the inferred rheological behaviour from the field, a series of numerical simulations are performed. Relative and absolute values are derived for bulk viscosity of the rock units by comparing boundary tortuosity difference measured on the field example and the numerical series. Our analysis shows that during deformation at mid-crustal conditions, paragneisses can be ~ 30 times less viscous than an ultramafic unit, whereas orthogneisses have intermediate viscosity, ~ 3 times greater than the paragneisses. If we assume a strain rate of 10⁻ ¹⁴ s⁻ ¹ the ultramafic, orthogneiss and paragneiss have syn-deformational viscosities of 3 × 10²², 2.3 × 10²¹ and 9.4 × 10²⁰ Pa s, respectively. Our study shows pinch and swell structures are useful as a gauge to assess relative bulk viscosity of rock units based on shape characteristics at the kilometre scale and in non-Newtonian flow regimes, even where heterogeneity occurs within the units at the outcrop scale