Minimum spanning trees for valley and ridge characterization in digital elevation maps

Texture synthesis employs neighbourhood matching to generate appropriate new content. Terrain synthesis has the added constraint that new content must be geographically plausible. The profile recognition and polygon breaking algorithm (PPA) [Chang et al. 1998] provides a robust mechanism for characterizing terrain as systems of valley and ridge lines in digital elevation maps. We exploit this to create a terrain characterization metric that is robust, efficient to compute and is sensitive to terrain properties.

Terrain regions are characterized as a minimum spanning tree derived from a graph created from the sample points of the elevation map which are encoded as weights in the edges of the graph. This formulation allows us to provide a single consistent feature definition that is sensitive to the pattern of ridges and valleys in the terrain Alternative formulations of these weights provide richer characteristicmeasures and we provide examples of alternate definitions based on curvature and contour measures.

We show that the measure is robust, with a significant portion derived directly from information local to the terrain sample. Global terrain characteristics introduce the issue of over- and underconnected valley/ridge lines when working with sub-regions. This is addressed by providing two graph construction strategies, which respectively provide an upper bound on connectivity as a single spanning tree, and a lower bound as a forest of trees.

Efficient minimum spanning tree algorithms are adapted to the context of terrain data and are shown to provide substantially better performance than previous PPA implementations. In particular, these are able to characterize valley and ridge behaviour at every point even in large elevation maps, providing a measure sensitive to terrain features at all scales.

The resulting graph based formulation provides an efficient and elegant algorithm for characterizing terrain features. The measure can be calculated efficiently, is robust under changes of neighbourhood position, size and resolution and the hybrid measure is sensitive to terrain features both locally and globally.

Towards a cultural historical theory of knowledge mapping: collaboration and activity in the zone of proximal development

This chapter locates knowledge mapping within the theoretical framework of cultural historical activity theory. Cultural historical activity theory provides an analytic tool for understanding how knowledge maps can act as “stimuli-means”: a cultural artefact that can mediate the performance of subjects (Vygotsky, 1978 ). Knowledge maps possess Vygotsky’s double nature: they not only enable students to enact academic practice but also allow refl ection on that practice. They enable students to build an “internal cognitive schematisation of that practice” (Guile, 2005 , p.127). Further, cultural historical activity theory gives the tools to analyse the social context of our use of knowledge maps and thus consider the mediating rules (tacit and explicit) and division of labour that mediate our use of knowledge maps. Knowledge maps can be viewed as acting within Brandom’s ( 2000 ) space of reasons , which allows learners to use reasons to develop and exchange judgements based on shareable, theoretically articulated concepts and collectively develop the ability to restructure their knowledge and enact these judgements (Guile, 2011 ). In particular multimodal collaborative knowledge maps can act as Vygotsky’s (Vygotsky, 1978 ) zone of proximal development , where teacher and peer-to-peer interaction allow students to solve problems and learn concepts and skills that they would be otherwise unable to tackle.

The importance of digital literacy in the knowledge era

 Digital literacy is an essential skill in the knowledge era. This research found that occupational therapists recognise the importance of digital literacy and are willing to use digital technologies yet barriers exist. Improving digital literacy is a shared concern, to be addressed at the individual, institutional, professional and societal levels.

Renewing assessment practices: literacy teaching and learning in digital environments

Interpretations of “literacy” and approaches to literacy pedagogy and assessment are under renewal as meaning-making and learning are increasingly situated in digitized environments. While the implications of these shifts are in part technological, they are also relational, as students are increasingly positioned as interactive with participatory roles in self-knowledge and increased responsibility for their learning. However, while shifts are occurring in understandings of literacy and approaches to literacy pedagogy, the same cannot be said for the way in which assessments of digital literacies are undertaken. There is a lack of valid, reliable, and practical assessments of new literacies to inform and help students to become better prepared for study, work, and citizenship in digital environments. This article maps five characteristics of effective formative assessment in print-based classrooms with seven affordancesin digital learning and assessment to suggest an analytical framework for examining teacher and student assessment in digital environments. Drawing on data from a research project in which a team of teachers introduced a one-to-one computing program and worked to renew their literacy assessment practices, this article discusses how each of the seven affordances are enacted in the assessment practices in a years five and six primary school classroom. The findings from this research project show that educational technologies have the potential to enable new approaches to teaching, learning, and assessment that better align with the needs of twenty-first century literacy learners. The findings alsosupport approaches to formative assessment that value print and multimodality and engage students in more flexible and differentiated ways. They can enable teachers and students to be re-positioned as designers, knowledge producers, and collaborative learners. The seven affordances provide a framework that holds rich possibilities for teacher learning and planning as prompts to support reflection on formative assessment practices, critique habitual practices, and considernew opportunities.

2014 Australian Association for Research in Education presidential address: educational research and the tree of knowledge in a post human digital age

The 2014, 41st Australian Association for Research in Education (AARE) presidential address is both inspired and guided by the discursive genres of presidential addresses and the role of the president in a member association such as AARE. In the address, typically the president speaks to the members on an issue or issues that are to shape or conclude their term of office, as it is in my case. Like many of the 40 AARE presidents who have gone before me, I will embed some things that are professional, personal and political—not in the interests of advancing my research agenda, but to add ‘‘to the weave and pattern of the association’s history’’ (Reid 2010, p. v). Threads of my research since completing my PhD in 2000 will appear to support the broad argument. Also, I will draw on the outcomes of the 2014 Australian Research Council Discovery round (see Australian Research Council: ARC archives 2016) to encapsulate my key argument that educational research and its (ex)changes are being reshaped: in a post human digital age, the tree of knowledge is mutating. To make my argument, I will review how the thinking and doing of educational research mid-way through the second decade of the twenty-first century is constructed and ask what research endeavours might be created to make the best possible worlds for our member community and the aspirations of the association.