Semantic mapping using mobile robots

Robotic mapping is the process of automatically constructing an environment representation using mobile robots. We address the problem of semantic mapping, which consists of using mobile robots to create maps that represent not only metric occupancy but also other properties of the environment. Specifically, we develop techniques to build maps that represent activity and navigability of the environment. Our approach to semantic mapping is to combine machine learning techniques with standard mapping algorithms. Supervised learning methods are used to automatically associate properties of space to the desired classification patterns. We present two methods, the first based on hidden Markov models and the second on support vector machines. Both approaches have been tested and experimentally validated in two problem domains: terrain mapping and activity-based mapping.

Direct mesh: A multiresolution approach to terrain visualization

Terrain can be approximated by a triangular mesh consisting millions of 3D points. Multiresolution triangular mesh (MTM) structures are designed to support applications that use terrain data at variable levels of detail (LOD). Typically, an MTM adopts a tree structure where a parent node represents a lower-resolution approximation of its descendants. Given a region of interest (ROI) and a LOD, the process of retrieving the required terrain data from the database is to traverse the MTM tree from the root to reach all the nodes satisfying the ROI and LOD conditions. This process, while being commonly used for multiresolution terrain visualization, is inefficient as either a large number of sequential I/O operations or fetching a large amount of extraneous data is incurred. Various spatial indexes have been proposed in the past to address this problem, however level-by-level tree traversal remains a common practice in order to obtain topological information among the retrieved terrain data. A new MTM data structure called direct mesh is proposed. We demonstrate that with direct mesh the amount of data retrieval can be substantially reduced. Comparing with existing MTM indexing methods, a significant performance improvement has been observed for real-life terrain data.

Dragline automation - a decade of development : shared autonomy for improving mining equipment productivity

Draglines are massive machines commonly used in surface mining to strip overburden, revealing the targeted minerals for extraction. Automating some or all of the phases of operation of these machines offers the potential for significant productivity and maintenance benefits. The mining industry has a history of slow uptake of automation systems due to the challenges contained in the harsh, complex, three-dimensional (3D), dynamically changing mine operating environment. Robotics as a discipline is finally starting to gain acceptance as a technology with the potential to assist mining operations. This article examines the evolution of robotic technologies applied to draglines in the form of machine embedded intelligent systems. Results from this work include a production trial in which 250,000 tons of material was moved autonomously, experiments demonstrating steps towards full autonomy, and teleexcavation experiments in which a dragline in Australia was tasked by an operator in the United States.

Issues in obstacle detection for autonomous mining and construction vehicles

This paper discusses a Dumber of key issues for the development of robust, obstacle detection systems for autonomous mining and construction vehicles. A taxonomy of obstacle detection systems is described; An overview of the state-of- the-art in obstacle detection for outdoor autonomous vehicles is presented with their applicability to the mining and construction environments noted. The issue of so-called fail-safe obstacle detection is then discussed. Finally, we describe the development of an obstacle detection system for a mining vehicle.

Topographic and thermal mapping of volcanic terrain using AVTIS ground-based 94-GHz dual-mode radar/radiometric imager

The All-Weather Volcano Topography Imaging Sensor remote sensing instrument is a custom-built millimeter-wave (MMW) sensor that has been developed as a practical field tool for remote sensing of volcanic terrain at active lava domes. The portable instrument combines active and passive MMW measurements to record topographic and thermal data in almost all weather conditions from ground-based survey points. We describe how the instrument is deployed in the field, the quality of the primary ranging and radiometric measurements, and the postprocessing techniques used to derive the geophysical products of the target terrain, surface temperature, and reflectivity. By comparison of changing topography, we estimate the volume change and the lava extrusion rate. Validation of the MMW radiometry is also presented by quantitative comparison with coincident infrared thermal imagery.

Navigating teacher education: mapping the terrain, surveying the landscape

While there are many small-scale case studies that investigate specific teacher education practices, large scale longitudinal studies designed to provide rich and comprehensive data about the effectiveness of teacher education, are limited (Cochran-Smith & Zeichner, 2005). The Studying the Effectiveness of Teacher Education (SETE) project aims to address this gap by investigating the effectiveness of teacher education programs in preparing teachers for the variety of school settings in which they begin their careers. This three-year study utilises large-scale surveys and case studies, and includes a comprehensive mapping of teacher education programs across Australia. It tracks all 2010/2011 teacher education graduates in Queensland and Victoria to investigate the effectiveness of particular characteristics of their teacher education programs in equipping them with the capacity to meet the learning needs of young people in a diverse range of Australian school settings.

This paper presents the findings from the mapping exercise and the surveys of teachers and principals, and the problematics and possibilities of reading across the data sets. The SETE mapping exercise used publicly available online information to examine the characteristics of initial teacher education programs accredited by the Victorian Institute of Teaching (VIT) and the Queensland College of Teachers (QCT). Preliminary results address, inter alia, the length, content and delivery of programs and critical issues of the development of pedagogical and assessment expertise and preparation to teach in diverse contexts. The paper also presents findings from the first of a series of online surveys completed by teacher education graduates in Queensland and Victoria. Beginning teachers’ responses are mapped against key characteristics of participants' pre-service programs and framed in relation to the key themes of curriculum, pedagogy, assessment, behaviour management, and engagement with school stakeholders and local community.

Vision-based simultaneous localization and mapping in changing outdoor environments

For robots operating in outdoor environments, a number of factors, including weather, time of day, rough terrain, high speeds, and hardware limitations, make performing vision-based simultaneous localization and mapping with current techniques infeasible due to factors such as image blur and/or underexposure, especially on smaller platforms and low-cost hardware. In this paper, we present novel visual place-recognition and odometry techniques that address the challenges posed by low lighting, perceptual change, and low-cost cameras. Our primary contribution is a novel two-step algorithm that combines fast low-resolution whole image matching with a higher-resolution patch-verification step, as well as image saliency methods that simultaneously improve performance and decrease computing time. The algorithms are demonstrated using consumer cameras mounted on a small vehicle in a mixed urban and vegetated environment and a car traversing highway and suburban streets, at different times of day and night and in various weather conditions. The algorithms achieve reliable mapping over the course of a day, both when incrementally incorporating new visual scenes from different times of day into an existing map, and when using a static map comprising visual scenes captured at only one point in time. Using the two-step place-recognition process, we demonstrate for the first time single-image, error-free place recognition at recall rates above 50% across a day-night dataset without prior training or utilization of image sequences. This place-recognition performance enables topologically correct mapping across day-night cycles.

Learned ultra-wideband RADAR sensor model for augmented LIDAR-based traversability mapping in vegetated environments

In vegetated environments, reliable obstacle detection remains a challenge for state-of-the-art methods, which are usually based on geometrical representations of the environment built from LIDAR and/or visual data. In many cases, in practice field robots could safely traverse through vegetation, thereby avoiding costly detours. However, it is often mistakenly interpreted as an obstacle. Classifying vegetation is insufficient since there might be an obstacle hidden behind or within it. Some Ultra-wide band (UWB) radars can penetrate through vegetation to help distinguish actual obstacles from obstacle-free vegetation. However, these sensors provide noisy and low-accuracy data. Therefore, in this work we address the problem of reliable traversability estimation in vegetation by augmenting LIDAR-based traversability mapping with UWB radar data. A sensor model is learned from experimental data using a support vector machine to convert the radar data into occupancy probabilities. These are then fused with LIDAR-based traversability data. The resulting augmented traversability maps capture the fine resolution of LIDAR-based maps but clear safely traversable foliage from being interpreted as obstacle. We validate the approach experimentally using sensors mounted on two different mobile robots, navigating in two different environments.

A hierarchical approach coupled with coarse DEM information for improving the efficiency and accuracy of forest mapping over very rugged terrains

Forest mapping over mountainous terrains is difficult because of high relief Although digital elevation models (DEMs) are often useful to improve mapping accuracy, high quality DEMs are seldom available over large areas, especially in developing countries

Remote Sensing and GIScience in Geomorphological Mapping

The rapid proliferation of remote sensing and geographic information systems (GIS) into geomorphologic mapping has increased the objectivity and efficiency of landform segmentation, measurement, and classification. The near ubiquitous presence of Earth-observing satellites provides an array of perspectives to visualize the biophysical characteristics of landscapes, access inhospitable terrain on a predictable schedule, and study landscape processes when conditions are hazardous. GIS technology has altered the analysis, visualization, and dissemination of landform data due to the shared theoretical concepts that are fundamental to geomorphology and GIScience. The authors review geospatial technology applications in landform mapping (including emerging issues) within glacial, volcanic, landslide, and fluvial research.

Groundwater favorability map using GIS multicriteria data analysis on crystalline terrain, Sao Paulo State, Brazil

This paper presents the groundwater favorability mapping on a fractured terrain in the eastern portion of Sao Paulo State, Brazil. Remote sensing, airborne geophysical data, photogeologic interpretation, geologic and geomorphologic maps and geographic information system (GIS) techniques have been used. The results of cross-tabulation between these maps and well yield data allowed groundwater prospective parameters in a fractured-bedrock aquifer. These prospective parameters are the base for the favorability analysis whose principle is based on the knowledge-driven method. The mutticriteria analysis (weighted linear combination) was carried out to give a groundwater favorabitity map, because the prospective parameters have different weights of importance and different classes of each parameter. The groundwater favorability map was tested by cross-tabulation with new well yield data and spring occurrence. The wells with the highest values of productivity, as well as all the springs occurrence are situated in the excellent and good favorabitity mapped areas. It shows good coherence between the prospective parameters and the well yield and the importance of GIS techniques for definition of target areas for detail study and wells location. (c) 2008 Elsevier B.V. All rights reserved.

Crossing Bowen Street : mapping interventions in the classed subject

Synopsis: Crossing Bowen Street Crossing Bowen Street is an extended novel set in Melbourne, Australia. The protagonist, Meg Flanagan, is accepted to teachers' college. Meg is 24 years old and has worked, and lived out of home, since 17. Having completed her year 12 studies part time while working, she has applied to the Melbourne State College for a Bachelor of Education. Melbourne State College is subsequently 'amalgamated'A into Philip University, the original 19th century sandstone institution which borders MSC. Meg has worked as a medical secretary prior to commencing her studies. An only child, she is the first member of her family to go to university, indeed to finish high school. Tertiary study is exciting for Meg and the novel explores the psychic journey as well as the intellectual one, as Meg experiences challenges to the possibilities for her life and the trajectory along which she once assumed it would flow. The narrative is told through episodic and epistolary forms, with particular periods in Meg's cultural and academic life forming the focus, picking up the integral elements of her journey and examining the psychic context and action. Characters in the undergraduate chapters of the novel are somewhat transient, although very important to Meg's rapidly developing, changing sense of herself. The constant 'trying out' of ways of being and even lifestyles sees Meg losing old 'friendships' and making new, even temporary, ones all the time. This allows the opportunity for Meg to explore her feelings about connecting to others and the nature of her relationships. The Meg reflected back to her by others is of constant interest to her, particularly as she is frequently reminded that others see a very different Meg than she does. The novel commences at the outset of Meg's tertiary career, as she initially articulates the extent of her aspiration, of her sense of the possibility of her own life. Each vignette deals, chronologically, with an aspect of Meg's expanding sense of possibility, socially, emotionally, intellectually. Certain vignettes explore her relations with friends and acquaintances in the course, which in turn provide A In 1988, Federal Labor Minister for Education John Dawkins, devised a plan to end the streaming of Australian tertiary institutions and created what is called the Unified National System. This meant that colleges of advanced education and institutes of technology were either created universities in their own right, or more commonly, merged with an appropriate existing university. This process allows a fascinating insight into the class dimensions of hierarchies and stratifications. The need of universities and their members for status has been profoundly underscored. the background and context for her sexual relationships. That aspect of her developing subjectivity provides a marked contrast, which Meg uses as leverage, when set against her sense of herself as a scholar and her growing notion of entitlement, which allows her to 'choose', where previously she believed she had no choice; the choice is a scholarly career. Within all this, Meg discovers and is deeply empowered by certain political left, and feminist, discourses within the university community. She is equally dismayed and alienated by other feminist practices; her growing engagement with her own agency sees her quickly abandoning feminist subject positions previously dear to her, which served a particular purpose and are now superseded. This notion of feeling betrayed by the promise of a value system (or rather, its practitioners) will recur throughout the action of the novel, as Meg moves into an academic role, first as doctoral student and then as academic, seeking to live her values as practice and to remain true to what her trajectory has taught her. This is crystallised in the novel as the role played by the place she came from, and how that informs, and complicates, who she becomes. The novel seeks to explore the fundamental contradictions in doing so, through Meg's increasing awareness that the academy is not the harmonious, class aware institution she has idealised, but a world driven by status and hierarchies. This realisation must be reconciled in the light of Meg's anxieties about her working-class background. Meg's doctoral training at an elite university underscores her developing sense of what constitutes excellence and the role played by highly influential conservative institutions in maintaining social arrangements. As her academic career unfolds, the holding of a Cambridge PhD allows Meg opportunities to make change as certain privileges are afforded her by virtue of her Cambridge status. Yet it is this very notion that she seeks to challenge. Her growing passion for the State University of Victoria, an institution developed for the education of working-class people, informs her activism within the academy. Why are excellence and equity polarised? Why does the institution matter more than the scholarship? Why is so much practice within universities contrary to the values scholars often claim? These questions are explored through the dynamics of academic working life as student and later as a teacher at a university with an explicit equity agenda. The Start of the End (2003): The action commences on a late Friday after at SUV, when the Department of Communication & Cultural Studies has just been advised of Meg's promotion to Associate Professor. This vignette sees the initial soiree and celebrations and allows Meg to reflect on her experience. As her colleagues and friends are congratulating her, a particular student comes looking for Meg. It is clear that Angela Watson needs course advice particularly from Meg. Their discussion seems a straightforward one on the face of it, but it underscores many things; that Meg has come the full circle in her academic life, and what it is that her journey has really been about. The route to professorial appointment is considered, as is the source of Meg's greatest professional joy and fulfillment; is it scholarship, followed by leadership, in her discipline? It is knowing she has continued to speak and act to change the life chances of all students, wherever possible? Or is it the subtle distilling of both of these, along with the knowledge which emerges from the nexus of teaching and research. That scholarship, new knowledge, surely must be taking us somewhere specific in relation to others? The more we know, the more we can do...to what end? From this reflection, we see the action of the novel unfold. We return to this scene at the end of the novel, as Meg considers the trajectory of her life and its themes in her work. The novel ends as she is faced with the next challenge. Arrival (1989): Acceptance sees Meg as she is attempting to transform her life and create a new one. She has just been advised of her admission to an undergraduate Bachelor of Education program, at the major Melbourne teachers' college. Meg shares her rented home with her high school best friend, Anna, and her fiance, Jason, who appears to be superfluous in her life. Meg is aware he is a partner for who she used to be. We see Meg in her job as a medical secretary and this allows the mapping of Meg's sense of her own world, as she travels between home and work. This first stage of seeking her aspiration- to be an English teacher-evolves. As Meg considers the meaning of what she is about to do and how she knows it is right. This involves a consideration of what work means in our lives and how this is different for jobs according to how they are classed. Her relationship with the life she has known, the person she has been, is changing and this change is represented through her relationship with Jason. Meg's first day at teachers' college demonstrates that she is in a constant, often painful, dialogue with herself. The difficulties she encounters in making sense of the relation between her two 'lives' are thrown into sharp relief. The preparation for college sees Meg interrogating herself about how she can be different. Her initial experiences at the College resonate with her highest expectations of the life that awaits her, of the multiple possibilities currently being authored for her. Her first attendance at classes offers the opportunity to try out some of those possibilities, to test them against those she meets and to map the ways she could discover to 'be'. There is much tension and fear, but also endless excitement and these conflicting emotional states parallel and marble each other. It is on this day that she meets Jennifer Wren, her first real friend at university, who offers so many challenges to Meg. Their friendship involves a constant exhausting shift of subject positions, which Meg is able to look back on with affection in years to come. Going Bowling (1989): within a few weeks of commencing at university, Meg is socializing with some of her new friends, having neatly segmented her home and college lives. Meg has already realised that her friendships fall into separate groups; her friendship with Jennifer and the people Jennifer knows does not find its way into this group. They meet in the city to go bowling and have a meal. While Meg really enjoys these new people, already tensions are developing in relations between the group. Their unofficial leader, Rosemary Marshall, has a tendency to seek control and already resistance is showing. Rosemary particularly does not like Jennifer. Meg is enjoying her flirtation with Pete Danville, whom she has assumed to be gay. His very flattering attention has already developed Meg's confidence and stoked her ego, which has eroded in her stagnating relationship with Jason. Rosie has developed a crush on Pete and seems to take the flirtation with Meg personally. Dynamics in the group become slightly uncomfortable but Meg has grown quickly fond of her new friends, especially flamboyant Marina, another whom Rosemary seems to dislike. The discussions which occur during their evening deepen both the relationships and the tensions between them and draw lines which will determine the outcome of their various friendships. The Ball (1990): In the third year of her degree, much has happened to Meg. She is married to Jason, although she omits him from much of her psychic (and practical) life. Meg and her friends attend the Faculty's annual formal dinner dance. Meg has so far managed to balance the competitiveness which occurs between all of them, both academically and personally. The negotiation of her respective friendships with Jennifer and Marina requires a great deal of diplomacy; the subtext in this is very disturbing to Meg. What exactly is the conflict about? She can't be sure why they don't like each other; it could be Marina's smoking, or Jennifer's confidence to spare, but these things also annoy her, yet she does not fight with either girl as they do with each other. Rose has always insisted that the problem is Jennifer's private school background, but Marina went to a catholic girls' school, so what could the difference be? The ball is initially a happy occasion; the girls dress up and they dance and drink champagne together with the boys. But dynamics operating beneath the surface force their way up. Rosie is ready to force Pete to confront her continuing crush on him; Pete confronts Meg about their ongoing flirtation. Meg gives in and admits to herself for the first time that she does want to be with Pete. He is grown up and exciting and strong. He offers her something she has never had with Jason. Married less than a year, she pushes her husband out of her thoughts. The events of the ball force Meg to confront the differences between all her friends and the discomfort this affords everyone. Rosie's continued need for control over the group is acknowledged. Future Present (1991): Meg lives in Carlton with Pete. This is the busiest year thus far in her academic career and the financial, academic and emotional pressure is showing. This vignette gives us the range of Meg's academic activities and the way her life has fallen since the events at the ball eight months earlier. We see Meg grappling with her own evaluation of the changes in her 'way of being'; trying on different ways of living that she has idealised and finding them just as wanting as the last. Meg faces some key existential questions in this vignette and seeks answers which she finally discovers only she can give. Her relationship with Pete, the values and goals they share (and don't share) are thrown into sharp relief and provide a touchstone for the clearer determination of Meg's aspiration and future. Her relationship with various female friends is also revisited and this offers insight into Meg's constant checking of herself against idealised female templates. There is a crisis of identity and strength which constitutes an important fork in Meg's road. Beyond (1992): Beyond sees Meg determinedly seeking ways she can progress towards her goal, while still constantly checking against herself that postgraduate study (let alone a scholarly life) is available to her. We accompany Meg as she seeks and locates the academic path she wants; this is the backdrop for her further psychic exploration of the women who intimidate yet fascinate her, particularly Heloise Waul, who is a significant influence through Meg's postgraduate career. The sites in which Meg's personal struggles manifest are highlighted in this vignette, particularly in terms of dress and cultural pursuit. The conversations between Meg and Heloise also allow an exploration of the feminist politics of that milieu and the class tensions which operate tacitly within those politics. Bound to the Caucus (1992); Meg has now nearly completed her undergraduate degree and has been active for some time in university life and student politics. Her feminist and socialist education is well advanced. Bound to the Caucus shows us Meg in her student politics world for the first time, where the segue of her activism and academic life have taken her. Meg has found female friends who understand that part of her which struggles with inadequacy, although at this point in the novel this common struggle is not well understood or articulated. It is in this vignette that Meg admits her growing attraction for a Liberal student activist, Stuart Noble; this proscribed liaison raises many questions about values and aspiration, as well as the dominant sexual politics of the time and place. Bound to the Caucus also offers insight into the student activism occurring at universities like Philip in the early 1990s. Divergence (1993): Set in 1993, Meg is now in the early weeks of her honours program, although she has been at work on her thesis on the poet William Blake for some months. Living unhappily in a share household near the University, her relationship with Stuart Noble continues to develop, reaching a crisis point in this period. These events occur in the context of Meg's activist career in the Student Left, particularly as she encounters issues of identity around her class, feminism and difference amongst Left women. While Meg fights these battles passionately in an intense milieu, she considers them emotionally in terms of her changing sense of herself. Meg is increasingly aware that the personal impact of her class is changing for her. Additionally, she explores her relation with a 'boyfriend' of right wing political affiliation; Meg comes to recognise that this relationship is undermining her sense of herself in a way that her relationships with women in the left previously did. Honour Roll (1993): Meg is now undertaking honours and this vignette opens with Meg seeing the honours coordinator, Professor Michaela Moore, who approximates all those apparently middle-class traits to which Meg has such a push-pull relation. We see the return of a chapter of the honours thesis, discussion of the content and the constantly shifting subject positions these experiences offer Meg. This vignette also directly introduces Agnes. Mia and Agnes meet Meg after her supervision and this conversation allows very distinct if tacit class themes to develop. Meg has warmed quickly to Agnes, who is unlike anyone she has known; they have much in common in relation to their work and this binds them. Mia continually presents a viewpoint which irritates Meg, in relation to entitlement: to academic life, to funding, even to questioning how these things are enabled. Honour Roll allows us to see Meg's flourishing theoretical and intellectual life and its role in assisting her emotionally as she re-frames the same conundrums that previously constituted obstacles. The Cusp (1993): Meg's developing friendship with Agnes offers her enormous insights into difference and her developing sense of self and aspiration. While the girls come from diametrical backgrounds, they are united by their passion for their research and scholarly work. Meg is increasingly self-conscious through their discussions in terms of how she has seen herself and allowed herself to dream and seek. Cusp is set at the end of the honours year, prior to the release of results. Meg and Agnes explore their feelings about academia and this leads to discussions of purpose and the role of class within that. This vignette also documents Meg's growing social confidence and those aspects of herself which have become so sure to her, that she no longer considers them at all. Whom (1996): [Not included in this abridged edition]. Set at Cambridge, two thirds into Meg's doctorate, Whom shows Meg in the mental space which will take her back to Melbourne and the State University of Victoria. Having risen to the challenge of doctoral study, she is confronted now by deeper demons, and the need to explore and challenge them in the ambivalent context of Cambridge, which so excites her still, but which has proved empty of the profoundly held higher ideals she expected to see reflected. Set in the midst of Meg's doctoral study, this vignette is dramatically abridged in the submission novel. The importance of Whom lies in its concern with Meg's rapidly shifting sense of herself and her own scholarly subjectivity and the changes to these that the culture of Cambridge has wrought. By the second year of her PhD Meg is crystal clear about her goals and decides to spend the long break at home, rather than travelling, because she wishes to 'touch base' with her future. The action described segues into that in Courting the Enemy. Whom describes Meg's ambivalent and contradictory but passionate feelings about Cambridge. Whom demonstrates Meg's increasing anger at the status and privilege to which her education now automatically admits her, and her need to find some sort of stasis and safety in her emotional life. In this vignette, Meg meets her life partner, Jeremy McCallum (I have intentionally reduced the attention in the novel to Meg's romantic life as she matures into her career). Courting the Enemy (late 1990s): By this time, Meg is a senior lecturer in English at the State University of Victoria, which was established in the nineteenth century as the Worker's College. This vignette starts with Meg's attendance at a University Committee which is considering a transformation in relation to equity in admissions policy. Meg was drawn to SUV because of its transparent and determined commitment to educate the children of working-class people. An attack on the equity admission policy of her university galvanizes Meg and some of her colleagues. The action of the vignette considers the role of the scholar, and of such an institution as SUV, in the light of daily academic life. This vignette is primary in its demonstration of the themes of the novel. In the unabridged version, I took the opportunity to illustrate some of the vast range of administrative, intellectual and even physical demands on a senior scholar in the routine of academic life. In placing Meg in this context, I sought to highlight how a scholar of her values and commitment makes sense of the constantly shifting terrain of her working world and how this continually informs her practice. This vignette is also significant for its retrospective description of Meg's employment at SUV some years earlier. Locus: (1995). This piece of writing stands apart from the rest of the novel. I wished to write in a reflective voice, which might be from Meg's journal, were it not in the (omniscient) third person, in order to consider the headspace and meaning-making which occurs as Meg settles into Cambridge, and the lifestyle her situation allows her. Locus is a deeper engagement with Meg's sense of her identity. It considers the impact on her of the physical journeys she must make to match those of her psyche. These are thoughts too personal for a letter, even to Anna. Meg is exploring her ever shifting self and the growth in her self-belief allows her to explore what is rage; that she was bounded by illusions about her worth. Locus seeks to allow some context for Meg's anger at the role Cambridge plays. I seek to create the space in which Meg's dawning self understanding will lead her to her next, driven, purpose. Letters: throughout the novel letters are used to reveal and inform Meg's relationship with her family. This is an intentional device to distance the birth family in an attempt to blur and muddy an assessment of Meg's class through traditional measures. The letters between Meg and Aunty Jean particularly reveal much of the classed emotional antecedents of Meg's life. There are also letters exchanged with Meg's high school best friend, Anna, who has moved to the country and a very different lifestyle. Meg writes to Anna often, using the acceptance she feels in the friendship and her sense that Anna understands her, to touchstone her own emotional growth. Formal letters from institutions ring changes in settings and mark significant points in the geographical and academic trajectory of the character. All the letters serve to introduce time and event changes consistent with the episodic style of the narrative.