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Category: Professional practice
Teaching and Learning Forum 2009 [ Refereed papers ]
Teaching sustainability with overlay mapping and Google Earth

Laura Stocker and Gary Burke
Sustainability Policy Institute
Curtin University of Technology

In this methodological paper we describe an overlay mapping technique using digital technology that can be used in an action-learning process to creatively derive an understanding of a diverse range of sustainability values, and uses, of local places. In an educational setting, place-mapping is an action-learning process that allows students to document and reflect on sense of place and sustainability values, and to learn a technique that will have professional application. Overlay mapping is a visually and analytically powerful technique for finding out, teaching and learning about sustainability. For educators, the initiating questions are: "How do we sustain a place, and how does this place sustain us?" The mapping process helps locate key sustainability 'hotspots' (or 'coldspots') that provide a basis for interpretation and discussion. The overlay mapping technique uses four transparencies, one for each of the layers of sustainability. Key locations are drawn on each transparency placed over a base map. The four transparency layers are then placed onto the base map together to find synergies or interacting "hotspots", and/or missed opportunities for synergies or even negative interactions ('coldspots'). The physical overlay maps can then be transferred to Google Earth, allowing for digital presentation and dissemination. This technique aims to develop and share students' understandings of place(s) and their sustainability traits. Being graphical, it incorporates diverse knowledge, perception, language and communication capacities. It can be applied at many geographical scales, across time frames, and in a wide variety of situations by a diversity of people with or without conventional literacy skills. Information in the digital sustainability maps can be put together to create a composite map and compared or correlated with other GIS data. This paper records the experiences of ten postgraduate students studying sustainability and piloting this method. Strengths, weaknesses and possible improvements are reported here.


Introduction

Wherever we are, we are in a place. An understanding of our relationships as individuals and as a society to that place can lead us into a deepened appreciation of that place, and to a greater commitment to the stewardship and sustainability of that place (Stocker & Netherwood, 2006).

Place is a rich and dynamic dialogue between our selves and the economic, social, cultural and ecological complexities of life (Beatley & Manning, 1997). Places are always political and contested (Hayden, 1995; Stocker & Netherwood, 2006). Almost every place is a cultural landscape with many facets, layers and human expressions (Seddon, 1997) that reflect and maintain power relations (Hayden, 1995) and human relationships with the natural world (Smith, 2001). Indigenous commentators like Marcia Langton (1998) have stated that all of Australia is a cultural landscape and that every part of the country has been touched, walked over, hunted on, and dreamt by its traditional owners and occupants for millennia.

The question we address is 'how might we go about reflecting on the sustainability of complexly storied places resulting from relationships among the land and many generations of Indigenous, locally born and migrant peoples?' Conventional approaches which focus on the collection and analysis of technical data may describe particular events, such as the decline of species, or the amount of resources and energy used to maintain a society, but they do not account for, nor draw on, people's experiences of and relationships to place. We suggest here that place mapping provides a method by which sustainability values can be drawn out/made explicit to participants, documented, interpreted and analysed.

Mapping projects are being undertaken in many schools and communities across the globe (Liebenberg, 2003; Parr et al., undated). One example was described by Mark Baldwin (2004); it involves observing the school surroundings, mapping the cultural and environmental features of the area and developing a concept map. His program called 'Teaming with Nature' is designed to be a unit of study that links into the curriculum in a rigorously educational manner (Baldwin, 2004). One cross-cultural study showed that mapping ability can be developed in children from a very early age (Blades et al., 1998), while other studies show that smaller children focus relate to smaller areas. Blaut (1991) argues that mapping is a natural ability and can be practised by all ages in all cultures. Hence it is applicable to adults and children. Few examples, however, are available of mapping projects carried out by university students (but see Stocker & Burke, 2006). While a single map is not necessarily effective at illustrating a point, mapping can, by using overlays and Google Earth, become more dynamic and interactive. Google Earth provides locally relevant information and user-friendly interactivity that can enhance novice or lay users' experiences (Patterson, 2007). Virtual Globes other than Google Earth may be used but we have chosen Google Earth because of its ready availability and cross-platform capacity (Schultz et al., 2008).

The mapping method we present here provides an inclusive framework that provides scope for deeper understanding of sustainability values, and can be combined with quantitative information from other digital data sets. It can be used across time and it can encompass the perspectives of a highly diverse group. It can variously record: relationships among people; relationships between people and place; and relationships among aspects of a place. The method allows for: sharing and democratising knowledge about, and perceptions of, sustainability; developing a negotiated, collaborative or composite understanding of place(s) and their sustainability traits; working with people across a wide demographic and cultural range; working with people who do not have good written language skills.

In the present paper, we review the evolution of 'overlay mapping' from a land management tool in the rangelands of Western Australia to its adaptation for use as an action-learning method for university students for mapping sense of place and sustainability values. The essence of the overlay mapping method we present here includes students' experiencesof relationship to place as a part of reflexive sustainability assessment. Participants create physical overlay maps which are then transferred to Google Earth, allowing for digital presentation and sharing and combining of results. In an educational setting, our place-mapping method is an action-learning process that allows participants to document and reflect on sense of place and sustainability values, and at the same time to learn a technique that will have professional application.

Overlay mapping: history

The authors first saw the overlay mapping process being used in the semi-arid Gascoyne Murchison rangelands of Western Australia (Gascoyne Murchison Strategy Board, 2004). The overlay mapping process was the creation of Ken Tinley and Hugh Pringle. Pringle and Tinley created the EMU (Ecosystem Management Understanding) project in order to enhance pastoralist land managers' awareness of rangeland landscape ecology and to encourage them to undertake changes in management practices that lead to more sustainable use of natural resources (Pringle et al., 2003).

We recognised that the overlay mapping method as used in the EMU workshops could be adapted and extended using four sustainability layers (ecological, social, cultural and economic) as the themes for the overlays in the mapping process. We saw that the method could be used as a collaborative action-learning exercise to bring together the ideas of a group of people, and incorporate non-conventional, cerebral-left knowledge frameworks/epistemologies.

Sustainability values mapping

The method used in the EMU overlay mapping exercise was adapted and implemented in an educational context for studying sustainability values by Laura Stocker, Gary Burke, Kathryn Netherwood, Jennie Buchanan and Dave Palmer (Stocker & Burke, 2006; Netherwood et al., 2006). This adapted method shares the educational principles of understanding of places and their sustainability values through participatory and relational practices.

The central questions we ask using this adapted method are "How do we sustain a place, and how does the place sustain us?" Our purpose is to provide a different way of seeing and understanding the world and our place in it. From this can flow responsible stewardship of place, or caring for Country.

In the early days of sustainability engagement, (as in the EMU project), ecology and economy were often seen as the two main aspects of sustainable development. Later, the significance of 'social' was noted and incorporated into the models to add to our understanding. Most people have seen Venn diagrams of the three overlapping circles with sustainability in the centre. Many are also familiar with triple bottom line accounting. In this paper, we use a model of sustainability that accounts for culture as well as the conventional aspects of economy, ecology and society, because culture describes the ways of being and meaning that underpin the values that drive our behaviours. The model enables Indigenous as well as non-Indigenous cultural values to be made explicit. As well as significance within each layer, we also use a model that highlights interactivity among these four dimensions. The term 'pillars of sustainability' suggests silos that do not interact. And even the common Venn diagram portrayal of sustainability suggests a very static, abstract world, rather than the reality of dynamism and synergism.

We begin the overlay mapping process by developing an understanding of a place in terms of its layers: cultural, social, economic and ecological. (A student or scholar of sustainability will quickly recognise that these correspond with the four pillars of sustainability.) Thinking of a place in terms of its four 'layers' (rather than pillars), we can develop a visually and analytically powerful method that can be related directly to a map of that place. Naturally, a place is not literally made up of these abstract layers, but they are used here as a means to deconstruct, analyse and reconstruct our understanding of a place. It is precisely our relationships expressed within the layers and the relationships among the layers that are of interest.The synergistic nature of sustainability, and the key to its assessment in this current method, lies in understanding where and how the layers interact to create these synergies.

Alternatively, missed opportunities for synergies ('coldspots') or even a negative interaction between layers may emerge from the overlay mapping process. Western society often functions along reductionist lines: we 'do economics' in an industrial site like Kwinana, we 'do culture' in an art gallery or theatre, we 'do ecology' in a national park or reserve, and we 'do society' at the football club. Although this is a particular and perhaps oversimplified representation, it illustrates the hyper-separation of human activities and the missed opportunities for creating sustainability synergies.

Sustainability practitioners who understand and want to incorporate the transdisciplinary nature of sustainability into the policy formulation process seek to differentiate, then re-integrate the four layers so as to understand the synergies, rather than working in isolation or, creating adversarial approaches between disciplines in the policy formulation process (e.g. economic growth and environmental protection are too frequently polarised).

In the mapping process, for example, we may mark/identify a beach as a place of significance in the ecological layer. When doing the cultural layer we may note that each year a cultural festival occurs on this beach. Both of these aspects of the beach are important to people's positive experiences of the place. However, the festival may actually celebrate the coastal environment in some way: for example, the kite festival at the very windy South Beach in Fremantle, or the Festival of the Wind in the even windier Esperance on the South Coast of WA; or the Sea Dragon festival in Cottesloe highlighting the diverse marine life of the reef there. This synergy between the ecological and cultural layers is an example of an important first step towards sustainability. The synergy could also encompass economic and social dimensions if, say, the Sea Dragon Festival also included marine eco-tours with a focus on educating people about marine conservation. Where layers coincide, it is important to examine whether the layers actually enhance each other (synergise) or whether they just exist in parallel.

Another example is a community garden, which may be a site of economic significance if, as well as the plants, it highlights the research and development of green technologies and practices. It is cultural when it provides participants and users with a sense of meaning, and if it makes a point of honouring Indigenous and other cultures who influence the place in which the garden is maintained. It is part of the social layer if enjoyable and productive meetings of diverse people with a shared interest in gardening meet there. It is ecological if it cultivates respect and understanding of indigenous flora and fauna while producing food and/or aesthetic appeal in an environmentally safe manner.

Educational aims of sustainability values mapping process

The underlying intent of the sustainability values mapping process is to understand those aspects of our places which sustain us and which we, in turn, care for. The specific educational aims are set out below.

Substantive

Technical Process

Google Earth sustainability values mapping: Case study method

Twelve postgraduate students completing a Masters in Sustainability Studies were the participants in this case study. They came from a range of demographic (mid twenties to late sixties), cultural (Thai, Chinese, American, Czech, Australian) and educational/professional backgrounds. They were asked to develop a map of their local place featuring the key sites of sustainability and their values. The emphasis was on what sustains them in their local place, and what they in turn care for and support. The learning objectives were to understand the sustainability sites and values in a local place, and become familiar with a tool for representing these. We asked participants to reflect, finally, on the strengths and weaknesses of the mapping process.

In choosing sites and values, participants were to choose sites and values that were interesting and meaningful to them, and that also reflected the complexities of local sustainability. They were to find the places where the four layers of sustainability interacted to create hotspots and highlight these. The mapping process consisted of several steps.

  1. Participants chose a local government area that they were reasonably familiar with already, or wanted to become familiar with, say in the case of migrants. Areas were urban, suburban or rural.

  2. Participants sourced a map of their chosen area: a street map, tourist map, topographic map, or a satellite map. The enlarged it to A4 or A3 size.

  3. Participants walked or biked around the local area, matching the place to the map and getting better acquainted with it.

  4. Participants used four clear plastic overlays to mark on cultural, social, economic and ecological sites within the local area, respectively. In some cases the sites were individual points, for example an art gallery; in other cases the sites were larger precincts such as the Cappuccino Strip in Fremantle, or the Swan River. They outlined each site using a different colour for each overlay.

    1. The cultural layer relates to shared meaning and how this meaning is expressed. It may include: Indigenous sites and heritage, market places, theatres, art galleries, music clubs, town squares, parks, bushland, cafes, footy ovals.
    2. The social layer relates to how we organise ourselves to provide for our needs. It may include: hospitals, libraries, market places, parks, police station, and cafes.
    3. The economic layer relates to how we generate livelihoods and the resources required to meet our needs and wants. It may include: malls, port, art galleries, farms, tourist sites, market places, and factories.
    4. The ecological layer relates to the features and processes of the natural world. It may include: beaches, sea, parks, bushland, and farms.

  5. Finally, when the plastic overlays were all laid on top of the base map, participants' maps revealed sites of very special significance (hotspots), where many cultural, social, economic and ecological values coincide and synergise; e.g., parks, or a town beach or a market place. So although the methodology initially separates cultural, social, economic and ecological layers for critical reflection, in reality they interact and combine.

  6. In the next stage, participants transferred the information to Google Earth. They did this by creating a folder for each of the four layers: ecological, social, cultural and economic. They marked with a placemark (colour-coded) individual sites of interest. They outlined larger areas (precincts) of interest using polygons (colour-coded). They hyper-linked information relating to sustainability governance and management to the relevant site (eg council chambers, community group HQ). Participants attached photographs, poems or stories to particular sites, too. They added information for each layer from existing relevant databases in Google Earth. They used placemarks to comment on the significance of sites. Google Earth allows users to turn layers on and off, enabling them to reveal the hotspots where synergies among layers may occur, and coldspots where there is little apparent sustainability.

  7. Participants wrote a short exegesis discussing strengths and weaknesses of the mapping process as a means to understanding the sustainability values of a local place. You should reference relevant readings.

Case study findings: Strengths, weaknesses and improvements

Each participant produced the physical map consisting of a base map with plastic overlays of each of the four layers of sustainability; the Google Earth version; and a short exegesis reflecting on the process. Figure 1 shows a screenshot of the map of one participant (Milan Kucera) who was a relatively new arrival to WA living in Kalamunda and wanting to discover more about the sustainability values of the area. The map shows all his colour-coded placemarks and photos but not his commentaries about each place. The map becomes more interpretable as the viewer zooms in, turns layers on and off, and clicks on the placemarks to view the commentaries. The participants identified the following strengths, weaknesses and improvements in the method. We collate and summarise their comments below. Permission was sought and obtained from participants to use their reflections in this paper.

Figure 1

Figure 1: Sustainability map of part of Kalamunda Shire represented in Google Earth by Milan Kucera

Strengths

The exercise helped participants to understand their places better and especially the sustainability values. For most, this was an interesting and enjoyable process. In particular, the method gave participants a way of understanding and analysing the layers of a place and how they can interact and synergise. The layers are seen to be of equal value, therefore rectifying the tendency of analysts to emphasise one layer or another.

Participants found the mapping exercise to be a powerful visual instrument that enabled them to see and assimilate information, as well as being attractive, enjoyable and stimulating. It was found to be a convenient and easy way to mark places, and annotate them with notes, photos, and other documentation. It was a simple technique but the ability to annotate means that complex ideas can be represented.

The mapping process had low barriers to entry: both the physical material and Google Earth are freely available, and easy to learn, use and adapt by those from most backgrounds.

The method emphasised process as much as goal, and emphasised personal exploration and education leading to deliberation and balance. The participants' subjective interpretations and sense of place could be expressed. Google Earth offers powerful databases of background information to support the participant's learning. Subjective and objective understandings of a place could be combined. The Google Earth maps were flexible to use, durable and easy to share and transfer. Collaboration is possible, and desirable, given consistent formatting guidelines. People from different cultural and language backgrounds could be involved and it was not age dependent. The Google Earth maps when combined into a single atlas could help us understand the global and holistic nature of sustainability.

The method has potential to be used as: an urban and land planning tool; the basis for a local sustainability strategy; and a means of assessing sustainability successes and failures in a local area. The levels of accuracy are appropriate to most sustainability assessment needs.

Weaknesses and possible improvements

Maps were static and represented a snapshot in time. It could be desirable to show seasonality and changes over time by using additional layers to represent different times in Google Earth.

A single map depicting the subjective values of a single individual has limited value beyond the learning experience of that person. Participants concluded that it is desirable to combine maps to generate more information and ideas, and a collective understanding of sustainability values.

Scale and granularity affected results. It can be hard to know where to place boundaries of, say, a cultural precinct. Furthermore, mapping at too large a scale, participants can miss subtleties especially when it comes to interpreting hotspots.

A couple of participants commented that the layering part of the method could encourage participants to pigeonhole activities and places into the four layers. However from the authors' point of view, the method specifically requires participants to allocate activities or places to more than one layer if relevant.

One participant commented that he had to suppress the tendency to 'know the results before the mapping started'. This is an important point! If the process is carried out without 'end-gaining' the results can be quite surprising.

Use of Google Earth presented some technical difficulties for some participants; those who had little computer experience found it a bit fiddly and confusing at times; on the other hand participants acknowledged it was a way of enhancing their computer and Internet skills. From a technical perspective, Google Earth requires broadband Internet access which may limit its use in some areas.

With a lot of information, the maps can become congested and difficult to interpret; therefore it is necessary to make use of the capacity of Google Earth to switch layers on and off.

The embedding of photos obscures the underlying map, which can be obstructive if the photos are too large. A function like Panoramio would overcome this problem but would make the kmz files less portable or would require a permanent download site for the photos. This is a possibility for the future.

The digital mapping process made hotspots easy to identify visually but hard to annotate. One participant solved this problem by adding additional folders/layers representing and explaining the hotspots.

Conclusions and future directions

The sustainability values mapping process, as derived from the EMU overlay mapping process, is a method that compiles and represents the sustainability values of a place. In this case study, the method enabled participants to reflect on their local area as a cultural landscape with many facets and complex relationships among social, ecological, economic and cultural layers (Hayden, 1995; Seddon, 1997; Smith, 2001). In this way, the mapping allowed participants to explore in a novel, meaningful way the sustainability issues and stories in their local areas.

The overlay mapping can be highly successful without using Google Earth but this program does allow easy reproduction, manipulation and transferability of results, as well as opportunity to add data from a huge range of databases.

The project we describe in this paper was the first time researchers have tried to transfer the overlay mapping process into Google Earth for the purpose of interpretive sustainability mapping. Overall the method was successful and enjoyable for the participants as an action-learning process. We found that Google Earth helped make the mapping process more dynamic and flexible. It enabled the use of locally relevant information and user-friendly interactivity that enhanced participants' experiences of mapping whether they were novices or experienced computer users (Patterson, 2007).

Participants were also able to suggest improvements for next year, mostly of a technical/design nature, as documented above. The idea of a composite map showing intersubjective understandings of a place as well as objective data is very appealing from a participant as well as a professional perspective.

Further work can be done with digital format. The completed digital maps can be formatted into a GIS (GeographicInformation Systems) program and correlated and analysed with data collected elsewhere and by different means (e.g. ABS census). The availability of personal GPS devices, combined with the ease with which electronic maps can now be created (e.g. from a traditional Indigenous painting of Country), and graphics based, non-literary software programs such as Cybertracker for PDA/GPS (Personal Digital Assistant/Global Positioning System) devices, means there is greater potential for effective incorporation of information and perspectives from many citizens who are usually marginalised by information gathering processes (Liebenberg, 2003).

Until recently, GIS has been much less user-friendly for collaborative, participatory grass-roots work. However there are pilot projects being undertaken in local governments in Europe that involve using internet and GIS to enhance public participation (Parr et al., undated) and in Vermont, USA, there has been a collaboration between the University of Vermont, Shelburne Farms and other partners in mapping the physical, cultural and ecological landscapes and their key attributes of Vermont towns specifically as a place-based community educational process (PLACE, undated). The advantages of the GIS approach is that it is very information rich but the disadvantage is that, without the capacity for easy public input via the internet (because of lack of access, for instance) it does not necessarily capture the relational values that were can be so important in education.

Acknowledgments

We would like to thank: Brenton Burger, Sompak Cheamjumras, Cara Clifton, Ian Jackson, Milan Kucera, Dinny Laurence, Shoufu Lin, James Nerva, Chiara Pacifici, Andrew Went and JiuChang Wei, Rob Weymouth for their thoughtful reflections on this mapping exercise and for being such enthusiastic participants.

References

Baldwin, M. (2004). Teaming with Nature. Green Teacher, 74(October), 27-30.

Beatley, T. & Manning, K. (1997). The ecology of place: Planning for environment, economy, and community. Washington: Island Press.

Blaut J.M. (1991). Natural mapping. Transactions of the Institute of British Geographers New Series, 16(1), 65-74.

Blades, M., J.M. Blaut, Z. Darvizeh, S. Elguea, S. Sowden, D. Soni, C. Spencer, D. Stea, R. Surajpaul, D. Uttal (1998). A cross-cultural study of young children's mapping abilities. Transactions of the Institute of British Geographers New Series, 23(2), 269-277.

Braddick, L. (2005). Ecological Management Unit Project: Participant evaluation. Kalgoorlie, Western Australia: The Rangeland Natural Resource Management Co-ordinating Group.

Burke, G. (2005). Overview of the Ecosystem Management Understanding Framework (EMU): Principles and Practice for Ecologically Sustainable Pastoral Management, Video produced for GMS. Fremantle: Production Function.

Gascoyne Murchison Strategy Board (2004). Gascoyne Murchison Strategy Annual Report 2003-2004. Western Australia: Gascoyne Development Commission. http://www.gms.wa.gov.au/main%20pages/programs.html#vla

Hayden, D. (1995). The power of place: Urban landscapes as public history. Cambridge: MIT Press.

Langton, M. (1998). Burning questions: Emerging environmental issues for indigenous peoples in northern Australia. Darwin: Centre for Indigenous Natural and Cultural Resource Management, Northern Territory University.

Liebenberg, L. (2003). A new environmental monitoring methodology. http://www.cybertracker.co.za/index_environment.html

Netherwood, K., Buchanan, J., Palmer, D., Stocker, L. & Down, B. (2007). Valuing diversity in children's voices - case study of the Western Australian Cluster. In T. Lovat & R. Toomey (eds), Values education and quality teaching: The double helix effect. Terrigal: David Barlow,

Netherwood, K., Buchanan, J., Stocker, L. & Palmer, D. (2006). Values education for relational sustainability: A case study of Lance Holt School and friends. Chapter 27 in S. Wooltorton & D. Marinova (eds), Sharing wisdom for our future: Environmental education in action. Sydney: Australian Association for Environmental Education.

Parr, C., Jones, T. & Songer, N.B. (undated). CyberTracker in BioKIDS: Customization of a PDA-based scientific data collection application for inquiry learning. http://www.cybertracker.co.za/

Patterson, T. (2007). Google Earth as a (not just) geography education tool. Journal of Geography 106, 145-152.

PLACE (undated). What is GIS? PLACE: Place-based Landscape Analysis and Community Education: University of Vermont. [verified 13 Jan 2008] http://www.uvm.edu/place/analyze/gis.php

Pringle, H., K. Tinley, T. Brandis, A. Hopkins, M. Lewis M. & L. Taylor (2003). The Gascoyne-Murchison Strategy: A people centred approach to conservation in arid Western Australia. African Journal of Range & Forage Science, 20(2), 80-88.

Schultz, R., Kerski, J. & Patterson, T. (2008). The use of virtual globes as a spatial teaching tool with suggestions for metadata standards. Journal of Geography, 107, 27-34.

Seddon, G. (1997). The genius loci and the Australian landscape. Chapter 12 in Landprints: Reflections on place and landscape. Cambridge: Cambridge University Press.

Stocker, L.J. (1995). Community science and community scientists: Their role in conservation. In D.A. Saunders, J. Craig & E. Mattiske (Eds.), Nature conservation 4: The role of networks. Australia: Surrey Beatty & Sons Ltd.

Stocker, L.J. & Netherwood, K. (2006). Children caring for the coast: A values education project on sustainability in place. In S. Paulin (Ed.), Community voices: Creating sustainable spaces. Perth: UWA Press.

Stocker, L. & Burke, G. (2006). Overlay mapping - A methodology for place-based sustainability education. Chapter 25 in S. Wooltorton & D. Marinova (eds), Sharing wisdom for our future: Environmental education in action. Sydney: Australian Association for Environmental Education.

Authors: Laura Stocker and Gary Burke
Sustainability Policy Institute, Curtin University of Technology
Email: L.Stocker@curtin.edu.au, Gary.Burke@postgrad.curtin.edu.au

Please cite as: Stocker, L. & Burke, G. (2009). Teaching sustainability with overlay mapping and Google Earth. In Teaching and learning for global graduates. Proceedings of the 18th Annual Teaching Learning Forum, 29-30 January 2009. Perth: Curtin University of Technology. http://otl.curtin.edu.au/tlf/tlf2009/refereed/stocker.html

Copyright 2009 Laura Stocker and Gary Burke. The authors assign to the TL Forum and not for profit educational institutions a non-exclusive licence to reproduce this article for personal use or for institutional teaching and learning purposes, in any format (including website mirrors), provided that the article is used and cited in accordance with the usual academic conventions.


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