Next-generation Digital Earth Michael F. Goodchilda,1, Huadong Guob, Alessandro Annonic, Ling Biand, Kees de Biee, Frederick Campbellf, Max Cragliac, Manfred Ehlersg, John van Genderene, Davina Jacksonh, Anthony J. Lewisi, Martino Pesaresic, Gábor Remetey-Fülöppj, Richard Simpsonk, Andrew Skidmoref, Changlin Wangb, and Peter Woodgatel aDepartment of Geography, University of California, Santa Barbara, CA 93106; bCenter for Earth Observation and Digital Earth, Chinese Academy of Sciences, Beijing 100094, China; cJoint Research Centre of the European Commission, 21027 Ispra, Italy; dDepartment of Geography, University at Buffalo, State University of New York, Buffalo, NY 14261; eFaculty of Geo-Information Science and Earth Observation, University of Twente, 7500 AE, Enschede, The Netherlands; fFred Campbell Consulting, Ottawa, ON, Canada K2H 5G8; gInstitute for Geoinformatics and Remote Sensing, University of Osnabrück, 49076 Osnabrück, Germany; hD_City Network, Newtown 2042, Australia; iDepartment of Geography and Anthropology, Louisiana State University, Baton Rouge, LA 70803; jHungarian Association for Geo-Information, H-1122, Budapest, Hungary; kNextspace, Auckland 1542, New Zealand; and lCooperative Research Center for Spatial Information, Carlton South 3053, Australia Edited by Kenneth Wachter, University of California, Berkeley, CA, and approved May 14, 2012 (received for review March 1, 2012) A speech of then-Vice President Al Gore in 1998 created a vision for a Digital Earth, and played a role in stimulating the development of a first generation of virtual globes, typified by Google Earth, that achieved many but not all the elements of this vision. The technical achievements of Google Earth, and the functionality of this first generation of virtual globes, are reviewed against the Gore vision. Meanwhile, developments in technology continue, the era of “big data” has arrived, the general public is more and more engaged with technology through citizen science and crowd-sourcing, and advances have been made in our scientific understanding of the Earth system. However, although Google Earth stimulated progress in communicating the results of science, there continue to be substantial barriers in the public’s access to science. All these factors prompt a reexamination of the initial vision of Digital Earth, and a discussion of the major elements that should be part of a next generation. scientific communication | visualization igital replicas of complex enti- surface and near-surface of the Earth, and jections entirely by showing the Earth as ties and systems are now rou- could be used to illustrate and even ad- seen from space (technically a perspective D tine in many fields—in the dress a host of problems facing humanity, orthographic projection onto the 2D design and testing stages of from climate change and natural disasters plane of the screen), measured distance by aerospace engineering, in digital re- to warfare, hunger, and poverty (see, for using the length of the shortest path over constructions of ancient cities, or even in example, the 2009 Beijing Declaration the curved surface, and reduced scale to physiology, in which digital cadavers can on Digital Earth; 159.226.224.4/isde6en/ the simple metaphor of raising or lowering replace real ones in the training of medical hykx11.html). The Chinese Academy of the user’s viewpoint. A fly-by, the “magic students. The concept of a Digital Earth, Sciences responded by organizing the first carpet ride” of the Gore speech, the a digital replica of the entire planet, occurs International Symposium on Digital Earth capstone achievement for generations of in Al Gore’s 1992 book Earth in the in Beijing in 1999; the symposium became undergraduate GIS students, could be Balance (1), and was developed further a biennial event, and has been held in created by a child of age 10 in 10 minutes in a speech written for delivery by Gore Canada, the Czech Republic, Japan, the by using nothing more than a home at the opening of the California Sci- United States, China, and Australia. In computer and a downloaded Google ence Center in January 1998 (portal. 2006, the International Society for Digital Earth client. opengeospatial.org/files/?artifact_id= Earth (ISDE) was established, and bi- There will always be a need for flattening 6210). By the turn of the century, support ennial Digital Earth Summits have been the Earth, to see the entire surface at once, for advanced 3D graphics had become convened in New Zealand, Germany, and albeit distorted, or to present information ’ fi standard on personal computers, allowing Bulgaria. In 2008, ISDE sof cial publica- on paper. However, there is no doubt that real-time manipulation of complex ob- tion, the International Journal of Digital virtual globes had enormous advantages jects. Following the speech, the Clinton Earth, was inaugurated. over traditional maps as a means of com- Administration directed NASA to form In this concept of Digital Earth, sharing municating data, information, and knowl- fi fi a Digital Earth of ce, a number of pro- of scienti c information about the planet edge about the surface and near-surface of fi totype projects were begun, and, with the could extend well beyond the scienti c the planet. Here for the first time were 2005 launch of the Google Earth service, community, to people with very limited software environments that could overlay fi — a ne-resolution, digital replica of the technical skills and computing resources layers of information by using geographic planet, or at least of its surface, was within the vision of an information food chain location as a common key, show buildings reach of anyone with a broadband Internet extending all the way from science to and vegetation as complex 3D structures, connection. public policy seemed almost within reach. fi ’ pan and zoom at the click of a mouse, and The effect on the scienti c community Google s own Earth Engine project ex- visualize extracts from petabytes of rapidly was immediate and palpable (2). Here was emplifies this vision by making available a readily accessible technology that could Gore’s “vast quantities of geo-referenced be used to present scientific data and re- information.” Unlike geographic infor- fi Author contributions: M.F.G., H.G., A.A., L.B., K.d.B., F.C., sults (scienti c applications of Google mation systems (GISs), which have a rep- M.C., M.E., J.v.G., D.J., A.J.L., M.P., G.R.-F., R.S., A.S., C.W., Earth were recently reviewed in ref. 3) in utation for being difficult to learn, and and P.W. wrote the paper. easily digestible, visual form to collabo- force users to confront the intuitively dif- The authors declare no conflict of interest. rators and a general public that perceived ficult spatial concepts of scale and map This article is a PNAS Direct Submission. it as free, fast, and fun. Digital Earth had projections, Digital Earth implementa- 1To whom correspondence should be addressed. E-mail: relevance to any science dealing with the tions such as Google Earth avoided pro- [email protected]. 11088–11094 | PNAS | July 10, 2012 | vol. 109 | no. 28 www.pnas.org/cgi/doi/10.1073/pnas.1202383109 Downloaded by guest on September 28, 2021 PERSPECTIVE accumulating georeferenced information ence. Open-source packages such as dragged to contain the pole itself, or to in fractions of a second. NASA’s World Wind can be extended intersect with 180° longitude. The mathe- It is now 7 years since the launch of with new code, and Google’s Application matics of the spheroid are difficult, and Google Earth, and a similar period has Programming Interface allows Google perhaps shortcuts are being taken, for ex- elapsed since the release of the earliest of Earth functions to be embedded within the ample, by resorting to calculations on the what is now a long list of comparable virtual user’s own application. sphere or on a planar projection when the globes, including NASA’s open-source Virtual globes that are able to capture spheroid becomes less tractable. WorldWind (worldwind.arc.nasa.gov), and display elevation above or below the Problems of dealing with uncertainty Wuhan University’s GeoGlobe, the Chi- surface have obvious applications in may have broader implications. Positions nese Academy of Sciences Digital Earth oceanography, atmospheric science, and on the Earth are the result of measure- Prototype System, Microsoft’s Bing Maps geomorphology. Since its initial launch, ment, and thus have accuracies that are (www.bing.com/maps), Esri’s ArcGIS Google has also enhanced the temporal limited by the measuring device. It is Explorer (www.esri.com/software/arcgis/ dimensions of Google Earth, allowing the a long-established principle of science that explorer/), Unidata’s Integrated Data display of time series and the use of historic measurements should be reported with Viewer (www.unidata.ucar.edu/software/ base maps. Unidata’s Thematic Realtime a numerical precision that matches their idv/), and Digitnext’s VirtualGeo (virtual- Environmental Distributed Data Services accuracy, and the principle provides easy geo.diginext.fr/EN/). It is also more than project (www.unidata.ucar.edu/projects/ access to estimates of inherent uncertainty. a decade since the Gore speech and the THREDDS/) aims to facilitate sharing of However, latitudes and longitudes are vision that did much to motivate these data among Earth scientists using the routinely reported by Google Earth to as efforts, which, in some cases, have ex- Integrated Data Viewer platform, and many as six decimal places of degrees tended well beyond the Gore vision. This includes a full range of 3D and tempo- (corresponding, in the case of latitude, or seems an appropriate time, therefore, to ral support. longitude at the equator, to ∼10 cm) ir- examine what this first generation has Nevertheless, this first generation of respective of the spatial resolution of the achieved, and to envision what might be virtual globes has several limitations, each display.