Digital Earth: a new challenge and new vision

ABSTRACT

Digital Earth has seen great progress during the last 19 years. When it entered into the era of big data, Digital Earth developed into a new stage, namely one characterized by ‘Big Earth Data’, confronting new challenges and opportunities. In this paper we give an overview of the development of Digital Earth by summarizing research achievements and marking the milestones of Digital Earth’s development. Then, the opportunities and challenges that Big Earth Data faces are discussed. As a data-intensive scientific research approach, Big Earth Data provides a new vision and methodology to Earth sciences, and the paper identifies the advantages of Big Earth Data to scientific research, especially in knowledge discovery and global change research. We believe that Big Earth Data will advance and promote the development of Digital Earth.     

Big Earth data: disruptive changes in Earth observation data management and analysis?

ABSTRACT

Turning Earth observation (EO) data consistently and systematically into valuable global information layers is an ongoing challenge for the EO community. Recently, the term ‘big Earth data’ emerged to describe massive EO datasets that confronts analysts and their traditional workflows with a range of challenges. We argue that the altered circumstances must be actively intercepted by an evolution of EO to revolutionise their application in various domains. The disruptive element is that analysts and end-users increasingly rely on Web-based workflows. In this contribution we study selected systems and portals, put them in the context of challenges and opportunities and highlight selected shortcomings and possible future developments that we consider relevant for the imminent uptake of big Earth data.     

The Generalised Settlement Area: mapping the Earth surface in the vicinity of built-up areas

ABSTRACT

Geo-information on settlements from Earth Observation offers a base for objective and scalable monitoring of the evolution of cities and settlements, including their location, extent and other attributes. In this work, we deploy the best available global knowledge on the presence of human settlements and built-up structures derived from Earth Observation to advance the understanding of the human presence on Earth. We start from a concept of Generalised Settlement Area to identify the Earth surface within which any built-up structure is present. We further characterise the resulted map by using an agreement map among the state of the art of remote sensing products mapping built-up areas or other strictly related semantic abstractions as urban areas or artificial surfaces. The agreement map is formed by a grid of 1?km², where each cell is classified according to the number of EO-derived products reporting any positive occurrence of the abstractions related to the presence of built-up structures. The paper describes the characteristics of the Generalised Settlement Area, the differences in the agreement map across geographic regions of the world, and outlines the implications for potential users of the EO-derived products used in this study.     

A digital earth platform for sustainability

ABSTRACT

Based on the experience of the International Society for Digital Earth (ISDE), this paper describes some challenges foreseen in order to develop a Digital Earth platform that can support the implementation of the Sustainable Development Goals. The use of ready-to-use derived geospatial information is essential. Future Earth’s methodology of ‘co-design’ aims to bring together natural, social scientists and decision makers to plan and carry out research for sustainability. Sustainability implies transdisciplinary research, but in order for scientists of different disciplines to work together, they will need to be able to share, access and use common data. This is by far not simple! While the good will to share data might exist, the associated technological, ethical and privacy issues are difficult to solve. An adequate e-infrastructure will be required. ISDE could consider to use the SDGs is the basis to develop the desired Digital Earth platform. This paper, by no means, covers everything for a Digital Earth platform, it aims to trigger research discussions and to have a good view about a starting point.     

Error analysis of exterior orientation elements on geolocation for a Moon-based Earth observation optical sensor

ABSTRACT

The Moon is a potential new platform for Earth observation. The advantages of its large-scale observational scope, long temporal duration, and multi-layer detecting of the Earth will undoubtedly advance our understanding of the Earth system. To carry out the observations from a Moon-based optical sensor, the geolocation error caused by exterior orientation elements need to be investigated. This paper analyses the error effects of exterior orientation elements on geolocation for an optical sensor. To estimate the error, we present a geometric image model and utilise some parameters to measure the image offsets. Through a large number of numerical simulations, the results demonstrate that the image offsets are not obvious influenced by the distance and observation angle at mid-high latitude of the Moon and have linear correlation with the increasing errors of the exterior orientation elements. Further, the relationship between the spatial resolution and errors of exterior orientation elements are revealed. Finally, the error characteristics for Moon-based Earth observation are discussed. It is expected that the conclusion drawn in this paper could support the study of a Moon-based Earth observation optical sensor.     

The angular characteristics of Moon-based Earth observations

ABSTRACT

The Moon, Earth’s only natural satellite, is a potential new platform for Earth observation. Moreover, with the wide applicability of the angular information from remote sensing data, it has been attracting increasingly more attention. Accordingly, this study focuses on the angular characteristics of Moon-based Earth observations. Using ephemeris DE430 and Earth orientation parameters, the position and attitude of the Sun, Earth, and Moon were obtained and their coordinates normalized to a single framework using coordinate transformations between the related reference systems. Then, an angular geometric model of Moon-based Earth observations was constructed, and the corresponding angular algorithms were presented. The results revealed the angular range and distribution characteristics of Moon-based Earth observations. For every point on the surface of the Earth, the view and solar zenith angles all vary widely, which decreases with increasing latitude. The view and solar zenith angles all vary widely with the largest range of values in the equatorial and polar regions and a smaller range of values in mid-latitudes. Furthermore, the range of solar angles of Moon-based Earth observations is the same as that of all-time solar angles, indicating the potential for monitoring and understanding large-scale geoscientific phenomena using Moon-based Earth observations.     

Overview and preliminary idea for building Digital Earth with Grid computing technology

Abstract

Digital Earth is an important field of information technology and a research frontier of geosciences in the 21st century. So far, the Grid computing technique is one of the best solutions for Digital Earth infrastructure. Digital Earth can only be realised through the interaction of people, heterogeneous computing resources, information systems, and instruments, all of which are geographically and organisationally dispersed. Earth observation (EO) includes information acquisition, processing and applications. Information acquisition provides a vast amount of spatial data for building the fabric resource infrastructure. Information processing means that spatial information processing middleware is used with large amounts of secure Grid computing resources for real-time processing of all kinds of spatial data. We are currently working on the development of core-middleware for EO data processing and applications for the Digital Earth Prototype System, which is available in the Institute of Remote Sensing Applications (IRSA), Chinese Academy of Sciences (CAS) The further results will be available soon.     

Wāhi,a discrete global grid gazetteer built using linked open data

ABSTRACT

Discrete global grid systems have become an important component of Digital Earth systems. However, previously there has not existed an easy way to map between named places (toponyms) and the cells of a discrete global grid system. The lack of such a tool has limited the opportunities to synthesize social place-based data with the more standard Earth and environmental science data currently being analyzed in Digital Earth applications. This paper introduces Wāhi, the first gazetteer to map entities from the GeoNames database to multiple discrete global grid systems. A gazetteer service is presented that exposes the grid system and the associated gazetteer data as Linked Data. A set of use cases for the discrete global grid gazetteer is discussed.     

Exploring the reasons for the seasons using Google Earth, 3D models,and plots

ABSTRACT

Public understanding of climate and climate change is of broad societal importance. However, misconceptions regarding reasons for the seasons abound amongst students, teachers, and the public, many of whom believe that seasonality is caused by large variations in Earth’s distance from the Sun. Misconceptions may be reinforced by textbook illustrations that exaggerate eccentricity or show an inclined view of Earth’s near-circular orbit. Textbook explanations that omit multiple factors influencing seasons, that do not mesh with students’ experiences, or that are erroneous, hinder scientifically valid reasoning. Studies show that many teachers share their students’ misconceptions, and even when they understand basic concepts, teachers may fail to appreciate the range of factors contributing to seasonal change, or their relative importance. We have therefore developed a learning resource using Google Earth, a virtual globe with other useful, weather- and climate-related visualizations. A classroom test of 27 undergraduates in a public research university showed that 15 improved their test scores after the Google Earth-based laboratory class, whereas 5 disimproved. Mean correct answers rose from 4.7/10 to 6/10, giving a paired t-test value of 0.21. After using Google Earth, students are helped to segue to a heliocentric view.     

Review of the development of digital earth research during 1998–2015 based on a bibliometric analysis

ABSTRACT

Since Al Gore created the vision for Digital Earth in 1998, a wide range of research in this field has been published in journals. However, little attention has been paid to bibliometric analysis of the literature on Digital Earth. This study uses a bibliometric analysis methodology to study the publications related to Digital Earth in the Science Citation Index database and Social Science Citation Index database (via the Web of Science online services) during the period from 1998 to 2015. In this paper, we developed a novel keyword set for ‘Digital Earth’. Using this keyword set, 11,061 scientific articles from 23 subject categories were retrieved. Based on the searched articles, we analyzed the spatiotemporal characteristics of publication outputs, the subject categories and the major journals. Then, authors’ performance, affiliations, cooperation, and funding institutes were evaluated. Finally, keywords were examined. Through keyword clustering, research hotspots in the field of Digital Earth were detected. We assume that the results coincide well with the position of Digital Earth research in the context of big data.     

Optimal orientations of discrete global grids and the Poles of Inaccessibility

ABSTRACT

Spatial analyses involving binning often require that every bin have the same area, but this is impossible using a rectangular grid laid over the Earth or over any projection of the Earth. Discrete global grids use hexagons, triangles, and diamonds to overcome this issue, overlaying the Earth with equally-sized bins. Such discrete global grids are formed by tiling the faces of a polyhedron. Previously, the orientations of these polyhedra have been chosen to satisfy only simple criteria such as equatorial symmetry or minimizing the number of vertices intersecting landmasses. However, projection distortion and singularities in discrete global grids mean that such simple orientations may not be sufficient for all use cases. Here, I present an algorithm for finding suitable orientations; this involves solving a nonconvex optimization problem. As a side-effect of this study I show that Fuller's Dymaxion map corresponds closely to one of the optimal orientations I find. I also give new high-accuracy calculations of the Poles of Inaccessibility, which show that Point Nemo, the Oceanic Pole of Inaccessibility, is 15?km farther from land than previously recognized.     

Evolution and implementation of the Digital Earth vision,technology and society

Abstract

Digital Earth's framework can be traced to evolutionary threads with historic foundations that fostered the fertile conceptual and technological incubation. These threads incorporate writings, such as those of the visionary engineering-genius, Buckminster Fuller, in conjunction with an array of space age developments in computers, internet and communications, satellites, and education. In 1998, when Vice President Al Gore articulated the Digital Earth Vision, he portrayed the vision based upon myriad technology factors for the intellectual foundation and sparked a worldwide phenomenon that fortuitously included the Chinese leadership's recognition and acceptance. The Beijing Declaration is recognised for its role promulgating the International Digital Earth Symposium series to promote better understanding of the impacts of Digital Earth technology and applications on behalf of all humankind. Combinations of industrial, academic, and government organisations have advanced the technological components necessary for implementing the Digital Earth Vision at a prodigious rate. Commercial leaders, such as Google, have accelerated the influence of large segments of society towards components of the Digital Earth Vision. However, challenges still remain regarding requisite collaboration on international standards for metadata, interoperability, and data formats for space and time that will affect Digital Earth implementation scenarios. Functional requirements for the model Digital Earth geobrowser remain to be fully articulated. The current paper presents an overview of the historical components, the key players on the international scene, the catalytic technological advances, and the societal response to the growth of the Digital Earth community.     

Towards integrated essential variables for sustainability

ABSTRACT

Measuring the achievement of a sustainable development requires the integration of various data sets and disciplines describing bio-physical and socio-economic conditions. These data allow characterizing any location on Earth, assessing the status of the environment at various scales (e.g. national, regional, global), understanding interactions between different systems (e.g. atmosphere, hydrosphere, biosphere, geosphere), and modeling future changes. The Group on Earth Observations (GEO) was established in 2005 in response to the need for coordinated, comprehensive, and sustained observations related to the state of the Earth. GEO’s global engagement priorities include supporting the UN 2030 Agenda for Sustainable Development, the Paris Agreement on Climate, and the Sendai Framework for Disaster Risk Reduction. A proposition is made for generalizing and integrating the concept of EVs across the Societal Benefit Areas of GEO and across the border between Socio-Economic and Earth systems EVs. The contributions of the European Union projects ConnectinGEO and GEOEssential in the evaluation of existing EV classes are introduced. Finally, the main aim of the 10 papers of the special issue is shortly presented and mapped according to the proposed typology of SBA-related EV classes.     

Arithmetic and Fourier transform for the PYXIS multi-resolution digital Earth model

Abstract

This paper investigates a multi-resolution digital Earth model called PYXIS, which was developed by PYXIS Innovation Inc. The PYXIS hexagonal grids employ an efficient hierarchical labeling scheme for addressing pixels. We provide a recursive definition of the PYXIS grids, a systematic approach to the labeling, an algorithm to add PYXIS labels, and a discussion of the discrete Fourier transform on PYXIS grids.     

Digital Earth in support of global change research

Abstract

The Digital Earth concept as originally proposed by former US Vice president Al Gore is now well established and widely adopted internationally. Similarly, many researchers world-wide are studying the causes, effects and impacts of Global Change. The authors commence by describing a five-step approach to the development of Digital Earth technologies. This is followed by a detailed account of Digital Earth research and developments in China. The authors then present the research results of Global Change studies carried out in China, based on the Digital Earth approach. These research results are based on a classification of global change regions. This covers the following global change situations:

Forest and grassland fires in Northern China, temperate region desertification and dust storms, underground coal fires, deforestation and carbon sequestration, protection and utilisation of wetlands, Avian Influenza and the spread of diseases, Tibet Plateau uplift and sub-tropical monsoon climate region, and sea-level rise. The research results show that the environment does not behave in a way easily understood by the traditional disciplinary approach. Although man is clearly a contributing factor to certain Global Change aspects, such as underground coal fires, desertification, land use changes etc., many of the aspects of Global Change are naturally occurring phenomena which have been changing over centuries, and will continue to do so, no matter what actions we undertake to reverse these processes. Hence, in their conclusions, the authors propose that the communities involved in Digital Earth modelling and in Global Change research co-operate closer to overcome the limitations inherent in the current ‘conventional’ scientific approach, where scientists have very much stayed within their respective scientific boundaries. Such an integrated approach will enable us to build the next level of scientific infrastructure required to understand and predict naturally occurring environmental changes, as well as that of coupled human–environmental systems.     

The framework of a geospatial semantic web-based spatial decision support system for Digital Earth

Abstract

While significant progress has been made to implement the Digital Earth vision, current implementation only makes it easy to integrate and share spatial data from distributed sources and has limited capabilities to integrate data and models for simulating social and physical processes. To achieve effectiveness of decision-making using Digital Earth for understanding the Earth and its systems, new infrastructures that provide capabilities of computational simulation are needed. This paper proposed a framework of geospatial semantic web-based interoperable spatial decision support systems (SDSSs) to expand capabilities of the currently implemented infrastructure of Digital Earth. Main technologies applied in the framework such as heterogeneous ontology integration, ontology-based catalog service, and web service composition were introduced. We proposed a partition-refinement algorithm for ontology matching and integration, and an algorithm for web service discovery and composition. The proposed interoperable SDSS enables decision-makers to reuse and integrate geospatial data and geoprocessing resources from heterogeneous sources across the Internet. Based on the proposed framework, a prototype to assist in protective boundary delimitation for Lunan Stone Forest conservation was implemented to demonstrate how ontology-based web services and the services-oriented architecture can contribute to the development of interoperable SDSSs in support of Digital Earth for decision-making.     

A VLBI Delay Model for Radio Sources at a Finite Distance

A relativistic delay model for Earth-based very long baseline interferometry (VLBI) observation of sources at finite distances is derived. The model directly provides the VLBI delay in the scale of terrestrial time. The effect of the curved wave front is represented by using a pseudo source vector K = (R ₁ + R ₂)/(R ₁ + R ₂), and the variation of the baseline vector due to the difference of arrival time is taken into account up to the second-order by using Halley’s method. The precision of the new VLBI delay model is 1 ps for all radio sources above 100 km altitude from the Earth’s surface in Earth-based VLBI observation. Simple correction terms (parallax effect) are obtained, which can also adopt the consensus model (e.g. International Earth Rotation and Reference Frames Service conventions) to finite-distance radio source at R > 10 pc with the same precision. The new model may enable estimation of distance to the radio source directly with VLBI delay data.     

The role of GIS in Digital Earth education

Abstract

A growing number of educators worldwide have become convinced that geotechnologies – including geographic information systems (GIS), global positioning systems (GPS), and remote sensing – are key technologies to prepare students to be tomorrow's decision makers. Grappling with local, regional, and global issues of the 21^st century requires people who think spatially and who can use geotechnologies. Some educators teach geotechnologies as a discipline, emphasising skills. Other educators use geotechnologies as a tool to teach content, such as geography, history, environmental studies, Earth Science, biology, mathematics, economics and other disciplines. Issues such as traffic, population growth, urban sprawl, energy, water, crime, human health, biodiversity and sustainable agriculture are growing in complexity, exist at every scale and increasingly affect people's everyday lives. Each of these issues has a spatial component. Drivers for geotechnology education include educational content standards, constructivism, the school-to-career movement, active learning, citizenship education, authentic practice and assessment, interdisciplinary education, community connections and a sustained, increasing demand for GIS professionals. Digital Earth is an ideal framework for contextualising domains of inquiry. The Digital Earth community can have a significant impact on the growth of geotechnologies in education, and conversely, the growth of geotechnologies in education and society can foster the forward movement of Earth systems concepts.     

Production of Photomaps

Abstract

This paper comprises a short review of the methods followed and the results which have been obtained in Delft at the Topographic Service of the Netherlands and at the International Training Centre for Aerial Survey and Earth Sciences. After an introduction describing the principle of orthophotograph production, applications in the Netherlands, South Korea, Saudi Arabia and Mauritius are discussed.