Rob Lemmens

New Generation Sensor Web Enablement

Many sensor networks have been deployed to monitor Earth’s environment, and more will follow in the future. Environmental sensors have improved continuously by becoming smaller, cheaper, and more intelligent. Due to the large number of sensor manufacturers and differing accompanying protocols, integrating diverse sensors into observation systems is not straightforward. A coherent infrastructure is needed to treat sensors in an interoperable, platform-independent and uniform way. The concept of the Sensor Web reflects such a kind of infrastructure for sharing, finding, and accessing sensors and their data across different applications. It hides the heterogeneous sensor hardware and communication protocols from the applications built on top of it. The Sensor Web Enablement initiative of the Open Geospatial Consortium standardizes web service interfaces and data encodings which can be used as building blocks for a Sensor Web. This article illustrates and analyzes the recent developments of the new generation of the Sensor Web Enablement specification framework. Further, we relate the Sensor Web to other emerging concepts such as the Web of Things and point out challenges and resulting future work topics for research on Sensor Web Enablement.

Integrating Semantic and Syntactic Descriptions to Chain Geographic Services

Integrating multiple geographic services from different information communities and spatiolinguistic regions is challenging because of its inherent complexity and heterogeneity. A geographic information systems workflow approach can use semantic and syntactic service descriptions to form service chains that can integrate service discovery, composition, and reuse. Service chaining links remote geographic services to help expert users form complex geoprocessing services and perform timely analysis of geodata. This method facilitates the use of XML-based service description languages to build a geoservice-reuse architecture based on common ontologies and shared service descriptions

Enhancing Geo‐Service Chaining through Deep Service Descriptions

We demonstrate the integrated use of semantic and syntactic service descriptions, called deep service descriptions, for service chaining by combining two prototypes: one that deals with geoservice discovery abstract composition (called ‘GeoMatchMaker’), with one that supports concrete composition and execution of geoservices services (called ‘Integrated Component Designer’). Most other service chaining approaches confine themselves to handling either syntactic or semantic service descriptions. The proprietary formats of these descriptions hamper an effective integration of discovery, composition and execution of multiple services. In essence, service chaining should help a user by

A Data Model for Multi-scale Topographical Data

The lack of fully automated generalisation forces National Mapping Agencies to maintain topographical data sets at different map scales. For consistency between map scales, but also for supporting (future) automated generalisation processes, information on similarities and differences of the separate data sets should be identified and formalised. This includes information on valid data content at the different scales (‘scale state’), but as important is the semantics of multi-scale and generalisation aspects (‘scale event’). As ‘scale state’ and ‘scale event’ are strongly related (‘different sides of the same coin’) it is important to integrate these in a single model. This paper presents a semantically-rich data model for an integrated topographical database, facilitating (semi-)automated generalisation. UML (including OCL) is used to formalise the model. The scope of the model is outlined and the model is presented based on an analysis of several alternatives for modelling multi-scale and generalisation aspects. The model is evaluated by instantiating the model and applying it to test data.

An Interoperable Web Service Architecture to Provide Base Maps Empowered by Automated Generalisation

Producing customized base maps generated by automated generalisation on the web is an important issue in physical planning. In this web context an interoperable architecture is a key requirement. It integrates the necessary data and the functionality to finally perform the generation of the base map. Additionally, interoperability increases the reuse of the architecture for other domains. In this paper we will describe such an architecture. It has two key features: it supports the user profiles to specify the generalisation constraints and the generalisation-enabled WMS, which generates the base map according to the user profiles. The specialized WMS is especially able to access Web Service-based generalisation functionality. For the implementation of the architecture we used Geoserver, 1Spatial’s Clarity and 52° North WPS.

Exploratory querying of SPARQL endpoints in space and time

The linked data Web provides a simple and flexible way of accessing information resources in a self-descriptive format. This offers a realistic chance of perforating existing data silos. However, in order to do so, space, time and other semantic concepts need to function as dimensions for effectively exploring, querying and filtering contents. While triple stores, SPARQL endpoints, and RDF were designed for machine access, large burdens are still placed on a user to simultaneously explore and query the contents of a given endpoint according to these dimensions. First, one has to know the semantic concepts and the type of knowledge contained in an endpoint a-priori in order to query content effectively. Second, one has to be able to write and understand SPARQL and RDF. And third, one has to understand complex data type literals for space and time. In this article, we propose a way to deal with these challenges by interactive visual query construction, i.e., by letting query results feedback into both (space-time) exploration and filtering, and thus enabling exploratory querying. We propose design principles for SPEX (Spatio-temporal content explorer), a tool which helps people unfamiliar with the content of SPARQL endpoints or their syntax to explore the latter in space and time. In a preliminary user study on a repository of historical maps, we found that our feedback principles were effective, however, that successful question answering still requires improvements regarding space-time filtering, vocabulary explanation and the linking of space-time windows with other displays.

The one and many maps: participatory and temporal diversities in OpenStreetMap

OpenStreetMap is an open and collaborative project with thousands of people contributing GPS traces and other data into the making of a global map of places and networks. It is open in the sense that everyone can contribute to the project, and results from the project are free for everyone to reuse. This is contrary to traditional cartography where often a central authority controls the making of the map and its release. Is OpenStreetMap more democratic, and in what sense? Is OpenStreetMap more relevant to the mass, and how can we judge? We define and use several metrics to measure temporal properties of defined areas in OpenStreetMap, and to sample modes of participation in these areas. These metrics are used to graph the datasets representing the current OpenStreetMap so as to reveal unevenness in user participation and data temporality. We use the dataset about Taiwan as a test case to observe participatory and temporal diversities among different areas of Taiwan in OpenStreetMap.

Automated Integration of Geosensors with the Sensor Web to Facilitate Flood Management

It is predicted that severe flooding disasters will occur more and more often in the future, due to expanding land use and an increasing number of extreme meteorological events. For monitoring and managing large-scale floods efficiently, up-to-date information is crucial. Geosensors ranging from water gauges and weather stations to stress monitors attached to dams or bridges are used to gather such information. The various kinds of sensors need to be integrated into an interoperable infrastructure so that the measured data can be easily utilized by different disaster relief organizations. The standardized web service framework of the Sensor Web Enablement initiative (section 2.1) can be used as such an infrastructure, since it has shown its suitability in several projects and applications in past years. However, the integration of newly deployed sensors into the Sensor Web has not been straight-forward. That challenge is addressed by this work. A standards-based architecture enabling the on-the-fly integration of environmental sensors into the Sensor Web is presented. This new approach for an on-the-fly integration of geosensors is generic and can be applied to different types of sensors. We demonstrate and evaluate the developed methods by applying them to the real world use case of the German watershed management organization Wupperverband, where the mobile water gauge, G-WaLe, is used as an example for a new geosensor deployed in an ad-hoc manner to densify the measurement network.

Lost and found, the importance of modelling map content semantically

There is a growing demand within organisations to integrate and reuse geo-information and geo-information processes from within and outside the organisation. Geo-information is increasingly offered through on-line geo-services that dynamically generate geographic output based on a variety of inputs. The process of integrating geo-information and services requires that geo-information and services can be easily found, and that service calls are interoperable. Interoperability means that the services ‘understand’ each other’s messages. A major impediment is formed by the semantic heterogeneity (the differences in meaning) of map content and of the functionality of geo-services. Within this context, this chapter presents solutions for the computer-aided integration of distributed heterogeneous geo-information and geo-services, based on their semantics (the meaning of their content). The chapter provides an introduction to the Semantic Web and explains its application to the discovery and integration of map content and addresses the relevant issues of geographic information representation in this context. At the end it provides an example of a state of the art implementation.

Monitoring Rural Water Points in Tanzania with Mobile Phones: The Evolution of the SEMA App

Development professionals have deployed several mobile phone-based ICT (Information and Communications Technology) platforms in the global South for improving water, health, and education services. In this paper, we focus on a mobile phone-based ICT platform for water services, called Sensors, Empowerment and Accountability in Tanzania (SEMA), developed by our team in the context of an action research project in Tanzania. Water users in villages and district water engineers in local governments may use it to monitor the functionality status of rural water points in the country. We describe the current architecture of the platform’s front-end (the SEMA app) and back-end and elaborate on its deployment in four districts in Tanzania. To conceptualize the evolution of the SEMA app, we use three concepts: transaction-intensiveness, discretion and crowdsourcing. The SEMA app effectively digitized only transaction-intensive tasks in the information flow between water users in villages and district water engineers. Further, it resolved two tensions over time: the tension over what to report (by decreasing the discretion of reporters) and over who should report (by constraining the reporting “crowd”).