Web Map Service Research Articles

Prototyping the visualization of geographic and sensor data for agriculture

The effectiveness of decision-making processes in the agricultural domain can be improved by integrating current local environmental and agromonitoring with the Geographic Information System (GIS) and wireless sensor networks (WSNs). The presented paper describes conceptual approaches to context-based cartographic visualization methods for agricultural and metrological data acquired by WSN and a portal prototype for integrated visualization.Each sensor used for agricultural applications has a location and can be placed within a broader spatial context. In our study, sensor characteristics (soil temperature and moisture, atmospheric temperature and moisture) were automatically monitored at frequent intervals and these readings were aggregated with geospatial data from both local and remote (Web Map Service) sources. An experimental portal for the integration and visualization of sensor data and geospatial data was designed and prototyped on the basis of an open source interoperable platform. Conceptual approaches were successfully implemented on four experimental small-plot fields planted with different crop species and operated using different soil tillage practices. Experimental fields were situated in the southeast of the Czech Republic. Very Long range Identification Tag (VLIT) technology was used for wireless communication. Sensor observations verified differences in agrometeorological variables for the conventional tillage of soil and the no-tillage variant. Contextual cartographic visualization was successfully deployed for map view, dynamic cartographic symbology, and the dynamic measurement chart.

A Web Map Service implementation for the visualization of multidimensional gridded environmental data

We describe ncWMS, an implementation of the Open Geospatial Consortium's Web Map Service (WMS) specification for multidimensional gridded environmental data. ncWMS can read data in a large number of common scientific data formats – notably the NetCDF format with the Climate and Forecast conventions – then efficiently generate map imagery in thousands of different coordinate reference systems. It is designed to require minimal configuration from the system administrator and, when used in conjunction with a suitable client tool, provides end users with an interactive means for visualizing data without the need to download large files or interpret complex metadata. It is also used as a “bridging” tool providing interoperability between the environmental science community and users of geographic information systems. ncWMS implements a number of extensions to the WMS standard in order to fulfil some common scientific requirements, including the ability to generate plots representing timeseries and vertical sections. We discuss these extensions and their impact upon present and future interoperability. We discuss the conceptual mapping between the WMS data model and the data models used by gridded data formats, highlighting areas in which the mapping is incomplete or ambiguous. We discuss the architecture of the system and particular technical innovations of note, including the algorithms used for fast data reading and image generation. ncWMS has been widely adopted within the environmental data community and we discuss some of the ways in which the software is integrated within data infrastructures and portals.

Sharing data and interpretations of geological maps via standardised metadata and geoportals

The so-called “Informatics-revolution” and related Information Technology (IT) are a chance to increase spreading of geoscientific knowledge and transfer of information represented in geological maps, but, in order to actually take advantage of systems-aided communication, geological information has to be specifically harmonized and standardized. New methodological and technological approaches in the representation and communication of geological maps are enabled by widespread use of Geographic Information Systems (GIS) and web mapping services (e.g. the WMS standard protocol) that i ) allow sharing and spatially discovering maps, and ii ) support interchange of data amongst different systems, experts and communities. Since sharing and retrieving of geological maps through geoportals and spatial data infrastructures spread, problems about semantic heterogeneity and different structures of geological databases (DB) come out. A strategy to meet needs of interoperability consists of integrating geological map DB by standard languages and meta-information, and is carried out by the INSPIRE (Infrastructure for Spatial Information in Europe) European directive that defines two relevant guidelines (the “Data Specification on Geology” and the “Metadata Implementing Rules”) usable to encode and share standardised geological information. An example of application of these standards is the Geoportal of the Torino Unit of the Institute for Geosciences and Earth Resources, where field data, map features and peculiar geological interpretations, extracted from GIS DB of geological maps, are given as single datasets and homogeneously described through specific metadata classes such as the Abstract sub-element and the Lineage sub-element. The two given examples of metadata compilations, referring to the Lis-Trana Fault and to the block stream deposits occurring in the “Torino Ovest” geological map (sheet n.155 of the Geological Map of Italy at 1:50,000 scale), highlight that standardisation is an opportunity i ) to better organize geological information, ii ) to give information about quality of data, and iii ) to specify intended meaning of interpreted features. Since metadata allow bringing out in an explicit format geological concepts and interpretations, reading of maps is improved and geoportals are actually a new method for encoding and sharing geological maps.

Storage and processing of massive remote sensing images using a novel cloud computing platform

In recent years, the rapid development of remote sensing technology has proliferated high-quality images that occupy larger and larger storage spaces. Video has become widespread for environmental observation. Hence, digital data is growing exponentially, and geographic information systems must determine how to manage and process images and video effectively. Researchers cannot limit themselves to desktop PCs due to computational and storage limits. The aim of this article was to propose and implement an architectural design for a novel cloud computing platform based on two Web Coverage Service and Web Map Service interfaces from the Open Geospatial Consortium (OGC), cloud storage from Hadoop Distributed File System (HDFS), and image processing from MapReduce. Results are presented on tablet computers (Asus transformer pad) and websites. Within this framework, we implemented image management as well as simple WebGIS and created an experiment in read/write performance with four kinds of data sets (normal distribution, skew to left, skew to right, and peak in left and right). For write/read performance with HDFS, the proposed system outperformed a local file system for large files (most files ranged from 8 MB to 10 MB), with many concurrent users (simulated threads equal to 40 or 50). An observer on the ground with a touchscreen can identify central points (man-made centroids) of real-time images by tapping the tablet with a finger. A second experiment revealed that the convergence for human intervention was better than convergence for random centroids in two kinds of cloud computing environments.

Method for monitoring and evaluating OWS availability and performance: a case study of OGC WMS

针对互联网上所共享发布的开放地理空间联盟网络服务（OWS）经常会出现不能访问或运行速度缓慢而导致难以利用的问题,为测试和评价这些地理信息服务的可用性和性能,通过研究OWS服务的固有特点,提出了实时监测OWS状态的动态规划模型和基于评价因子、评价权重等参数的评价模型,用以实现对OWS的监测与评价;基于上述模型与因子,设计开发了面向OWS的实时监测和性能评价原型系统,并以OGC网络地图服务（WMS）为例对模型与原型系统进行了实验验证。结果表明：该系统能够对相应的OWS进行实时监测与评价,所提的监测与评价方法与模型可为用户在众多的服务资源中获取其所感兴趣的数据提供参考信息,为地理信息服务使用者查找更优的服务资源提供帮助。

An open source, server-side framework for analytical web mapping and its application to health

In this paper, we detail the design and the implementation of an open source, server-side web mapping framework for the analysis of health data. The framework forms part of a larger project, the goal of which is to provide an analytical web geographical information system (GIS) that enables health experts to analyse spatial aspects of health data. The aim of the framework is to provide a method for the dynamic and flexible spatial visualisation of health data to facilitate data exploration and analysis. Consequently, a dynamic thematic web mapping technique, an extension to the Open Geospatial Consortium (OGC) web map service standard, was developed. The technique combines a data query, processing technique and styling methodology on the fly to generate a thematic map. The resulting thematic map represents a virtual map layer that enables a user to rapidly visually summarise properties of a data-set. A test web interface was developed to assess the efficacy of the web mapping technique. As the dynamic web mapping method builds on existing OGC web mapping standards, it can be readily integrated with the existing lightweight slippy map web clients and virtual globes.

Geospatial metadata retrieval from web services

Nowadays, producers of geospatial data in either raster or vector formats are able to make them available on the World Wide Web by deploying web services that enable users to access and query on those contents even without specific software for geoprocessing. Several providers around the world have deployed instances of WMS (Web Map Service), WFS (Web Feature Service) and WCS (Web Coverage Service), all of them specified by the Open Geospatial Consortium (OGC). In consequence, metadata about the available contents can be retrieved to be compared with similar offline datasets from other sources. This paper presents a brief summary and describes the matching process between the specifications for OGC web services (WMS, WFS and WCS) and the specifications for metadata required by the ISO 19115 - adopted as reference for several national metadata profiles, including the Brazilian one. This process focuses on retrieving metadata about the identification and data quality packages as well as indicates the directions to retrieve metadata related to other packages. Therefore, users are able to assess whether the provided contents fit to their purposes.

Accuracy and privacy aspects in free online reverse geocoding services

Reverse geocoding is defined as the extraction of textual information, such as a name or an address, from geographic coordinates. This technique is common in many geo-application scenarios, e.g., in freely available online-based mapping services. However, if personal data are mapped, confidentiality issues may arise, such as if the data are derived from a crime-incidents database. This research provides an evaluation of seven freely available Web mapping services in regard to reverse geocoding accuracy and privacy aspects. The services' textual accuracy is measured using crime data from Vienna, Austria. The accuracy associated with reverse geocoding is derived for districts with different residential densities to determine whether any error variation is associated with the underlying residential structure. Furthermore, this research investigates the reidentification risk when compromising personal information. Using a free online telephone database and addresses in a crime-incidents dataset, the probable names that are linked to crime victims are identified. The results showed that the accuracy ranges from 0% to 23% depending on the predefined precision level. Comparing seven online reverse geocoding services (TravelGIS, Google Maps, nominatim, ArcGIS, Yahoo, Bing, and Geonames), TravelGIS performs better at the highest precision level, whereas Geonames performs better at a lower precision level. However, the results showed no difference among the districts with different residential densities. As for the reidentification risk, 68% probable victims were identified from the database. This work discusses the specific tasks that users have to complete when retrieving addresses associated with crime-incident locations. The article concludes with an evaluation of the reverse geocoding process and a discussion of the privacy risk associated with it.

An OLS regression model for context-aware tile prefetching in a web map cache

The increasing popularity of web map services has motivated the development of more scalable services in the spatial data infrastructures. Tiled map services have emerged as a scalable alternative to traditional map services. Instead of rendering map images on the fly, a collection of pre-generated image tiles can be served very fast from a server-side cache. However, during the start-up of the service, the cache is initially empty and users experience a poor quality of service. Tile prefetching attempts to improve hit rates by proactively fetching map images without waiting for client requests. While most popular prefetching policies in traditional web caching consider only the previous access history to make predictions, significant improvements could be achieved in web mapping by taking into account the background geographic information. This work proposes a regressive model to predict which areas are likely to be requested in the future based on spatial cross-correlation between an unconstrained catalog of geographic features and a record of past cache requests. Tiles that are anticipated to be most frequently requested can be pre-generated and cached for faster retrieval. Trace-driven simulations with several million cache requests from two different nation-wide public web map services in Spain demonstrate that accurate predictions and performance gains can be obtained with the proposed model.

Performance Testing of Web Map Services tn three Dimensions – X, Y, Scale

Abstract The paper deals with the performance testing of web mapping services. The paper describes map service tests in which it is possible to determine the performance characteristics of a map service, depending on the location and scale of the map. The implementation of the test is tailored to the Web Map Service specifications provided by the Open Geospatial Consortium. The practical experiment consists of testing the map composition acquired from OpenStreetMap data for the area of southwestern Slovakia. These tests permit checking the performance of services in different positions, verifying the configuration of services, the composition of a map, and the visualization of geodata. The task of this paper is to also highlight the fact that it is not sufficient to only interpret a map service performance with conventional indicators. A map service’s performance should be linked to information about the map’s scale and location.

Tianditu: China’s first official online mapping service

Tianditu is China’s first state-sponsored web mapping service. Beijing considers Tianditu part and parcel of its burgeoning endeavor to build a ‘digital China’. The Chinese state created Tianditu to regain some of the ground lost when its monopoly on geographic information was effectively broken. This effort goes hand in hand with Beijing’s intention to compete with and shrink the space occupied by Google mapping services (Google Maps, Google Earth, etc.). Although Tianditu does bestow a certain degree of power on civilian users to interact with and explore geographic data, for political and social reasons the Chinese state tightly controls Tianditu. It is a tool that the regime uses to maintain political power and push ideologies it supports. This type of top-down reinforcement of static geographic knowledge is a far cry from the concept of civilian empowerment as understood in liberal democracies.

Application of Google Maps API with Grails Services for Mapping Highway Construction Sites

Most people agreed that Google Maps set the standard for ease of use when it comes to a free online web mapping services. In addition, different map views are available which user can choose from the options of a terrain view, normal map view, or satellite image view based on their needs. Embedding a Google Maps on a website will not only make it more user-friendly but also enable people to access certain location with more ease. This paper intends to introduce the use of this geoinformatics services from Google along with Grails services in creating a simple interactive map for highway construction sites. A discussion will cover up the use of programming interface provided by Google and Grails (open source web application framework) and also the advantages of embedding the map to the website.

Identification of Optimal Colours for Maps from the Web

Maps which are created on demand by combining geospatial data from different Web Map Services integrate conflicting portrayals and do not satisfy the requirements of effective cartographic communication. A significant improvement is achieved by selecting clearly distinguishable colours which are determined by solving an optimisation problem. Cartographic guidelines and user characteristics (e.g. colour vision impairment) can be incorporated into the optimisation model as constraints which guide the selection of colours.

A neural network based intelligent system for tile prefetching in web map services

Web mapping has become a popular way of distributing interactive digital maps over the internet. Instead of dynamically generating map images on the fly, those can be pre-generated and served from a server-side cache for faster retrieval. However, these caches can grow unmanageably in size when the cartography covers mid to large areas for multiple rendering scales. This forces modest organizations to use partial caches containing just a subset of the total tiles, and makes their services less attractive than other mapping services like Google Maps or Microsoft Bing Maps. This work proposes a neural-network-based intelligent system that predicts which areas are likely to be requested in the future from a catalog of geographic features and a short history of past requests. These priority regions can be used by a tile prefetching policy to achieve an optimal population of the cache. Neural networks are trained and validated using supervised learning with real data-sets from a public nation-wide web map service. Trace-driven simulations demonstrate that accurate long-term predictions, up to 90% in terms of cache-hit ratio, can be obtained with the proposed model by prefetching a low fraction, only the 20% of the total tiles, and with a short training period.

Spatial Modeling of the Black Death in Sweden

AbstractThe purpose of this work is to determine whether spatial modeling can be used to model the spread of the Black Death. The study is limited to models for the propagation of the disease in Sweden in 1350. Geographic data of Swedish water bodies and medieval road networks, historical data on the population in Swedish parishes, including their medieval boundaries, along with historical notes and disease characteristics, were used to build alternative models for spatial distribution. Three different models are presented: one radial, one cost‐based and one combining network analysis and radial propagation. Simulations were made to depict different scenarios on the spread of the disease, as well as the drastic changes in the overall population of Sweden, over a couple of hundred years. For purpose of validation the population decrease estimated in each parish is compared with independent historical documents. Results from model scenarios are visualized in maps of propagation, animated video sequences and a web map service. Our analyses clearly demonstrate the power of spatial analysis and geographic information systems to describe, model and visualize epidemiologic processes in space and time.

OWS4SWAT: Publishing and Sharing SWAT Outputs with OGC standards

The Soil and Water Assessment Tool (SWAT) is a widely used hydrological model that produces several useful outputs (e.g. evapotranspiration, soil moisture, aquifer recharge, river discharge) as text files. Currently, visualizing and publishing SWAT outputs as geospatial data requires a lot of time and repetitive processing steps. Moreover, data used and produced are often not interoperable and restricted to software like ArcGIS or MapWindow. Consequently, integrating SWAT outputs with other datasets and/or models is difficult. To solve these issues, we propose an innovative, scalable and interoperable framework allowing (1) the automatization of post-processing tasks using orchestrated Web Processing Services (WPS) and (2) the publishing of SWAT outputs using interoperable data services (e.g Web Feature Service, Web Map Service). The proposed framework simplifies map/data production and facilitates exchange/integration of hydrological data with other sources.

A distributed open source web-application for spatial multi-criteria evaluation for decision support systems infrastructure

Spatial data availability on internet or intranet rapidly increases. Laymen use this data through applications such as Google Maps, Google Earth and Virtual Earth. Relatively new standards allow interoperable use for publication, sharing and calculation of spatial data. We discuss the opportunities that new spatial and multi-criteria decision analysis web service technologies and standards offer in combination with technology to distribute computing and analysis. We report of the architecture and the first prototype of the open source Distributed Spatial Multi-Criteria Evaluation (D-SMCE) web application. It is extensible by using OSGi technology for modularity and different web-services from spatial domains, such as OGC web mapping, web feature and web processing services, and non-spatial domains, such as Decision Deck. Distributed SMCE is a framework and an application. The theoretical context shows how spatial planning and decision support systems can be understood to evolve, to relate practice of distributed evaluation with standards of D-SMCE.

Open-source mapping and services for Web-based land-cover validation

Monitoring land-cover changes on sites of conservation importance allows environmental problems to be detected, solutions to be developed and the effectiveness of actions to be assessed. However, the remoteness of many sites or a lack of resources means these data are frequently not available. Remote sensing may provide a solution, but large-scale mapping and change detection may not be appropriate, necessitating site-level assessments. These need to be easy to undertake, rapid and cheap. We present an example of a Web-based solution based on free and open-source software and standards (including PostGIS, OpenLayers, Web Map Services, Web Feature Services and GeoServer) to support assessments of land-cover change (and validation of global land-cover maps). Authorised users are provided with means to assess land-cover visually and may optionally provide uncertainty information at various levels: from a general rating of their confidence in an assessment to a quantification of the proportions of land-cover types within a reference area. Versions of this tool have been developed for the TREES-3 initiative (Simonetti et al., 2011). This monitors tropical land-cover change through ground-truthing at latitude/longitude degree confluence points, and for monitoring of change within and around Important Bird Areas (IBAs) by Birdlife International and the Royal Society for the Protection of Birds (RSPB). In this paper we present results from the second of these applications. We also present further details on the potential use of the land-cover change assessment tool on sites of recognised conservation importance, in combination with NDVI and other time series data from the eStation (a system for receiving, processing and disseminating environmental data). We show how the tool can be used to increase the usability of Earth observation data by local stakeholders and experts, and assist in evaluating the impact of protection regimes on land-cover change.

The Global Drought Monitor Portal: The Foundation for a Global Drought Information System

Abstract The international scientific community has long recognized the need for coordinated drought monitoring and response, but many factors have prevented progress in the development of a Global Drought Early Warning System (GDEWS): some of which involve administrative issues (coordinated international action and policy) while others involve scientific, technological, and logistical issues. The creation of the National Integrated Drought Information System (NIDIS) Portal within the United States provided an opportunity to take the first steps toward building the informational foundation for a GDEWS: that is, a Global Drought Information System (GDIS). At a series of workshops sponsored by the World Meteorological Organization (WMO) and Group on Earth Observations (GEO) held in Asheville, North Carolina, in April 2010, it was recommended that a modular approach be taken in the creation of a GDIS and that the NIDIS Portal serve as the foundation for the GDIS structure. Once a NIDIS-based Global Drought Monitor (GDM) Portal (GDMP) established an international drought clearinghouse, the various components of a GDIS (drought monitoring, forecasting, impacts, history, research, and education) and later a GDEWS (drought relief, recovery, and planning) could be constructed atop it. The NIDIS Portal is a web-based information system created to address drought services and early warning in the United States, including drought monitoring, forecasting, impacts, mitigation, research, and education. This portal utilizes Open Geospatial Consortium (OGC) web mapping services (WMS) to incorporate continental drought monitors into the GDMP. As of early 2012, the GDM has incorporated continental drought information for North America (North American Drought Monitor), Europe (European Drought Observatory), and Africa (African Drought Monitor developed by Princeton University); interest has been expressed by groups representing Australia and South America; and coordination with appropriate parties in Asia is also expected. Because of the range of climates across the world and the diverse nature of drought and the sectors it impacts, the construction and functioning of each continental drought monitor needs to be appropriate for the continent in question. The GDMP includes a suite of global drought indicators identified by experts and adopted by the WMO as the necessary measures to examine drought from a meteorological standpoint; these global drought indicators provide a base to assist the global integration and interpretation of the continental drought monitors. The GDMP has been included in recent updates to the GEO Work Plan and has benefited from substantial coordination with WMO on both their Global Framework for Climate Services and the National Drought Policy efforts. The GDMP is recognized as having the potential to be a major contributor to both of these activities.

A Catalogue Service for Internet GIServices Supporting Active Service Evaluation and Real‐Time Quality Monitoring

AbstractInternet‐based Geographical Information Services (GIServices) have exploded in depth and variety over the past few years. More and more academic institutions, private companies, and even individuals publish their own geographical information resources in the form of GIServices on the Internet. In today's resource‐rich environment, fast and accurate service discovery is a significant problem for industry and academia, as well as regular users. To solve this problem, researchers introduced Service‐Oriented Architecture (SOA) to the domain of GIServices. Being the core of SOA, a registry catalogue implements message exchange services. But current catalog service mechanisms lack the capability to search services, to monitor and to provide accurate descriptions for quality of service in an active manner. Therefore, current catalogue services are not able to overcome problems such as limited registered resources, inaccurate registration information and the uncertainty of service status in various geospatial applications. A catalogue framework for GIServices is proposed that effectively integrates the Quality of GIServices (QoGIService) theory, as well as service crawling/search and dynamic monitoring techniques. A prototype application focused on Web Map Services (WMS) was established that mitigated the abovementioned problems through active service evaluation and real‐time quality monitoring mechanisms.