World Congress on Software Engineering
Building Spatial information Systems Based on Geospatial Web Services
Zongyao Sha
Yichun Xie
International School of Software Wuhan University Wuhan, P.R. China
[email protected]
Department of Geography and Geology Eastern Michigan University Ypsilanti, USA
[email protected] Generally, two data models can be utilized to provide end users a virtual world through GIS systems, vector data model and raster data model, with each owning its pros and cons [4]. Raster data is an abstraction of the real world where spatial data is expressed as a matrix of cells or pixels. Recently, with the advances made in remote sensing, more highly qualified raster (image) datasets are become available and being put into use. Among all those usable image datasets, Pictometry image warehouse distinguishes it from other aerial photography or satellite imagery due to its high spatial resolution and georeferenced oblique images (images were taken at different angles) [5]. The related software both for desktop program (e.g. Electronic Field Study or EFS) and SDK (Software Development Kit) for building web applications is available to develop potential applications of Pictometry® 1imagery (see http://www.pictometry.com). Broadly speaking, information system that takes spatial and nonspatial information under its management and that provides functionalities from basic application such as data manipulation to advanced application such as data analysis can be termed as Spatial Information System (SIS). In this paper, we presented architecture of integrating Pictometry image service and other geospatial web services, which enables us to view both attribute information of spatial entities and the entities of interest with very high spatial resolution images from different angles. By integrating the different geospatial web services under the proposed architecture, various practical applications could be quickly built by taking the advantage of sharing the designed geospatial web services and the Pictometry image warehouse.
Abstract—People are more willing to use visual experience to help their routine work nowadays. The great success of Google map has raised user expectations about geovisualization. In this paper, we presented a web-based architecture for integrating geospatial web services with Pictometry® imagery flown by Pictometry International Corporation (Inc.). Pictometry® imagery enables us to view the land surface of interest with very high spatial resolution images from different angles (oblique or ortho image). By integrating Pictometry image service and other geospatial web services under the proposed architecture, we developed two Spatial Information Systems (SIS), Detroit Public School Facilities and Land Management Information System (DPS-FLMIS) Detroit Facility and City Engineering Management System (Detroit FCEMS), which could be used by end users to facilitate their routine work by taking the advantage of both the online interactive map manipulation and the high resolution images extracted from Pictometry image warehouse. The architecture, characterized by its flexibility and powerfulness in terms of building new SISs, integrates different geospatial web services and can also be applied in many other fields, which makes it possible to reuse the available resources of spatial information services Keywords-geovisualization; geospatial web service; spatial information systems; pictometry
I.
GEOVISUALIZATION & PICTOMETRY® IMAGERY
It has been reported that more than 80% of our existing data are spatially related, indicating that most information in the reality has something to do with locations [1]. For instance, to describe a river, we may need to record the river location, usually through a series of coordinates. Compared with those spatially related data, there is another type of data which is referred to as non-spatial data since those data are purely a description of phenomena with no spatial concept. To vividly present the data, Geographic Information System (GIS) provides a critical framework to integrate both spatial data and non-spatial data. The techniques used in presenting the real world are the key focuses of geovisualization and thus become an important field in GIS research [2]. As defined by ESRI [3], geovisualization is “working with maps and other views of the geographic information including interactive maps, 3D scenes, summary charts and tables, time-based views, and schematic views of network relationships”.
978-0-7695-3570-8/09 $25.00 © 2009 IEEE DOI 10.1109/WCSE.2009.113
II.
GEOSPATIAL WEB SERVICE
Service-based program is a popular software architecture that integrates different systems into one over network, generally including a client and server that communicate through XML messages that follow the SOAP (Simple Object Access Protocol) standard, via an interface described in WSDL (Web Service Description Language). Servicebased programs support data interoperability and can greatly improve the extensibility of software [6]. In most cases, since service-based programs are designed for the interoperability over Internet, they are always referred to as Web Services. To support spatial data interoperability, 1
Pictometry® is a registered trademark of Pictometry International Corporation
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geospatial web services can be adopted which is a kind of service-based program with the functionalities supporting spatial data analysis and representation [7]. For example, Web Map Service (WMS) is an Open Geospatial Consortium (OGC) Web Service model that provides multi-platform interoperability of spatial data set (http://www.opengeospatial.org/standards/wms). Google map provides a kind of geospatial service to integrate Google map into other applications through its APIs (http://www.google.com/apis/maps/). Similarly, Pictometry has SDK to support developing image services that can be integrated into other programs. By building geospatial web services, different functionalities and spatial data can be easily integrated over network. In many applications, data may be pulled in from different sources and are grouped based on specific themes under different applications. Following this line, Pictometry images, as a very high spatial resolution data capable of showing detailed information on ground surface, can be delivered by web service over Internet and integrated with other spatial data provided by other geospatial web services. Thus, different applications spatially sitting at different locations can be easily assembled when both Pictometry image service and geospatial web services are remotely available. III.
Geospatial web service 1
Geospatial web service 2
Geospatial web service n
Pictometry image service
WAN/Internet End users
Customized Application 1 (with local data)
Customized Application 2 (with local data)
Customized Application n (with local data)
Figure 1. Architecture for integrating geospatial web services and Pictometry image service
INTEGRATION OF GEOSPATIAL WEB SERVICES WITH PICTOMETRY IMAGE SERVICE
A. A web-based architecture A series of functionalities are encapsulated within each geospatial web service that can be used to access spatial data and make spatial analysis since many spatial data resources may distributed at different locations. Similarly, Pictometry® imagery is accessed through a Pictometry image service that can be called by standard SOAP requests. As illustrated in Fig. 1, different geospatial web services, including the Pictometry image service, can be visited and thus are reused over Wide Area Network (WAN) or Internet by various applications (customized applications). This architecture greatly improves the flexibility and decrease the cost of building different SISs. As can be seen in Fig. 1, with Pictometry image service and other geospatial web services available over the network, dozens of applications can be customized by consuming the data and functionalities provided by the web services. Fig.1 also shows that local data can be integrated with remote data pulled in from the web services. For Pictometry® imagery, the most frequent functionality requested by customized applications is extracting image for certain area of interest. Correspondingly, the following parameters are defined in image extraction function: lat: latitude for the centroid of interested area; lon: longitude for the centroid of interested area; wMap: width for the returned image hMap: heigth for the returned image scaleIndx: the scale of the returned image to be shown
(a)
(b) Figure 2. Pictometry® web viewer for various applications (a): logical model for sharing Pictometry image web viewer (b): the user interface of Pictometry image web viewer Functional sections: 1- setting image scale; 2- moving image; 3- setting image type (oblique image by clicking N-North, E-East, W-West or SSouth, or ortho image by clicking the cross icon in the center); 4- image center location; 5- setting image size (big, standard and small).
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vFrom: an oblique type of returned image (oblique image from certain angle, or an ortho image) Any SOAP request from customized applications for Pictometry images must specify the values for those parameters in order to correctly extract the corresponding result.
Pictometry image service after they are wrapped into SOAP formatted request. The request then triggers a SOAP response from the Pictometry image service which is then parsed by the viewer to represent the returned Pictometry images for customized applications. IV.
B. Pictometry image web viewer The web viewer for Pictometry® imagery developed here is a front-end program that is powered by the above mentioned Picometry image service to represent corresponding images as the back-end program. It serves as a middleware between the Pictometry image service and customized applications. As the web viewer is a web-based program that accepts standard URL request over WAN or Internet, it is convenient to share the viewer by different customized applications (Fig. 2(a)). The web viewer has a flexible web-based functional interface enabling end users to view Pictometry® imagery based on their needs (Fig. 2(b)). Those functions include some parameter setting such as the location for the image, image scale, image size, image viewing angle, and moving image. Potentially, other advanced applications such as measuring (distance, area, and elevation) make on Pictometry® imagery can also be developed, though we at present have not finished this yet. The parameters set through the viewer will be passed to the
APPLICATIONS
In this section, we presented two typical SIS applications that take the advantage of the architecture of integrating different geospatial web services. A. Detroit Public School Facilities and Land Management Information System Detroit Public School Facilities and Land Management Information System (DPS-FLMIS) was developed to market school buildings that are available for sale or lease by the District due to falling student enrollments. The website presents information of school buildings on sale or lease in a geographic context that provides information such as building photographs, floor plans, building footprints, and aerial photography to show the surrounding neighborhoods. In addition, query functions were designed to help interested parties quickly find properties that meet their selection criteria.
Figure 3. Application of DPS-FLMIS based on integration of geospatial web services The above figure here shows that a vacant building, CHANDLER Elementary, was under lease. By integrating different geospatial web services, the website not only provided the basic information such as the location, size and annual rent of the building of interest but also provided the neighborhood environment through the developed Pictometry® imagery service. (The website can be accessed through http://geodata.acad.emich.edu/realestate and is used for demo purpose only)
The main functions of the website were developed on the platform of ESRI ArcIMS (http://www.esri.com). ArcIMS supports WMS service which could be consumed by its
client applications, e.g. DPS-FLMIS. Thus, ArcIMS powered map service was integrated with Pictometry image web viewer in this case. By integrating Pictometry image web 29
viewer, the website provided functions that allow the user to view Pictometry oblique and orthor images for a property by selecting a school building from the properties list (Fig. 3). The area shown from the returned image shows the surrounding neighborhood, within a certain mile radius of the selected building. For those interested in buying or leasing real estate properties, they will not need to take time going to the field as far as the neighborhood environment is concerned.
on the rejuvenation of Detroit neighborhoods and concentrating on improving such basic quality of life issues as cleanliness, safety and beautification by removing dangerous buildings and cleaning-up illegal dump sites. This application allows Department of Public Works staff to map, maintain and report on the status of critical neighborhood data pertaining to 1) burned-out street lights 2) dangerous buildings and 3) illegal dump sites. In fact, the tools deployed on this website can also be possibly used to manage features such as trees, fire hydrants, street signs and many others. The ability to call Pictometry® imagery for any location in Detroit demonstrates a unique feature of this website. With the help of high resolution Pictometry® imagery, it is possible to quickly view different kinds of features of interest from various angles with the support from Pictometry oblique and ortho images. Fig. 4 shows the location of a dangerous building and its neighborhood environment through Pictometry® imagery.
B. Detroit Facility and City Engineering Management System Detroit Facility and City Engineering Management System (Detroit FCEMS) is aiming at providing a web-based software framework that take the advantage of GIS and high resolution Pictometry image warehouse to help local municipal management staff to improve city environment. This prototype website was also developed on the platform of ArcIMS to assist with the Mayor’s “Next Detroit Neighborhood Initiative” which is a five-year plan focusing
Figure 4. Detroit FCEMS, a case study of integrating different geospatial services The figure above shows the location of a dangerous building. Notice the red crosses on both the Pictometry image web viewer and the application map are spatially associated and points to the same location. Pictometry® imagery provided a clear view of the neighborhood environment for the building. (The website can be accessed through http://geodata.acad.emich.edu/mayordashboard and is used for demo purpose only)
V.
Pictometry® imagery. As most of the web-based applications need spatial data support, we suggest using geospatial web services to manipulate spatial data, with the intention of building extensible applications. Accordingly, different geospatial web services, including the web viewer for Pictometry® imagery powered by the Pictometry image service, can be flexibly assembled to create new applications. One of the key features in the assembled applications is that Pictometry® imagery can be assessed through its web viewer. For example, we could build both DPS-FLMIS and Detroit FCEMS sharing the same Pictometry image web viewer without the need to develop the viewer repeatedly.
CONCLUSION AND FUTURE WORK
This paper presents the method and applications of integrating geospatial web services with Pictometry® imagery. To support web-based applications with Pictometry® imagery, a web viewer for Pictometry® imagery, powered by Pictometry image service, was developed and integrated into different web-based applications to provide clear neighborhood environment, as the high resolution Pictometry® imagery can be easily called and shown with satisfactory geovisualization for end users. The viewer offers different operation functionalities to view
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One of the differences of the current proposed architecture to the popular Google map is that the former one can be very flexible and powerful in terms of its functionalities. The end applications can consume different geospatial web services based on the actual needs, which makes it flexible. Moreover, the proposed architecture can provide more powerful functions. For example, in the case study of DPS-FLMIS, we can easily query different information based on the attribute information of spatial entities (e.g., buildings). Therefore, while Google map is very useful for public especially in areas of transportation information query, our proposed architecture mainly can provide special service in particular applications. Though the web viewer for Pictometry® imagery developed here makes it possible for web-based integration of geospatial web services with Pictometry® imagery, some improvements for the Pictometry image web viewer need to be made in the future to better use of this valuable data. First, the current Picotmetry image warehouse is a file-based system. In other words, the imagery dataset is organized in separate tiles and the viewer developed here can only fetch one tile each time. Under some circumstances, it may need two or more adjacent tiles jointed together to provide a wide view of the neighborhood environment. Second, performance needs to be further improved especially when the called image is shown in small scale.
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ACKNOWLEDGMENT This research is partially funded by Open Research Fund Program of key GIS Laboratory of China’s Education Ministry (WD2006-10).
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