**5. Potential application areas**

More than ten years ago, Al Gore articulated a vision of 'Digital Earth' as a multi-resolution, three-dimensional representation of the planet that would make it possible to find, visualise, and make sense of vast amounts of geo-referenced information on the physical and social environment (Gore 1998, for a comprehensive discussion see Craglia et al. 2008). Google Earth, NASA World Wind and other geo-browsers brought high resolution imagery to hundreds of millions of internet users and a major industry developed ways to explore data geographically, and visualise overlaid information provided by both the public and private sectors, as well as citizens who volunteer new data (Goodchild, 2007).

Generally speaking, fine-grained urban sensing greatly enhances our knowledge of the environment by adding objective and non-visible data layers in real-time (Resch et al., 2008). In other words, these systems help us increase our capacity to observe and understand the city, and the impacts on and by society. This seems to be a very desirable state because more

Standardised Geo-Sensor Webs for Integrated Urban Air Quality Monitoring 525

Ubiquitous and continuous environmental monitoring is an enormous challenge, and this is particularly true in the urban context, which poses very specific challenges as well technologically as socially and politically. In this chapter we discussed several of these issues, and outlined how our approach can meet future requirements for urban sensing. The focus is to contribute to a 'complete' picture of a living city for decisions makers, planners and operators beyond locational analysis. This may be seen distinct from a number of citizen-centred sensor approaches and context-aware systems. While a number of peoplecentric pervasive sensing systems are notable successes (Campbell et al. 2006), most of these examples focus on localising people and objects in a dened environment to enable context aware applications. In such projects, the notion of sensing is conned to supporting location-based context-awareness. In our *Live Geography* approach a more general integrated sensing architecture to support the diversity of applications and hardware platforms has

Based on the Live Geography approach, we outlined the Common Scents concept, which tries to establish an interoperable, modular and flexible sensing and data analysis infrastructure, as opposed to hitherto monolithic sensor networks. To prove our system's portability, we did implementations in two different pilot deployments (Cambridge, MA US and Copenhagen, Denmark) using the same data integration and analysis infrastructure. Further exploitation of this approach is planned for other cities. We see more future challenges in the socio-political domain rather in the technological development necessary. It becomes more and more obvious that a cross-disciplinary group of researchers and technologists needs to persistently interact with end users. Only then we may achieve a wide appreciation of sensing which is needed to support future civic, cultural, and community life in cities. In many parts of the world, notably Germany and some Western European countries, attempts to 'completely' map cities are very sensitive. Google faces great problems with its StreetView approach. An integrated Common Scents must provide a clearly recognisable benefit to the citizens in order to be appreciated by all societal groups. Public Health applications may have a good chance to get accepted although some of the capabilities, for instance the ability to measure remotely the conditions of people in real time, raise social concerns centred on privacy issues. Methods for sensor data fusion and designs for human-computer interfaces are both crucial for the full realisation of the

We also believe that the impact of pervasive sensing in the city has to be carefully assessed. We found that e.g. providing very fine-grained information layers might on the one hand be a powerful decision support instrument, but on the other hand too detailed environmental information might also have negative effects. As the term 'air quality' is just a surrogate for more personal impacts such as life expectation or respiration diseases, this information could yield a very broad impact in various kinds of areas such as housing market, the

As the Common Scents concept has been developed and implemented together with the Public Health Department of the City of Cambridge, MA US as concrete end users, we believe that our approach can respond to dedicated needs of the city management. Therefore, the longer-term goal is to enhance people's perception of their environment by adding unseen information layers and thus changing their short-term behaviour by

**6. Conclusion** 

been developed.

potential of integrated and pervasive sensing.

insurance sector or urban planning in general.

providing real-time decision support.

accurate data about local air temperature, atmospheric humidity, gaseous and particulate air pollution, and traffic emissions can positively influence areas such as public health, traffic management or emergency response. Apart from this information enrichment, accurate sensor measurements also have a much broader influence: considering for example that 'air quality' is only a surrogate for the effects of pollutants on humans makes a fine-grained air quality map a very sensitive information layer, as discussed in section 4.

Within the Common Scents project, we focus on the use case of air quality monitoring for use in the public health sector. However, we designed the monitoring infrastructure in such a modular way that it is not bound to one single application area. Below, several practically motivated fields of real-world applications are described, which could use the same infrastructure presented in section 3.

Public Health has been asked to participate in policymaking on 'quality of life' issues increasingly over the past decade. The superimposing of the medical model to describe the impact of conditions that have traditionally been regarded as nuisances has created a great challenge, particularly in the field of environmental health.

One pollutant often used to serve as a proxy is NOx, which technically represents various gaseous species comprised of oxygen and nitrogen molecules. Another indicator of nearroadway effects that has gained recent attention is ultrafine particulates (UFPs), particles that are less than 0.1 microns (100 nm) in diameter. Thus, air quality measurements of hazardous air pollutants can be widely associated with traffic (non-point sources). A pervasive sensor network could help capture measurements in high spatial and temporal resolution to take short-term measures (dynamically adapt traffic management or send out alerts to citizens in case of threshold exceedance). Also, it could support traditional longterm studies on the impact of certain pollutants on public health.

The use case of noise mapping has received a lot of attention recently. Many disputes within the research field emerge from noise impacts associated with construction, excavation or some other commercial or industrial enterprise. These disputes also arise from use of domestic landscaping equipment, like leaf blowers and snow blowers. The limits imposed by the city on noise generation are intended to assess the background noise levels. A source cannot be held responsible for noise levels that exceed the city's allowable limits if the ambient noise in that area already exceeds those limits. The development of noise 'maps' may not immediately result in satisfaction from aggrieved residents, but it can be used to consider the noise impact of future development and zoning policies. It may also contribute to efforts to reduce the number of cars travelling across the city by adding the noise impact dimension to the discussion. This is much more likely to be given full consideration if it can be demonstrated with highly resolved data maps, which can be generated in near real-time using the Common Scents infrastructure.

The urban heat island effect describes the contribution of the built environment to the ambient temperature within urban areas. While this is not likely to become a primary public health concern, it has great bearing on efforts to limit the loss of heating energy across the city. Different agencies have been established to work on a long-term strategy to reduce overall energy use (e.g. Cambridge Energy Alliance: http://www.cambridgeenergyalliance.org) and to encourage individual homeowners and building owners to evaluate their energy loss. It is quite possible that small changes in heat loss, as described through a detailed heat map of the city over time, could show progress towards energy efficiency in a materials way. This could be used both as an evaluation tool in tracking the city's progress, and as a means to engage the public in the energy goals of the community.
