Data Collection and Aggregation in Mobile Sensing

Nowadays, smartphones have become ubiquitous and are playing a critical role in key aspects of people\u27s daily life such as communication, entertainment and social activities. Most smartphones are equipped with multiple embedded sensors such as GPS (Global Positioning System), accelerometer, camera, etc, and have diverse sensing capacity. Moreover, the emergence of wearable devices also enhances the sensing capabilities of smartphones since most wearable devices can exchange sensory data with smartphones via network interfaces. Therefore, mobile sensing have led to numerous innovative applications in various fields including environmental monitoring, transportation, healthcare, safety and so on. While all these applications are based on two critical techniques in mobile sensing, which are data collection and data aggregation, respectively. Data collection is to collect all the sensory data in the network while data aggregation is any process in which information is gathered and expressed in a summary form such as SUM or AVERAGE. Obviously, the above two problems can be solved by simply collect all the sensory data in the whole network. But that will lead to huge communication cost. This dissertation is to reduce the huge communication cost in data collection and data aggregation in mobile sensing where the following two technical routes are applied. The first technical route is to use sampling techniques such as uniform sampling or Bernoulli sampling. In this way, an aggregation result with acceptable error can be can be calculate while only a small part of mobile phones need to submit their sensory data. The second technical rout is location-based sensing in which every mobile phone submits its geographical position and the mobile sensing platform will use the submitted positions to filter useless sensory data. The experiment results indicate the proposed methods have high performance

Valuing Coastal Risk with Revealed and Stated Preference Methods

Developed coastlines provide a variety of recreation opportunities to coastal residents and visitors but are also the first line of defense for oceanfront development against chronic hazards like erosion and sea level rise. In the Pacific Northwest of the United States, oceanfront homes also face an additional severe but very low frequency acute hazard: a Cascadia Subduction Zone earthquake and tsunami. These chronic and acute coastal hazards pose a challenge for policymakers because they often create conflicting interests. This dissertation is composed of two essays on issues of acute and chronic coastal risk in Oregon. The first essay investigates the impact of information shocks about tsunami risk on coastal residents’ risk perceptions, as capitalized into property prices. We use revealed preference methods to examine the coastal Oregon housing market response to three sets of tsunami risk signals: two exogenous events, a hazard planning change, and the addition of visual cues of tsunami risk in residential neighborhoods. The potential housing market impacts identified in these analyses suggest that risk signals about a high severity but low frequency acute hazard can be salient to coastal residents. These findings suggest that Oregon policymakers and emergency managers may be able to use risk signals to induce individuals to pay attention to and prepare more for a Cascadia Subduction Zone event. In the second essay, we develop a combined revealed and stated preference survey and collect survey data from Oregon households. We use this data to estimate stated preference models and measure Oregon residents’ willingness to pay for coastal erosion management conditional on differences in shoreline armoring policy for private oceanfront landowners. Results are suggestive of significant welfare gains stemming from a coastal management plan that would provide funding for sediment management to preserve safe recreation access on developed Oregon beaches. We do not find evidence of a significant difference between how much Oregon residents are willing to pay for a policy scenario where the existing shoreline armoring policy (Goal 18) is relaxed to allow more armoring of private property and a policy scenario where the existing armoring policy is maintained in its current form. Overall, these two essays contribute new information about Oregon residents’ perceptions and preferences regarding acute and chronic coastal risk. These findings can help inform policies in both emergency and resource management