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Analyzing Performances of Different Atmospheric Correction Techniques for Landsat 8: Application for Coastal Remote Sensing

Peer reviewed: 
Yes, item is peer reviewed.
Date created: 
2019-02-25
Abstract: 

Ocean colour (OC) remote sensing is important for monitoring marine ecosystems. However, inverting the OC signal from the top-of-atmosphere (TOA) radiance measured by satellite sensors remains a challenge as the retrieval accuracy is highly dependent on the performance of the atmospheric correction as well as sensor calibration. In this study, the performances of four atmospheric correction (AC) algorithms, the Atmospheric and Radiometric Correction of Satellite Imagery (ARCSI), Atmospheric Correction for OLI ‘lite’ (ACOLITE), Landsat 8 Surface Reflectance (LSR) Climate Data Record (Landsat CDR), herein referred to as LaSRC (Landsat 8 Surface Reflectance Code), and the Sea-Viewing Wide Field-of-View Sensor (SeaWiFS) Data Analysis System (SeaDAS), implemented for Landsat 8 Operational Land Imager (OLI) data, were evaluated. The OLI-derived remote sensing reflectance (Rrs) products (also known as Level-2 products) were tested against near-simultaneous in-situ data acquired from the OC component of the Aerosol Robotic Network (AERONET-OC). Analyses of the match-ups revealed that generic atmospheric correction methods (i.e., ARCSI and LaSRC), which perform reasonably well over land, provide inaccurate Level-2 products over coastal waters, in particular, in the blue bands. Between water-specific AC methods (i.e., SeaDAS and ACOLITE), SeaDAS was found to perform better over complex waters with root-mean-square error (RMSE) varying from 0.0013 to 0.0005 sr−1 for the 443 and 655 nm channels, respectively. An assessment of the effects of dominant environmental variables revealed AC retrieval errors were influenced by the solar zenith angle and wind speed for ACOLITE and SeaDAS in the 443 and 482 nm channels. Recognizing that the AERONET-OC sites are not representative of inland waters, extensive research and analyses are required to further evaluate the performance of various AC methods for high-resolution imagers like Landsat 8 and Sentinel-2 under a broad range of aquatic/atmospheric conditions.

Document type: 
Article
File(s): 

Epidemiological and Spatial Characteristics of Interpersonal Physical Violence in a Brazilian city: A Comparative Study of Violent Injury Hotspots in Familial Versus Non-Familial Settings, 2012-2014

Peer reviewed: 
Yes, item is peer reviewed.
Date created: 
2019-01-07
Abstract: 

This study explores both epidemiological and spatial characteristics of domestic and communityinterpersonal violence. We evaluated three years of violent trauma data in themedium-sized city of Campina Grande in North-Eastern Brazil. 3559 medical and police recordswere analysed and 2563 cases were included to identify socioeconomic and geographicpatterns. The associations between sociodemographic, temporal, and incidentcharacteristics and domestic violence were evaluated using logistic regression. Using GeographicalInformation Systems (GIS), we mapped victims’ household addresses to identifyspatial patterns. We observed a higher incidence of domestic violence among female,divorced, or co-habitant persons when the violent event was perpetrated by males. Therewas only a minor chance of occurrence of domestic violence involving firearms. 8 out of 10victims of domestic violence were women and the female/male ratio was 3.3 times greaterthan that of community violence (violence not occurring in the home). Unmarried coupleswere twice as likely to have a victim in the family unit (OR = 2.03), compared to married couples.Seven geographical hotspots were identified. The greatest density of hotspots wasfound in the East side of the study area and was spatially coincident with the lowest averagefamily income. Aggressor sex, marital status, and mechanism of injury were most associatedwith domestic violence, and low-income neighbourhoods were coincident with bothdomestic and non-domestic violence hotspots. These results provide further evidence thateconomic poverty may play a significant role in interpersonal, and particularly domesticviolence.

Document type: 
Article
File(s): 

Photodegraded dissolved organic matter from peak freshet river discharge as a substrate for bacterial production in a lake-rich great Arctic delta

Peer reviewed: 
Yes, item is peer reviewed.
Date created: 
2018-03-27
Abstract: 

Lake-rich Arctic river deltas are recharged with terrigenous dissolved organic matter (DOM) during the yearly peak water period corresponding with the solstice (24 h day−1 solar irradiance). Bacteria-free DOM collected during peak Mackenzie River discharge was exposed to sunlight for up to 14 days in June 2010. As solar exposure increased, carbon and lignin concentrations declined (10% and 42%, respectively, after 14 days), as did DOM absorptivity (62% after 14 days), aromaticity, and molecular weight. Photochemical changes were on par with those normally observed in Mackenzie Delta lakes over the entire open-water season. When irradiated freshet DOM was provided as a substrate, no significant differences were observed in community-level metabolism among five bacterial communities from representative delta habitats. However, bacterial abundance was significantly greater when nonirradiated (0 day) rather than irradiated DOM (7 or 14 days) was provided, while cell-specific metabolic measures revealed that per-cell bacterial production and growth efficiency were significantly greater when communities were provided irradiated substrate. This complex response to rapid DOM photodegradation may result from the production of inhibitory reactive oxygen species (ROS), along with shifts in bacterial community composition to species that are better able to tolerate ROS, or metabolize the labile photodegraded DOM.

Document type: 
Article

Supplemental information for Jorge M. G. et al., Subjectivity of drumlin manual mapping and inter-mapper differences in derived morphometrics.

Peer reviewed: 
No, item is not peer reviewed.
Date created: 
2017-02-14
Abstract: 

Supplemental data for Jorge M. G. et al, Subjectivity of drumlin manual mapping and inter-mapper differences in derived morphometrics.

S1 Table. Inter-mapper differences – results of the Wilcoxon signed-rank tests and absolute differences in morphometric medians for all pairs of mappers, for footprints from both DTMs (DTM2; DTM11).

S2 Files. The KML-format file contains the location of the mapped drumlins. The shapefile combines all the footprints mapped by the 14 mappers who participated in the study.

Document type: 
Dataset

Calculation of in-situ acoustic sediment attenuation using off-the-shelf ADCPs in low concentration settings

Peer reviewed: 
Yes, item is peer reviewed.
Abstract: 

The use of ‘off-the-shelf’ acoustic Doppler velocity profilers (ADCPs) to estimate suspended sediment concentration and grain size in rivers requires robust methods to estimate sound attenuation by suspended sediment. Theoretical estimates of sediment attenuation require a priori knowledge of the concentration and grain size distribution (GSD), making the method impractical to apply in routine monitoring programs.  In-situ methods use acoustic backscatter profile slope to estimate sediment attenuation, and are a more attractive option.  However, the performance of in-situ sediment attenuation methods has not been extensively compared to theoretical methods.  We used three collocated horizontally mounted ADCPs in the Fraser River at Mission, British Columbia and 298 observations of concentration and GSD along the acoustic beams to calculate theoretical and in-situ sediment attenuation. Conversion of acoustic intensity from counts to decibels is influenced by the instrument noise floor, which affects the backscatter profile shape and therefore in-situ attenuation.  We develop a method that converts counts to decibels to maximize profile length, which is useful in rivers where cross-channel acoustic profile penetration is a fraction of total channel width. Nevertheless, the agreement between theoretical and in-situ attenuation is poor at low concentrations because cross-stream gradients in concentration, sediment size or GSD can develop, which affect the backscatter profiles.  So we establish threshold concentrations below which in-situ attenuation is unreliable in Fraser River. Results call for careful examination of cross-stream changes in suspended sediment characteristics and acoustic profiles across a range of flows before in-situ attenuation methods are applied in river monitoring programs. 

Document type: 
Dataset

They Go the Extra Mile, the Extra Ten Miles...”: Examining Canadian Medical Yourists’ Interactions with Health Care Workers Abroad

Peer reviewed: 
Yes, item is peer reviewed.
Date created: 
2015
Abstract: 

Developing an understanding of medical tourists' interactions with their health care workers while abroad is important for a number of reasons. Social support has been linked to improved health outcomes for patients (Berkman et al., 2000; Lee and Rotheram-Borus, 2001; Uchino, 2004, 2006), while a lack of social support has been found to lead to higher mortality rates (Brummett et al., 2001; Rutledge et al., 2004). While abroad, medical tourists are not in a position to draw on their usual social support networks as they are away from home. It could be the case that workers in medical tourism facilities are aware of this and work to form a supportive and trusting bond with the patients given that they are away from home and unable to draw on their usual support networks. Furthermore, when patients perceive their relationship with their health care workers as positive, they have been shown to have a higher chance of improved health outcomes (Stewart et al., 2000; Arora, 2003; Beach et al., 2006; Street et al., 2009). There is no reason to think this would be any different for medical tourists. The patient-health care worker relationship can have important implications for patient health and therefore we believe that research into this topic using medical tourists' own experiential accounts can help to identify strategies that can be used to secure and improve this relationship.

Document type: 
Book chapter
File(s): 

Medical Tourism in Barbados: Negotiating Inherent Tensions

Peer reviewed: 
Yes, item is peer reviewed.
Date created: 
2015
Abstract: 

This chapter draws on our long term-research program examining medical tourism in Barbados and the wider Anglophone Caribbean. Since 2011 we have undertaken 69 semi-structured interviews and three focus groups with a wide range of health system and tourism sector stakeholders in Barbados, compiled a comprehensive collection of state and media reports discussing medical tourism, and collectively spent over a year conducting on-site ethnographic fieldwork that has included many informal conversations with users of the Barbadian health system from a wide range of backgrounds. Together, these datasets and experiences provide a rich understanding of the potential considerations and hopes arising from the ongoing discussion about medical tourism development in a small island setting. Exploring these considerations and hopes suggests ways in which Barbados and other small island states seeking to develop their medical tourism sectors can negotiate a structure for medical tourism that can best meet their development goals.

Document type: 
Book chapter
File(s): 

A Comparative Analysis of Potential Spatio-Temporal Access to Palliative Care Services in Two Canadian Provinces

Peer reviewed: 
Yes, item is peer reviewed.
Date created: 
2015
Abstract: 

Background

Access to health services such as palliative care is determined not only by health policy but a number of legacies linked to geography and settlement patterns. We use GIS to calculate potential spatio-temporal access to palliative care services. In addition, we combine qualitative data with spatial analysis to develop a unique mixed-methods approach.

Methods

Inpatient health care facilities with dedicated palliative care beds were sampled in two Canadian provinces: Newfoundland and Saskatchewan. We then calculated one-hour travel time catchments to palliative health services and extended the spatial model to integrate available beds as well as documented wait times.

Results

26 facilities with dedicated palliative care beds in Newfoundland and 69 in Saskatchewan were identified. Spatial analysis of one-hour travel times and palliative beds per 100,000 population in each province showed distinctly different geographical patterns. In Saskatchewan, 96.7 % of the population living within a-1 h of drive to a designated palliative care bed. In Newfoundland, 93.2 % of the population aged 65+ were living within a-1 h of drive to a designated palliative care bed. However, when the relationship between wait time and bed availability was examined for each facility within these two provinces, the relationship was found to be weak in Newfoundland (R2 = 0.26) and virtually nonexistent in Saskatchewan (R2 = 0.01).

Conclusions

Our spatial analysis shows that when wait times are incorporated as a way to understand potential spatio-temporal access to dedicated palliative care beds, as opposed to spatial access alone, the picture of access changes.

Document type: 
Article
File(s): 

Inbound Medical Tourism to Barbados: A Qualitative Examination of Local Lawyers’ Prospective Legal and Regulatory Concerns

Peer reviewed: 
Yes, item is peer reviewed.
Date created: 
2015
Abstract: 

Background

Enabled by globalizing processes such as trade liberalization, medical tourism is a practice that involves patients’ intentional travel to privately obtain medical care in another country. Empirical legal research on this issue is limited and seldom based on the perspectives of destination countries receiving medical tourists. We consulted with diverse lawyers from across Barbados to explore their views on the prospective legal and regulatory implications of the developing medical tourism industry in the country.

Methods

We held a focus group in February 2014 in Barbados with lawyers from across the country. Nine lawyers with diverse legal backgrounds participated. Focus group moderators summarized the study objective and engaged participants in identifying the local implications of medical tourism and the anticipated legal and regulatory concerns. The focus group was transcribed verbatim and analyzed thematically.

Results

Five dominant legal and regulatory themes were identified through analysis: (1) liability; (2) immigration law; (3) physician licensing; (4) corporate ownership; and (5) reputational protection.

Conclusions

Two predominant legal and ethical concerns associated with medical tourism in Barbados were raised by participants and are reflected in the literature: the ability of medical tourists to recover medical malpractice for adverse events; and the effects of medical tourism on access to health care in the destination country. However, the participants also identified several topics that have received much less attention in the legal and ethical literature. Overall this analysis reveals that lawyers, at least in Barbados, have an important role to play in the medical tourism sector beyond litigation – particularly in transactional and gatekeeper capacities. It remains to be seen whether these findings are specific to the ecology of Barbados or can be extrapolated to the legal climate of other medical tourism destination countries.

Document type: 
Article
File(s): 

Suburbanisation of Oral Cavity Cancers: Evidence From a Geographically-Explicit Observational Study of Incidence Trends in British Columbia, Canada, 1981–2010

Peer reviewed: 
Yes, item is peer reviewed.
Date created: 
2015
Abstract: 

Background

Recent studies have demonstrated an elevated risk of oral cavity cancers (OCC) among socioeconomically deprived populations, whose increasing presence in suburban neighbourhoods poses unique challenges for equitable health service delivery. The majority of studies to date have utilised aspatial methods to identify OCC. In this study, we use high-resolution geographical analyses to identify spatio-temporal trends in OCC incidence, emphasising the value of geospatial methods for public health research.

Methods

Using province-wide population incidence data from the British Columbia Cancer Registry (1981–2009, N  = 5473), we classify OCC cases by census-derived neighbourhood types to differentiate between urban, suburban, and rural residents at the time of diagnosis. We map geographical concentrations by decade and contrast trends in age-adjusted incidence rates, comparing the results to an index of socioeconomic deprivation.

Results

Suburban cases were found to comprise a growing proportion of OCC incidence. In effect, OCC concentrations have dispersed from dense urban cores to suburban neighbourhoods in recent decades. Significantly higher age-adjusted oral cancer incidence rates are observed in suburban neighbourhoods from 2006 to 2009, accompanied by rising socioeconomic deprivation in those areas. New suburban concentrations of incidence were found in neighbourhoods with a high proportion of persons aged 65+ and/or born in India, China, or Taiwan.

Conclusions

While the aging of suburban populations provides some explanation of these trends, we highlight the role of the suburbanisation of socioeconomically deprived and Asia-born populations, known to have higher rates of risk behaviours such as tobacco, alcohol, and betel/areca consumption. Specifically, betel/areca consumption among Asia-born populations is suspected to be a primary driver of the observed geographical shift in incidence from urban cores to suburban neighbourhoods. We suggest that such geographically-informed findings are complementary to potential and existing place-specific cancer control policy and targeting prevention efforts for high-risk sub-populations, and call for the supplementation of epidemiological studies with high-resolution mapping and geospatial analysis.

Document type: 
Article
File(s):