How do people perceive the disclosure risk of maps? Examining the perceived disclosure risk of maps and its implications for geoprivacy protection

ABSTRACT

This research examines how people subjectively perceive the disclosure risk of a map using original data collected in an online survey with 856 participants. The results indicate that perceived disclosure risk increases as the amount of locational information displayed on a map increases. Compared to point-based maps, perceived disclosure risk is significantly lower for kernel density maps, convex hull maps, and standard deviational ellipse maps. The results also revealed that perceived disclosure risk is affected by map scale and the presence of information of other people on a map. For geomasking methods, perceived disclosure risk decreases as aggregation level increases and as relocation distance increases. However, aggregation methods (point to polygon) are more effective in preventing the re-identification of individuals when compared to relocation methods (point to point). Lastly, the perceived disclosure risk of a map that displays socially-vulnerable people is significantly higher than that of a map that displays non-vulnerable groups. Specifically, a map displaying the private locations of elementary school students has the highest perceived disclosure risk. Based on the results, a set of geoprivacy protection guidelines for mapping people’s private locations to minimize people’s perceived disclosure risk is proposed. Implications for mapping infectious diseases like the COVID-19 are also discussed.     

Genetic variation in Avicennia marina in three estuaries of Sydney (Australia) and implications for rehabilitation and management

In order to ensure conservation of mangroves, genetic diversity in remaining populations must be explored. Both morphological and isozyme analyses were used and compared in investigating the intra- and inter-estuarine variation in Avicennia marina in Sydney, the most urbanised area in Australia. Sediment characteristics, metal levels, tree attributes, leaf morphology and isozyme/allozyme analyses were conducted. Tree characteristics did not prove to be adequate genetic markers, but leaf morphology may be of use in this species. Isozyme/allozyme analyses indicated that genetic distance corresponded with geographic distance, although habitat metal levels may indicate local selection pressures. High levels of heterozygote deficiencies were displayed in each estuary, which could threaten future viability. The results hold implications for management as periodic isozyme analysis may be useful in indicating management needs. The identification of metal-tolerant types may also be useful. Transplantation among estuaries may assist in increasing genetic diversity, if considered desirable. Whatever the management aims, isozyme/allozyme analyses are shown to be useful for revealing genetic diversity in this species.     

Growing up with rivers? Rivers in London children's worlds

This paper presents the results from exploratory research which set out to investigate London children's perceptions and uses of river environments. Mainly qualitative, multi-method research was carried out in four primary schools with children aged 9–11, focusing on two rivers near to the schools. Rivers were found to be marginal to the children's everyday lives and outdoor play, being perceived as polluted, neglected, and initially dangerous places. However, when experienced on visits observed as part of the research, some of these perceptions changed and rivers were also found to afford many special activities and experiences for the children. The visits were generally seen to have a positive effect on the children's perceptions of rivers, at least in the short term. This suggests that, if managed appropriately, rivers could be potentially rewarding play areas for children. Moreover, children could provide valuable input for river managers in suggesting ways of improving suitable local rivers for increased recreational uses.     

Semi-variograms for modelling the spatial pattern of landform and soil properties

Many geomorphic properties can be treated as spatially-dependent random variables. Some are second-order stationary, others appear to vary without bound. In these circumstances their variation is best described by the semi-variogram. In most instances the semi-variogram can be modelled by a simple mathematical function, which itself is bounded for a stationary variable and unbounded otherwise. The function must be conditional negative semi-definite to be permissible. More complex variation can be represented by combining two or more permissible models. Sample semi-variograms of several landform and soil properties illustrate the common types of semi-variogram. Their form and parameters are interpreted in physical terms.     

A Simple Reclassification Method for Correcting Uncertainty in Land Use/Land Cover Data Sets Used with Land Surface Models

With increasing computational resources, environmental models are run at finer grid spacing to resolve the land surface characteristics. The land use/land cover (LULC) data sets input into land surface models are used to assign various default parameters from a look-up tables. The objective of this study is to assess the potential uncertainty in the LULC data and to present a reclassification method for improving the accuracy of LULC data sets. The study focuses on the Southern Great Plains and specifically the Walnut River Watershed in southeastern Kansas, USA. The uncertainty analysis is conducted using two data sets: The National Land Cover Dataset 1992 (NLCD 92) and the Gap Analysis Program (GAP) data set, and a reclassification logic tree. A comparison of these data sets showed that they do not agree for approximately 27% of the watershed. Moreover, an accuracy assessment of these two data sets indicated that neither had an overall accuracy as high as 80%. Using the relationships between land-surface characteristics and LULC, a reclassification of the watershed was conducted using a logical model. This model iteratively reclassified the uncertain pixels according to their surface characteristics. The model utilized normalized difference vegetation index (NDVI) measurements during April and July 2003, elevation, and slope. The reclassification yielded a revised LULC dataset that was substantially improved. The overall accuracy of the revised data set was nearly 93%. The study results suggest: (i) as models adopt finer grid spacings, the uncertainty in the LULC data will become significant; (ii) assimilating NDVI into the land-surface models can reduce the uncertainty due to LULC assignment; (iii) the standard LULC data sets must be used with caution when the focus is on local scale; and (iv) reclassification is a valuable means of improving the accuracy of LULC data sets prior to applying them to local issues or phenomena.     

Climate, water management, and policy in the San Pedro Basin: results of a survey of Mexican stakeholders near the U.S.–Mexico border

This paper reviews regional climate knowledge and vulnerability in the northern Mexico San Pedro River Basin, with a focus on water quality, quantity, and management issues on the Mexican side of the border. A discussion based on the available literature is supplemented by a survey assessing concerns about water and the quality and usability of climate and hydrologic information available to water managers and communities. The surveys indicate that the central concern for urban residents is the lack of reliable potable water due to frequent service breakdowns–with climate change and variability, specifically drought and high temperatures, as contributing factors. Water managers desire appropriate meteorological and hydrologic information to improve planning strategies, but access to this information remains limited. Considerable disagreement exists about who should pay for previously free or low-cost water and wastewater treatment. Urban users have little incentive to conserve because of the present flat, low rate and frustration with service. In rural areas, while a majority of ranchers recognize that variable climate and water loss could increasingly jeopardize their lifestyle, they seldom use meteorological information in planning or modify their water consumption. Climate vulnerability also includes potential for serious environmental health issues due to the presence of heavy metals and organic contaminants in the San Pedro.     

Water quality along a river continuum subject to point and diffuse sources

The water quality along the River Kennet, in the Thames basin of southern England, was examined in terms of the influence of point- and diffuse-nutrient inputs. The river is supplied mainly from a Cretaceous Chalk aquifer and hence the waters are of a calcium bicarbonate type. The nitrate largely comes from agricultural sources, with concentrations decreasing downstream due to plant uptake and probable denitrification. In contrast, soluble reactive phosphorus (SRP) is largely associated with sewage inputs and concentrations increase downstream in line with effluents from major towns such as Newbury and Reading. Adjacent to the river in the lower half of the catchment is the Kennet and Avon Canal and the two are in places hydrologically connected. The canal inputs may influence calcium carbonate (calcite) precipitation and increase suspended sediment and particulate phosphorus concentrations in the river. Monitoring upstream and downstream of Marlborough sewage treatment works (STW) showed that SRP concentrations in the effluent were highly variable due to variable efficiency of P stripping and still sufficiently concentrated to dominate downstream river SRP with potential impacts on stream ecology. Biological recovery in this river following P stripping at STWs is complex and controlling those spikes in SRP that are above a threshold of 100 μg l⁻¹ may be a critical requirement. More stringent effluent targets than are currently recommended may be needed (less than 800 μg RP l⁻¹) to achieve good ecological status in this river depending on SRP concentrations upstream.