Sky Visibility Research Articles

Urban Building Updates Monitoring Based on Sky Visibility Estimation From Satellite Signals

Urban Building Updates Monitoring Based on Sky Visibility Estimation From Satellite Signals

Creating restorative corridors - Perceptual and physiological feedback of children on the audiovisual environment in primary school corridors

The corridor space of the primary school campus is frequently used for recess and relaxation by the students, which brings stress and emotional recovery from the intense academic work. How to integrate natural restorative environment into the corridor has attracted academic and practical attention. Based on Kaplan's theory of Restorative Environment, this study combined subjective evaluation with physiological feedback to explore the primary school children's perception and evaluation of corridor space, and proposed the effects of different audio-visual indicators. Based on a questionnaire survey of children's activities and restoration in two schools, the paper found the association between perceived restoration and high interaction behavior in the corridor, including floriculture and interacting with hands-on devices. The richness of amenities and colors in the corridor space had the highest correlation with children's restorative ratings, followed by interface openness and sky visibility. Natural soundscapes also had a strong correlation with children's auditory restorability. Subsequent virtual audition experiments validated above findings, suggesting the benefits of increased greenery, sky and natural sounds in reducing children's stress.

Blue skies: Does the visual composition of sky guide subjective judgments of naturalness in the environment?

Expanding on previous findings, that highlighted the significance of sky in environmental perception, our analysis investigated whether the visual composition of the sky shapes perceptions of environmental naturalness. The study employed a novel, free-selection task in which participants viewed a series of environmental images with varying levels of natural and urban elements, as well as different sky visibility conditions, and were asked to identify “nature” within these images. The task procedure also involved subjective ratings of each scene. Using previously gathered data, we reassessed 105 participants' selection of the sky as “nature” across 96 photos of diverse outdoor scenes to understand which visuospatial features influence these perceptions. Utilizing the Boruta feature selection algorithm, we identified key characteristics—fractal dimensions, brightness, and entropy in brightness, hue, and saturation—that significantly predicted the selection of sky as “nature”, irrespective of the environment type (urban or natural). Results indicated that lower fractal dimensions are preferred for sky selected as “nature”, inversely affecting the naturalness judgment of scenes with the additional effect of brightness. These findings enhance our understanding of how visuospatial features influence environmental perception, offering implications for future research directions and theoretical advancements in understanding environmental perception.

Research on Urban Street Spatial Quality Based on Street View Image Segmentation

Assessing the quality of urban street space can provide suggestions for urban planning and construction management. Big data collection and machine learning provide more efficient evaluation methods than traditional survey methods. This study intended to quantify the urban street spatial quality based on street view image segmentation. A case study was conducted in the Second Ring Road of Changsha City, China. Firstly, the road network information was obtained through OpenStreetMap, and the longitude and latitude of the observation points were obtained using ArcGIS 10.2 software. Then, corresponding street view images of the observation points were obtained from Baidu Maps, and a semantic segmentation software was used to obtain the pixel occupancy ratio of 150 land cover categories in each image. This study selected six evaluation indicators to assess the street space quality, including the sky visibility index, green visual index, interface enclosure index, public–facility convenience index, traffic recognition, and motorization degree. Through statistical analysis of objects related to each evaluation indicator, scores of each evaluation indicator for observation points were obtained. The scores of each indicator are mapped onto the map in ArcGIS for data visualization and analysis. The final value of street space quality was obtained by weighing each indicator score according to the selected weight, achieving qualitative research on street space quality. The results showed that the street space quality in the downtown area of Changsha is relatively high. Still, the level of green visual index, interface enclosure, public–facility convenience index, and motorization degree is relatively low. In the commercial area east of the river, improvements are needed in pedestrian perception. In other areas, enhancements are required in community public facilities and traffic signage.

Characterization of the precision of PPP solutions as a function of latitude and session length

Abstract This study investigates the impact of observation session duration and station latitude on the precision of Precise Point Positioning (PPP). Global Positioning System-only Receiver Independent Exchange files from 516 continuous stations spanning latitudes from 90°N to 90°S across the Americas (30°–130°W) were binned into sessions of 1, 2, 3, 4, 6, and 12 h and processed using the GPSPACE PPP software. These sub-daily solutions, along with the original 24 h ones, were compared against a reference coordinate derived from an extended linear trajectory model for each station. Analysis of the results, considering both accuracy and precision, was conducted across the entire latitude range of the study. We found that the precision of a PPP solution approximately follows a power-law relationship with observation duration. Parameters for these power-law relationships were determined for all latitude ranges that allow users to predict a result’s uncertainty as a function of session length. Findings indicate that longer observation sessions lead to reduced positioning errors, with vertical scatter decreasing with increasing latitude. Since all these stations are characterized by good to excellent sky view, our power-law rule-of-thumb provides a lower bound on the occupation time needed to achieve target positioning precision at locations with poorer sky visibility.

A study on factors influencing the spatial oppressiveness in small courtyard spaces within university residential areas

ABSTRACT A number of obstacles in terms of the growing demand for residential spaces for students in China's education industry. Changing urban development patterns often lead to densely populated, unpleasant university residential neighborhood, posing threats to the well-being of university personnel. This study addresses the limitations of past research, focusing on a real campus's enclosed high-rise student apartment courtyard. Using three key design variables (courtyard area, building height and ground-level interface transparency), 27 sample scenarios were developed for psychological experiments. The findings indicate that while visual scene complexity has minimal impact on oppression to confined environments, building exposure and sky visibility do. People's perception of openness is determined by building exposure, sky visibility, and visual complexity. Higher visual complexity and greater sky visibility enhance the sense of openness. Satisfaction is primarily influenced by sky visibility. The study also conducts a multiple linear regression of spatial and psychological indicators and discusses the tolerance threshold for spatial oppressiveness and the spatial oppressiveness under various spatial types of samples.

Quantifying the spatial quality of urban streets with open street view images: A case study of the main urban area of Fuzhou

With the advancement of global urbanization, urban streetscapes have become a critical part of urban public spaces. As one of the important ways to enhance the living environment, relevant government departments have accelerated the construction of urban streetscapes; however, certain issues, such as emphasis on surface and light protection, still persist. The visual effects of street landscapes hardly meet people's daily and spiritual needs. Therefore, assessing the quality of urban streetscapes has scientific and practical significance for improving urban planning and construction and creating a new intelligent and green city. In this study, the spatial distribution of vehicle interference index, spatial feasibility index, road area index, green visual index, sky visibility index, spatial enclosure index, color richness index, and visual entropy evaluation indices were drawn from the framework of combining deep learning and machine learning to quantify the spatial quality of urban streets by integrating a large number of streetscape images. The spatial quality of street landscape was evaluated according to the ELO scoring mechanism and random forest method, taking the main urban area of Fuzhou City as an example. The results showed that the overall street landscape quality of Fuzhou City was high, and the spatial distribution showed a pattern of concentrated high values in the center and dispersed high values in the periphery. Therefore, based on quantifying the spatial quality of urban streets, strategies, such as the pavement layout of pedestrian and vehicular paths, control of the continuity and permeability of visual landscape elements, and plant color matching, should be regulated. The method proposed in this study can provide novel insights for urban builders to improve the construction of cities.

Effects of Audio-Visual Environmental Factors on Emotion Perception of Campus Walking Spaces in Northeastern China

In the context of urban sustainable development and the creation of pedestrian-friendly campus environments, optimizing campus walking spaces has emerged as a central focus in urban planning research. Presently, research in pedestrian environments predominantly adopts a macroscopic perspective, offering limited insights into pedestrians’ subjective experiences and emotional perceptions at a micro level. Therefore, this study conducted on-site experiments in 21 walking spaces across three campuses, utilizing image semantic analysis, multifunctional sound level meter, wearable electrocardiography devices, and the Profile of Mood States (POMS) to collect data separately on audio-visual environmental factors and pedestrians’ emotional states. This study’s findings revealed significant correlations (p < 0.01) among factors such as the Green Visual Index, Spatial Enclosure Index, Sky Visibility Index, Spatial feasibility Index, and Equivalent Continuous A-weighted Sound Pressure Level with physiological and psychological alterations in pedestrians’ emotions. Additionally, the various proportions of audio-visual environmental factors also exerted significant influences on emotions (p < 0.05). The relevant conclusions can provide a reference for optimizing the audio-visual environment of walking space and promoting the sustainable development of the campus. In future research, the effects of audio-visual environments on both emotional and physiological indicators, as well as subjective evaluations, can be explored further.

Establishing a link between complex courtyard spaces and thermal comfort: A major advancement in evidence-based design

Amidst climate change, the importance of climate-adaptive design in architecture and landscape design has surged, particularly in residential courtyards, where optimizing the microclimate is paramount to residents' well-being. Traditional spatial indices, however, fall short in accurately characterizing complex courtyards and local spatial features. To overcome these limitations, this study introduces pixel-level spatial indicators that effectively overcome these constraints. These indicators are implemented using computational geometry algorithms such as Ray Tracing, Flood Fill, and A*, enabling simulation of various courtyard spatial indicator maps. We also utilize Graphics Processing Unit (GPU)-based rapid thermal comfort simulation technology to generate thermal comfort maps. By applying data mining methods such as Partial Least Squares Regression (PLSR), Pearson correlation, and Nearest-neighbor interpolation, we explore the relationships between spatial indicators and thermal comfort, ultimately identifying key indicators and determining the guiding thresholds and influencing trends corresponding to heat discomfort frequency. Six key indicators and th emerge: Building View Factor (BVF), indicating building coverage visibility (prefer above 0.11); Solar Beam Fraction (BEAM), illustrating Summer solstice sun shading condition (prefer below 0.78); Averaged View Factor (AVF), showing overall visibility (prefer below 0.40); Directional Sky View Factor (DSVF(W)), reflecting sky visibility in a specific orientation (prefer below 0.73); Tree View Factor (TVF), denoting tree coverage visibility (prefer above 0.18); and Plan Water Ratio (PWR), signifying water surface proportion (aim for below 0.44). These insights, integrated into design tools, contribute to evidence-based microclimate regulation strategies, thereby enhancing urban residents' thermal comfort and overall well-being.

Effect of the Visual Landscape and Soundscape Factors on Attention Restoration in the Public Space of Old Residential Areas by VR

The purpose of this study is to analyze the relationship between the visual landscape and soundscape factors of the public spaces in old residential areas and their attention restoration benefits for residents and to determine the main influencing factors. In this paper, the public spaces of six typical old residential areas in Tianjin were selected as the research object, and the restorative benefits of the respondents were analyzed through virtual reality environment, subjective evaluation, and attention testing methods. The results showed that the attention restoration benefits of the central square in the old residential area were better than those of the public space along the street. Second, greenery satisfaction, environmental cleanliness, architectural aesthetics, sky visibility, and soundscape evaluation are all significantly positively correlated with the attention restoration level. Finally, a "visual landscape and soundscape perception evaluation-attention restoration level" structural equation model was constructed. According to the model, both the visual landscape factors and soundscape evaluation factors in old residential areas had a direct positive impact on the attention restoration level, with a greater impact exerted by visual landscape factors than by soundscape evaluation factors. The findings from this study can provide significant information for the renewal of old residential areas.

Effects of local trees on the environmental climate of urban outdoor spaces in arid and semi-arid regions

The purpose of this study is to assess actual and potential environmental aspects related to the impact of local tree areas on local climate control and to assess external thermal comfort. This has allowed us to assess its sustainability in the light of achievable environmental benefits. Sustainability can be defined as the property of a material or product that indicates how well it meets current requirements for a particular application. These demands affect the well-being and health of city dwellers. We approach this study with an ecological approach, focusing on the effects of native trees (palms and olive trees) and exotic trees (Ficus letesa). Adjust the microclimate of the city. The study highlights the positive effects of plants on urban outdoor spaces in the city of Biskra during July and August, the hottest months of the year when temperatures can reach values above 50 degrees Celsius. I made it A green strategy is an essential element in improving the external local climate, especially in dry climates. The main criteria we relied on in this study included vegetation density, tree placement and orientation, and country albedo. Based on these three criteria, we have achieved very important results in terms of improving and adjusting the urban microclimate.- Selection of the components of the regional urban forest model that have the greatest impact on regional climate and cooling effects. In addition to these factors, the impact of urban forests on local climate also emphasizes permeability, tree abundance, sky visibility, leaf area index, and distance between trees.-Urban green spaces, especially olive and palm trees, have a positive impact on the outdoor microclimate, reduce the urban heat island effect in the summer in the shade of tall trees and shrubs, attenuate solar radiation, Being able to block the flow of heat from the sky, thereby increasing the comfort of the microclimate and change. In addition, evaporation and transpiration from plants reduce temperature and increase humidity.

Interference of Meteorological Variables on Night Sky Observation in Rural and Urban Zones of South-Western Spain

Several factors affect the visibility of the night sky, most significantly artificial light at night (ALAN), meteorological conditions and Moon illumination. There are few studies that analyse the effect of meteorological conditions and Moon illumination, especially in rural areas (where the ALAN level is lower). An analysis of these variables could be relevant for sky observation, especially for astronomical observatories, usually located in rural areas with low ALAN. Knowledge of the relevant variables in the observation allows for the correct planning of the observation. The observer can consult meteorological agencies for forecasts of these variables, allowing him to know in advance whether the observation will be carried out under optimal conditions. In this study, a photometer and a weather station were installed in various municipalities located in rural areas of south-western Spain. This equipment was also installed in the city of Badajoz (urban area with high ALAN). These devices carried out simultaneous measurements of night sky darkness (NSB) and meteorological conditions for a period of approximately 6 months. A statistical analysis of the recorded data was carried out. Only the Moon illumination was slightly correlated with NSB in both cases (−0.3 in rural areas and −0.35 in urban areas). Sky temperature only proved a correlation with NSB in the urban area (−0.41). The correlations indicated are significant at the 0.01 level. The results obtained in the urban area were confirmed by a second analysis using meteorological data provided by a meteorological agency, obtaining similar results. A web application was developed that allows for real-time consultation of NSB and meteorological data for each area, which can help observe the starry sky. Globally, the results obtained in this study could help in the planning of stargazing in both urban and rural areas, allowing one to know in advance if weather conditions would affect the perception capacity.

Actual sky visibility under shading by trees with different crown densities

Introduction. The development of green infrastructure is an important task in urban planning strategies to reduce urban heat island effect and improve urban ecosystem. The aim of this study is to determine the actual visibility of the skyline when shaded by trees of different crown densities. The scientific novelty is that for the first time a study of the actual sky visibility with trees shading as complex heterogeneous systems has been conducted to assess the effect of mitigating of urban heat island. The practical significance lies in the establishment of the actual visibility of the firmament under the shading of trees with different crown density, which enables the correction of simulation models to analyze the parameters of the microclimate of the urban environment under given climatic conditions.
 
 Materials and methods. Various approaches to determining the sky visibility are considered. Direct measurements were made by photographing with a special fisheye lens and a smartphone. The research was carried out in a temperate continental climate (according to the international climate classification Köppen — type Dfa). Several tree species most commonly found in landscaping under the climate conditions in question and having different crown densities were selected: elm, oak, maple and poplar. For each, several samples were selected as required for data averaging. A total of 27 samples were studied.
 
 Results. A diagram of measured averaged values of the sky visibility factor was plotted, taking into account shading by trees with different crown densities in different periods of the year. To protect trees with dense spreading crowns from the direct solar radiation in the summer daytime, it is better to use trees with dense spreading crowns to intensify the radiant heat exchange of the urban surface with the sky at night — trees with less dense crowns. In case of the need to soften the urban heat island during the day, hybrid solutions are the most effective.
 
 Conclusions. The actual assessment of the sky visibility, made by the authors taking into account shading by trees, allows us to make corrections in simulation models to analyze the parameters of the microclimate of the urban environment under the given climatic conditions. The results of the study make it possible to select the type of tree providing the required shading and urban heat island’s mitigation effect.

Green Is Not the Same as Green: Differentiating Between the Association of Trees and Open Green Spaces With Children’s Brain Structure in the Netherlands

There is accumulating evidence for positive effects of green spaces on mental and brain health. Here we investigated whether differentiating the types of green spaces may be relevant. On longitudinal data of children ( N = 95) from the Netherlands, we quantified the link between green space exposure at home from birth onwards and MRI brain structure at 12.5 years. We differentiated between green space resulting from trees versus open green spaces and also associated visibility of sky (sky view factor) with brain structure (200 m buffer around home address). We observed a positive association between grey matter volume in different prefrontal clusters and green open space coverage as well as sky view, but a negative association within prefrontal clusters for tree cover density. Most importantly, in the medial prefrontal cortex, the only region in which all three analyses overlapped, the visibility of sky was the most important predictor. Our findings advance knowledge on health-promoting, evidence-based urban planning.

Study on Camping Behavior Patterns for Thermal Comfort at Riverside Parks

People-oriented landscape experiences have become the focus of park design with the increasing demand of outdoor activities from urban residents, whereas thermal-comfort-guided landscape design has attracted more attention in academic circles. Based on the investigation of the microclimate of typical subregions in riverside parks, this paper uses AI recognition to analyze the spatiotemporal distribution of camping crowds, and considers the correlation between landscape morphological parameters, microclimates, and crowd behavior. Finally, we built a model to raise the number of landscape optimization strategies for landscape design. The results show that landscape morphological parameters, such as tree height, crown canopy, and sky visibility factor (SVF), can significantly affect the air temperature (Ta), relative humidity (RH), and physiological temperature (PET) in an environment, while hardly affecting wind speed (WS). For microclimate parameters, Ta has a moderate correlation with camping behavior, with a correlation coefficient of −0.145 and a p-value of 0.040, while the corresponding correlation with PET was non-significant with a p-value of 0.622. The temporal distribution of the number of campers per day show a linear upward trend with a reasonable goodness-of-fit, with an adjusted R2 above 0.789 for all subregions. The model based on landscape morphological parameters has a good fit, with coefficients of tree height and crown canopy of −0.195 and 1.316, respectively. This study provides theoretical support and design suggestions for the design of riverside parks based on crowd behavior patterns.

The effects of audio-visual perceptual characteristics on environmental health of pedestrian streets with traffic noise: A case study in Dalian, China.

The COVID-19 pandemic has affected city dwellers' physical and mental health and has raised concerns about the health of urban public spaces. This field investigation research in Dalian, China, examined the perceived audio-visual environment characteristics of urban pedestrian streets with traffic noise and their influences on the environmental health of the pedestrian streets. Five indicators reflecting psychological responses to environmental characteristics (willingness to walk, relaxation, safety, beauty, and comprehensive comfort) were used to measure environmental health of pedestrian streets with traffic noise. The results showed that safety was rated the highest, and willingness to walk was evaluated as the lowest among health evaluation indicators. The imageability and openness of the streetscape were associated with each health evaluation indicator. In contrast, the rhythm and continuity of the street buildings had a greater effect on willingness to walk than the other health indicators. There were negative correlations between L Aeq for traffic noise and health evaluations. Positive health evaluations were observed when L Aeq was less than 55 dBA. In contrast, soundscape indicators showed positive correlations with health evaluations, and acoustic comfort and noise annoyance, rather than sound preference and subjective loudness were associated with each health evaluation indicator. In terms of the combined audio-visual factors, acoustic comfort, the quantity of greening, annoyance, sky visibility, spatial scale, and building distance were examined as the determining factors affecting health evaluations, and 55.40% of the variance in health evaluations was explained by the soundscape and streetscape indicators. The findings provide references for better understanding the relationships between healthy experience and audio-visual perceptions. Moreover, they enable environmental health quality optimisation of pedestrian spaces considering audio-visual indicators and approaches in the post-epidemic era.

The Impact of Campus Outdoor Space Features on Students’ Emotions Based on the Emotion Map

To explore the influence of campus public space characteristics on students' emotions, we investigated the association mechanism between public space characteristics and students' emotions concerning the distribution of students' emotions in public spaces. The present study used photographs of facial expressions taken over two consecutive weeks as a source of data regarding the students' affective reactions. The collected facial expression images were analyzed using facial expression recognition. Values were assigned to the expression data, combined with geographic coordinates to create an emotion map of the campus public space using GIS software. Then, spatial feature data via emotion marker points were collected. We used smart wearable devices to combine the ECG data with spatial characteristics and took SDNN and RMSSD as ECG indicators to assess mood changes. We analyzed the correlation between these spatial features and heart rate variability and developed regression models for the ECG data. The findings show that sky visibility, space D/H, green visibility, skyline change index, and boundary permeability can engage students' positive emotions in a meaningful way. On the other hand, paving visibility and road linearity tends to induce negative emotions in students' minds.

Urban landscape and climate affect residents’ sentiments based on big data

Residents’ sentiments are a quantitative indicator of human feelings, which is useful for optimizing urban residential environments. Little is known about the spatiotemporal variations and potential drivers of sentiment based on big data. A total of 221,104 Weibo social media data were used to quantify daily sentiment in the Beijing metropolitan area during the COVID-19 pandemic from January 1, 2021 to March 8, 2022. Deep-learning natural language processing was used to extract this dataset to investigate the spatiotemporal sentiment patterns. The density of roads and buildings, normalized difference vegetation index (NDVI), population, sky visibility factor, daily land surface temperature (LST), daily precipitation, and daily air pollution concentrations (CO, NO2, PM2.5, SO2, and O3) were explored as potential drivers of sentiment. Results show that (1) the holiday sentiment was 1.31% higher than on weekends and 4.61% higher than on weekdays. Extreme precipitation, air pollution, and COVID-19 lockdown measures have reduced sentiment. (2) The sentiment in spring was found to be the highest. The numbers of functional zones with high sentiment values (>0.8) in spring were 13.59%, in summer 34.48%, and in autumn 14.71%. (3) Sentiment was highest under conditions of moderate greenness (0.4<NDVI<0.6) and comfortable daily temperature (25 °C < LST<30 °C). (4) Sentiment was negatively associated with daily air pollutants, such as PM2.5, NO2, and CO. This paper presents the effectiveness of sentiment quantification based on social media data and deep-learning techniques. The results provide practical implications and support decisions for sustainable urban health development.

COMBINED EFFECTS OF PHYSICAL ENVIRONMENT ELEMENTS ON THE PERCEPTION AND COMFORT OF URBAN PUBLIC OPEN SPACE USERS: A UNIVERSITY CAMPUS CASE

Aim: This study examines the effects of urban public spaces, which have physical environmental elements (heat, light, sound, etc.) that vary according to seasons and time of day, on the environmental assessments and quality of life of city residents. Objectively and subjectively investigating the combined effects of such multiple physical environmental elements on people's environmental perception and thermal, auditory, visual and general comfort can make significant contributions to the design and application fields. Method: The study is based on a field study conducted in two open areas with different physical environmental elements on a university campus in Eskişehir. In this context, the difference between objective parameters of various physical environmental elements on the campus (temperature, humidity, sound pressure level, brightness level, etc.) and subjective evaluations obtained from surveys about users' perception and comfort of the physical environment (thermal, auditory, visual and general comfort evaluations). The relationship was examined with statistical analysis. Results: Research results show that horizontal-vertical brightness level, temperature, relative humidity and sky visibility have a significant effect on general comfort. However, the effect and type of effect of sound pressure level and wind speed on general comfort have not been determined. Conclusion: As design input, overhead cover elements and mobile seating units are recommended as improvement strategies that can be developed to increase the general comfort level of campus open spaces. This study can provide valuable guidance in the design and management of urban public spaces.

Selection of Areas for Effective GNSS Spoofing Attacks to a Vehicle-mounted MSF System based on Scenario Classification Models

The inherent vulnerability of the Global Navigation Satellite System (GNSS) leads to the ease of implementation of spoofing attacks. The latest GNSS spoofing attack schemes still suffer from low success rate, long attack time, and poor concealment. To improve the success rate, an efficient GNSS spoofing attack method for a vehicle-mounted Multi Sensors Fusion (MSF) system is proposed based on the scenario classification models with a spatial database. Firstly, the influence of the two typical urban scenarios, which are 1) the road with buildings on both sides and 2) tunnels, on the GNSS spoofing attack is analyzed. Then a dynamic Bayesian network model considering the sky visibility generated with the 3D building models and tunnel models inside the spatial database is established to quantify the difficulty of the attack. Furthermore, the scenarios of the victim can be classified into high-risk and low-risk scenarios. When the vehicle is just out of the tunnel or in open scenarios, attackers can select these high-risk scenarios and implement aggressive spoofing attacks. Then the efficiency of the GNSS spoofing attack can be significantly improved. Finally, the proposed attack scheme is demonstrated by actual world data with simulated spoofing attacks in urban areas.