Sky View Factor

Surface radiation data were collected at seven sites in the Riviera Valley in southern Switzerland during the special observing period of the Mesoscale Alpine Programme's Riviera project from August until October 1999. During the daytime on selected 'valley wind' days, strong site contrasts occurred with respect to solar and downward long-wave radiation fluxes. Site-to-site differences of incoming global radiation were caused by the different orientations of valley surfaces relative to the direct solar beam component and by shading from surrounding topography. Diurnal cycles of albedo, determined from horizontal and slope-parallel measurements of reflected and incoming global radiation at three eastern side-wall sites, show that reflection of the direct radiation component from the inclined surfaces is predominantly anisotropic diffuse radiation. Downward longwave radiation decreases with elevation in the valley because the higher sites have an increased angular exposure to the radiating sky (i.e. sky view factor). Contrasts between the valley-floor and ridge-top sites are largest on valley wind days but also occur on overcast days. Finally,strong site-to-site variations of the net all-wave radiation occur during daytime due to variations in the received direct beam component of incoming global radiation. During night-time, net outgoing all-wave radiation increases with elevation, again because sky view fraction increases with elevation. On valley wind days, significant contrasts are found in mean diurnal cycles and daily sums of available radiation energy between south-west and north-east facing slopes. When the direct beam component is absent, inter-site contrasts in radiation components are reduced, especially short-wave radiation components. A simple semi-empirical method is described to estimate the net all-wave radiation in a slope-parallel frame of reference from measurements with horizontally exposed net radiometers. This method employs the theoretical ratio of short-wave radiation on a slope to the horizontal equivalent. The method is tested successfully at one site where simultaneous measurements were made with inclined and horizontal sensors.

ABSTRACT: This paper addresses urban microclimates as a function of urban design in central Sao Paulo, Brazil. Sao Paulo is now the second largest city in the world with a population of nearly 19 million in its metropolitan area. It has a tropical, albeit polluted climate and is subject to ...

Sky view factor (��sky) is used in radiation balance schemes for the partitioning of longwave and shortwave radiation within urban and forest canopies and complex terrain. In the urban environment, ��sky and 1-��sky give a measure of how much radiation will penetrate the canopy and how much will be intercepted by the canopy, respectively. As part of the Oct. 2000 URBAN Field Experiment in Salt Lake City (Shinn et al., 2001), photographs were taken in the downtown area at ground level shooting upwards using a fisheye lens. ...

Sky view factor (SVF) is a well-known parameter in urban-climatic studies, but there is a lack of consensus on its effectiveness, especially with regard to the interpretation of changes in urban air temperatures. This led the authors to develop the new concept of the partial sky view factor (SVFp), which showed promise in a previous study. The objective of this study is to save the time associated with manual methods of calculating SVF and SVFp by developing a Rhino-Grasshopper component to quantify them via the hemispheric projection of a 3D model. In addition, a different approach, in terms of a hemispheric projection to calculate SVF, will be introduced by another component, and the pros and cons of each approach are considered. We will name these methods`Ray Method' and`Geometrical Method' respectively. The Ray Method has achieved a good balance between accuracy, processing time and urban scale and complexity compared to the Geometrical Method.

Shading affects outdoor thermal environments and, therefore, influences the thermal perceptions of people in outdoor spaces. Since most field studies examining outdoor thermal comfort merely elucidated characteristics measured on a particular day, these studies may not represent ...

This paper presents the results of the first attempt to assess, identify and quantify the residual number of shell craters of World War I currently present in the Vezzena/ Luserna/ Lavarone Plateau, areas of Millegrobbe, Bisele and Cima Campo (TN, Italy). Historical sources report the existence of several thousand of artillery explosions: therefore, a field survey or a classic photointerpretation appeared as labor-intensive and highly time-consuming. For this reason, a Digital Terrain Model (DTM) of the test-site was processed using the Sky-View Factor algorithm and was analyzed with an object-based approach, which implied: 1) multi-resolution segmentation; 2) classification (main features considered size, shape and color).
The automatically classified shell craters were thus verified during an in situ survey that determined the accuracy of the method in the order of 84% of the total occurrences.

For example, thermal indices that are derived from the energy balance of the human body can be of great use for tourism. Standard climate data, such as air temperature, air humidity and wind speed are required in order to calculate and quantify the thermal bioclimatic conditions. ...

This research seeks to determine the relationship between the thermal environment and “sky view factor”. This study was conducted in Iran, Tehran, in five parks area. Photographs were taken in the urban parks' area at ground level shooting upwards using a fisheye lens. Utilizing image analysis and in processing software, “Sky view factor” was computed for each photograph.

The urban environment has been dramatically changed by artificial constructions. How the modified urban geometry affects the urban climate and therefore human thermal comfort has become a primary concern for urban planners. The present study takes a simulation approach to analyze the influence of urban geometry on the urban climate and maps this climatic understanding from a quantitative perspective. A geographical building database is used to characterize two widely discussed aspects: urban heat island effect (UHI) and wind dynamics. The parameters of the sky view factor (SVF) and the frontal area density (FAD) are simulated using ArcGIS-embedded computer programs to link urban geometry with the UHI and wind dynamic conditions. The simulated results are synergized and classified to evaluate different urban climatic conditions based on thermal comfort consideration. A climatic map is then generated implementing the classification. The climatic map shows reasonable agreement with the...

Many urban studies have been done to demonstrate that urban sprawl is not the right approach in hot climate cities. On the contrary, a compact design is recommended to enhance human thermal comfort. This research aims to clarify the relation between urban morphology and outdoor thermal comfort of Jeddah, Saudi Arabia. The aim is to develop an outstanding future strategic compact morphology that would facilitate a dynamic development of the city. Jeddah city will soon have a subway that is expected to radically change the habits of its inhabitants. Our idea is to consider the main stations of the future metro as nodes, creating more densely inhabited localities and also defining transitional spaces for pedestrian activities. Microclimates generated in and around these activity nodes must be particularly studied to encourage residents and visitors to reclaim a pedestrian life that was clearly noticeable in the old city, but has virtually disappeared in most recent neighborhoods, entirely devoted to automobile transport. Services and facilities around metro nodes should become the transitional thermal comfort areas of the metro station exits. This paper will provide numerical modeling simulations that are used to assess the solar radiation in the urban layout (the old compact area and the modern sprawl area) by the software "Heliodon 2" (direct shortwave, Sky View Factor) and "Heliodon plus" (climatic data) to clarify the differences between the old and the new layout and why the change to compactness needs to be put into effect.

View factors for sky, trees, and buildings are three important parameters of the urban outdoor environment that describe the geometrical relationship between different surfaces from the perspective of radiative energy transfer. This study develops an approach for accurately estimating sky view factor (SVF), tree view factor (TVF), and building view factor (BVF) of street canyons in the high-density urban environment of Hong Kong using publicly available Google Street View (GSV) images and a deep-learning algorithm for extraction of street features (sky, trees, and buildings). As a result, SVF, TVF, and BVF maps of street canyons are generated. Verification using reference data of hemispheric photography from field surveys in compact high-rise and low-rise areas shows that the GSV-based VF estimates have a satisfying agreement with the reference data (all with R 2 > 0.95), suggesting the effectiveness and high accuracy of the developed method. This is the first reported use of hemispheric photography for direct verification in a GSV-based streetscape study. Furthermore, a comparison between GSV-based and 3D-GIS-based SVFs shows that the two SVF estimates are significantly correlated (R 2 = 0.40, p < 0.01) and show better agreement in high-density areas. However, the latter overestimates SVF by 0.11 on average, and the differences between them are significantly correlated with street trees (R 2 = 0.53): the more street trees, the larger the difference. This suggests that a lack of street trees in a 3D-GIS model of street environments is the dominant factor contributing to the large discrepancies between the two datasets.

The design of a future building with very high energy efficiency demands from the architect to study the available solar resources in this urban environment. The purpose of the presented methodology is to study the variations in all components of the incident solar radiation daily, monthly and seasonally for all building facades.  This is realized in the computer program 3D–SOLARIA. In the focus of the paper is the estimation of the background component of the incident diffuse solar irradiation on a building facade under orthogonally obstructed sky, using anisotropic sky view factors.

Many urban studies have been done to demonstrate that urban sprawl is not the right approach in hot climate cities. On the contrary, a compact design is recommended to enhance human thermal comfort. This research aims to clarify the relation between urban morphology and outdoor thermal comfort of Jeddah, Saudi Arabia. The aim is to develop an outstanding future strategic compact morphology that would facilitate a dynamic development of the city. Jeddah city will soon have a subway that is expected to radically change the habits of its inhabitants. Our idea is to consider the main stations of the future metro as nodes, creating more densely inhabited localities and also defining transitional spaces for pedestrian activities. Microclimates generated in and around these activity nodes must be particularly studied to encourage residents and visitors to reclaim a pedestrian life that was clearly noticeable in the old city, but has virtually disappeared in most recent neighborhoods, entir...

City streets are a focal point of human activity in urban centers. Citizens interact with the urban environment through its streetscape and it is imperative to, not only map city streetscapes, but quantify those interactions in terms of human well-being. Researchers now have access to fully digitized representation of streetscapes through Google Street View (GSV), which captures the profile view of streetscapes and, thus, shares equivalent viewing angles with those of the citizen. These two facets – a wealth of streetscape photographs at city-scale and a shared perspective with the end user – underscore the potential of these data in street-level urban landscape mapping. In this study, we introduce two examples that demonstrate GSV as a high-quality data source for mapping street greenery and openness. First, the modified green view index, which estimates the visibility of street greenery, was applied to static GSV images in order to map the spatial distribution of street greenery. Second, GSV panoramas were used to quantify and map the openness of street canyons by applying a geometrical transformation and image classification to the panoramas. The results of these two novel applications of street-level photographic data illustrate its utility for quantifying and mapping key urban environmental features at the same viewpoint in which we, as citizens, experience the urban landscape.

City streets are a focal point of human activity in urban centers. Citizens interact with the urban environment through its streetscape and it is imperative to, not only map city streetscapes, but quantify those interactions in terms of human well-being. Researchers now have access to fully digitized representation of streetscapes through Google Street View (GSV), which captures the profile view of streetscapes and, thus, shares equivalent viewing angles with those of the citizen. These two facets – a wealth of streetscape photographs at city-scale and a shared perspective with the end user – underscore the potential of these data in street-level urban landscape mapping. In this study, we introduce two examples that demonstrate GSV as a high-quality data source for mapping street greenery and openness. First, the modified green view index, which estimates the visibility of street greenery, was applied to static GSV images in order to map the spatial distribution of street greenery. Second, GSV panoramas were used to quantify and map the openness of street canyons by applying a geometrical transformation and image classification to the panoramas. The results of these two novel applications of street-level photographic data illustrate its utility for quantifying and mapping key urban environmental features at the same viewpoint in which we, as citizens, experience the urban landscape.

همگام با الگوبرداری از شیوه‌های مدرن و رویکردهای جدید ساخت‌وساز در حوزه‌های معماری و معماری منظر، تجارب سنتی موجود بر پایۀ بهره‌گرفتن از انرژی‌های طبیعت، تقریباً به فراموشی سپرده ‌شده است. در این باره، هنر باغ‌سازی ایران، ارزش‌ها و دستاوردهای ارزشمندی دارد که نیازمند مطالعه و بازشناسی است. شهر شیراز به‌واسطۀ جغرافیای خاص خود، به‌تنهایی دارای تعداد زیادی از باغ‌هایی با شهرت جهانی نظیر باغ ارم، باغ تخت، باغ جهان‌نما و باغ دلگشاست. هدف اصلی این مقاله بررسی ویژگی‌های ساختاری و به‌ویژه نقش سایه در بهبود شرایط آسایش اقلیمی باغ‌ها به‌عنوان بخش مهمی از فضاهای باز و سبز شهرها و منظر شهری است. در این باره، از دیدگاه معماریِ منظر با تکیه بر دو نمونۀ بارز باغ‌ ایرانی همچون جهان‌نما و دلگشا، برای اولین بار پژوهشی کمّی ‌ـ کیفی برای سنجش وضعیت گرمایی خرداقلیم باغ در مقایسه با اقلیم محلی و فضای شهری پیرامون، در اوج گرمای تابستان و اوج سرمای زمستان صورت گرفت. در چارچوب روش کار نیز از جدیدترین شاخص ارزیابی وضعیت گرمایی فضای باز با عنوان شاخص جهانی اقلیم گرمایی (UTCI) برای ارزیابی داده‌های برداشت‌شده در روزهای چهار و پنج بهمن ماه 1391 و نه و سیزده مرداد ۱۳۹۲ استفاده شده است. داده‌های میدانی نیز بر روی شبکه‌ای ازپیش‌تعیین‌شده در سطح باغ، توسط دستگاه‌های هواشناسی سیار که قادر به برداشت آمار دما، رطوبت، باد، فشار هوا و دمای تابشی است، گردآوری شده است. نتایج نهایی حاصل از مقایسۀ آمار استخراج‌شده از ایستگاه‌های هواشناسی و داده‌های برداشت‌شده، نشان داد که ویژگی‌های ساختاری و کالبدی نمونه‌های مطالعاتی تا چه میزان، وضعیت اقلیم خرد را نسبت به اقلیم محلی، اقلیم کوتاه‌مدت و اقلیم بلندمدت شهر تعدیل کرده است. بنابراین، تعیین نقش و توان باغ ایرانی در بهبود کیفیت اقلیم خرد و اقلیم محلی در کنار بررسی نقش مجموعه عناصر شکل‌دهندۀ این باغ‌ها در بهبود شرایط آسایش اقلیمی درون، مهم‌ترین محصول پژوهش تلقی شده است.

Urban Planning has an immense impact on local microclimate which in turn affects the comfort and space quality within a city. The urban open spaces play an important role in creating the urban climate. The urban streets vary in geometry as defined by height/width ratio, sky view factor (SVF) and the orientation that is defined by its long axis. This directly influences the absorption and emission of incoming solar and outgoing long wave radiation which has a significant impact on the temperature variations within the street as well as the surrounding environment (Urban Heat Island).

While aspen (Populus tremuloides Michx.) cover provides protection from growing season radiative frosts, reduced light levels can limit growth of understory white spruce (Picea glauca (Moench) Voss). The creation of openings around individual spruce can provide more light, but the chance of radiative frost damage increases as gaps become larger. We examined the relationship between opening size and light and

Most of Naples Historic District is an example of “introverted” urban fabric due to the noteworthy
presence of inner courtyards. They represent a concealed heritage to be preserved and endorsed,
through the reconnection to socio-economic mechanisms of the city. The re-thinking of those places in a
collective sense is an important opportunity for such a dense fabric as that of Naples, characterized by a
remarkable public spaces shortage. In fact, the regeneration of the heart of the city can have the double
meaning of both looking for further urban resources and restoring a collective identity in a functional
and sustainable perspective. By means of an analytical approach, we have produced a methodology
aimed at enhancing courtyards’ potentialities and their socio-environmental assets, starting from morphological
characteristics of urban fabrics. This paper provides early findings of such study, through a
project proposal, which confers on courtyards a new connective role in urban texture.