Ground Coverage Ratio Research Articles

The Effect of Ground Coverage Ratio on Daytime Land Surface Temperature - Focusing on the Residential Area of Seoul

The Effect of Ground Coverage Ratio on Daytime Land Surface Temperature - Focusing on the Residential Area of Seoul

Large-eddy simulations of ventilation for thermal comfort — A parametric study of generic urban configurations with perpendicular approaching winds

This study investigates ventilation performance in parametric urban scenarios using a large-eddy simulation (LES) model called the Parallelized LES Model (PALM). With various combinations of planning parameters, air flows and pedestrian-level velocity ratios in a total of 48 scenarios are investigated. Major findings and recommendations are: First, ground coverage ratio (λp) is the most important factor for good ventilation. Second, in cases of homogeneous building heights, a power regression between velocity ratios and aspect ratios of parallel street canyons can be derived, which suggests that good understanding of local microclimate, especially prevailing wind directions in summer, is needed in urban planning. Third, the effects of building height differentials on urban ventilation are connected to urban density. In low-density scenarios, inhomogeneous building heights give worse ventilation performance compared to homogeneous cases. In high-density scenarios, inhomogeneous building heights result in better ventilation performance than homogeneous cases. Inhomogeneous building heights generate more vertical momentum fluxes in street canyons and have a negative (positive) effect on velocity ratios of low-density (high-density) parametric urban fabrics. The application of this point is that homogeneous building heights are recommended when low density is present, and inhomogeneous building heights may be better in cases of high density.

EasyPCC: Benchmark Datasets and Tools for High-Throughput Measurement of the Plant Canopy Coverage Ratio under Field Conditions.

Understanding interactions of genotype, environment, and management under field conditions is vital for selecting new cultivars and farming systems. Image analysis is considered a robust technique in high-throughput phenotyping with non-destructive sampling. However, analysis of digital field-derived images remains challenging because of the variety of light intensities, growth environments, and developmental stages. The plant canopy coverage (PCC) ratio is an important index of crop growth and development. Here, we present a tool, EasyPCC, for effective and accurate evaluation of the ground coverage ratio from a large number of images under variable field conditions. The core algorithm of EasyPCC is based on a pixel-based segmentation method using a decision-tree-based segmentation model (DTSM). EasyPCC was developed under the MATLAB® and R languages; thus, it could be implemented in high-performance computing to handle large numbers of images following just a single model training process. This study used an experimental set of images from a paddy field to demonstrate EasyPCC, and to show the accuracy improvement possible by adjusting key points (e.g., outlier deletion and model retraining). The accuracy (R2 = 0.99) of the calculated coverage ratio was validated against a corresponding benchmark dataset. The EasyPCC source code is released under GPL license with benchmark datasets of several different crop types for algorithm development and for evaluating ground coverage ratios.

Optimal solar dish field layouts for maximum collection and shading efficiencies

We derive the limit for collection and shading efficiencies and describe an optimization methodology of solar dish field layouts based on a general 2D Bravais lattice using local irradiation data and as a function of latitude, ground coverage ratio, dish perimeter shape, and sun-tracking system.

Exploring the relationships of between land surface temperature, ground coverage ratio and building volume density in an urbanized environment

Abstract. The objective of this study is to explore and compare the relationships between urban land surface temperature (LST), ground coverage ratio (GCR) and building volume density (BVD). Landsat ETM+ data of August 2011 and August 2013 are used to estimate the LST for Wuhan, China, metropolitan area, and maps of GCR and BVD are generated using building census data of 2011 and 2013. Our analysis indicates there is a strong linear relationship between LST and GCR, and when GCR is lower, the linear correlation is more prominent, whereas the relationship between LST and BVD is not straightforward, but seems some underlying pattern. The result suggests GCR and BVD provide complementary metrics to the traditionally applied land use/land cover (LULC) for analysing LST quantitatively for surface urban heat island studies using thermal infrared remote sensing in an urbanized environment. This study is of positive significance to understand today’s urban heat island issues, and contributes to the planning work of urban architectural space.

Coevolution of urban form and built form: a new typomorphological model for Tehran

The paper brings analytical and typological models to the study of the coevolution of urban form and built form in Tehran. It follows the transformation of housing at both urban and architectural scales. At the urban scale, residential areas in Tehran have evolved from small irregular blocks to larger regular grids. At the architectural scale, residential units have evolved from courtyard houses, to terraced houses with south-facing courts, to multistorey apartment units. How do these two processes of evolution relate to each other? Are they entangled in a coevolutionary pattern, or do they remain independent evolutionary developments circumstantially brought together? The paper answers this question by looking at a series of stereotypical built forms for housing in Tehran over time, and by developing a model that brings together parameters of urban structure including block and plot size, and ground coverage ratio, with parameters of built form including access frontage, day-lit depth, and plan shape. In order to build the model and quantify its parameters, three areas of Tehran, representative of its three key stages of growth, are analysed using GIS. The model is found to be capable of approximating reality. During a process of design experiments with blocks of the same dimensions, it is found that alternative built forms are possible, all conforming to similar ratios of ground coverage, floor space index, day lighting, and road access.

Modeling of a concentrating photovoltaic system for optimum land use

ABSTRACTConcentrating photovoltaic solar power plants using dual‐axis trackers are in increasing demand. In a utility‐scale photovoltaic system, both capacity factor and ground coverage ratio are widely used to characterize systems in view of the land use efficiency. Current system modeling approaches lack accurate location‐specific direct normal irradiance (DNI), miss a reliable electrical model for power optimization and conversion and are inadequate for optimizing the tracker array configuration. In this paper, a comprehensive modeling of a concentrating photovoltaic system is introduced. First, a more accurate estimation of hourly DNI is obtained by considering location‐dependent DNI and air mass changes according to the sun's elevation. Second, mismatch effects of modules are factored in. Third, various power optimization and conversion levels are taken into account for optimization with self‐shading in each module. The tracker array configuration has been optimized to maximize energy harvest by getting a maximum capacity factor for a given ground coverage ratio. Copyright © 2011 John Wiley & Sons, Ltd.

Improving the wind environment in high-density cities by understanding urban morphology and surface roughness: A study in Hong Kong

In this study, a high-resolution frontal area density (FAD) map that depicts the surface roughness of urban Hong Kong is produced using a mapping method that takes into account the dense urban morphology and the site wind availability of the territory. Using the MM5/CALMET model simulated wind data of Hong Kong, the FAD map of three urban zones are calculated: podium (0–15 m), building (15–60 m), and urban canopy (0–60 m). The wind tunnel test data is used to correlate the FAD understanding of the three zones. The grid sensitivity test indicates that 200 m × 200 m is the reasonable resolution for the FAD map; the test also establishes that the lower urban podium zone yields the best correlation with the experimental data. The study further establishes that the simpler two-dimensional ground coverage ratio (GCR), which is readily available in the planning circle, can be used to predict the area's average pedestrian level urban ventilation performance of the city. Working with their inhouse GIS team using available data, it allows the planners a way to understand the urban ventilation of the city for decisions related to air paths, urban permeability and site porosity.