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With the development of urban built-up areas, accurately extracting the urban built-up area and spatiotemporal pattern evolution trends could be valuable for understanding urban sprawl and human activities. Considering the coarse spatial resolution of nighttime light (NTL) data and the inaccurate regional boundary reflection on point of interest (POI) data, land surface temperature (LST) data were introduced. A composite index method (LJ–POI–LST) was proposed based on the positive relationship for extracting the boundary and reflecting the spatial-temporal evolution of urban built-up areas involving the NTL, POIs, and LST data from 1993 to 2018 in this paper. This paper yielded the following results: (1) There was a spatial-temporal pattern evolution from north-east to south-west with a primary quadrant orientation of IV, V, and VI in the Hefei urban area from 1993–2018. The medium-speed expansion rate, with an average value of 14.3 km2/a, was much faster than the population growth rate. The elasticity expansion coefficient of urbanization of 1.93 indicated the incongruous growth rate between the urban area and population, leading to an incoordinate and unreasonable development trend in Hefei City. (2) The detailed extraction accuracy for urban and rural junctions, urban forest parks, and other error-prone areas was improved, and the landscape connectivity and fragmentation were optimized according to the LJ–POI–LST composite index based on a high-resolution remote sensing validation image in the internal spatial structure. (3) Compared to the conventional NTL data and the LJ–POI index, the LJ–POI–LST composite index method displayed an extraction accuracy greater than 85%, with a similar statistical and landscape pattern index result. This paper provides a suitable method for the positive relationship among these LST, NTL, and POI data for accurately extracting the boundary and reflecting the spatial-temporal evolution of urban built-up areas by the fusion data. [ABSTRACT FROM AUTHOR]

• First presented a universal canopy gap fraction (GF) model for forests with various tree distributions. • Accuracy of canopy GF at off-nadir is significantly improved by the new model. • Universality and accuracy of the universal model are validated by a ray-tracing method. • Universal model form the backbone of the development of a potentially universal canopy reflectance model. An accurate estimation of forest canopy gap fraction (GF) is a prerequisite for remote sensing retrievals of several associated canopy parameters e.g. leaf area index, fAPAR (fraction of photosynthetically active radiation absorbed by the canopy), clumping index, etc. A universal canopy GF model for forests is required for various tree distribution patterns on flat and slopping terrains, yet existing models so far do not possess all these abilities simultaneously. For example, the Neyman type-A model, the Poisson model, and the hypergeometric model are suitable only to forests with clumped, random, and regular tree distributions, respectively. In this regard, the suite of Nilson's canopy GF models developed for forests with various tree distributions have the potential to become universal models. For this purpose, this study attempts to overcome the following limitations of these models to make them be true universally applicable: (1) canopy GF calculated by the Nilson's models is mostly accurate for various tree distributions at nadir; whereas at it is either underestimated for clumped tree distributions or overestimated for regular tree distributions at off-nadir; and (2) Nilson's models were developed for flat terrains and untested for sloping terrains. Herein, two Nilson's models are modified by expanding the calculation of overlaps among crowns (OAC) at nadir to the whole hemispherical space. The results show that all canopy GF simulations in the new models (New91 and New99) show higher consistency with ray-tracing results than those in original Nilson's models in all directions, highlighting the need to consider directional OAC. The modified models (especially for New99) are validated in two RAMI forest stands and a Saihanba forest stand: the relative error in canopy GF between the modified models and a ray-tracing model is less than 10 % in all forest stands. The modified models (especially New99) are suitable for various tree distributions on flat and slopping terrains and therefore increased the universality of the original Nilson's models suitable for a wide-range of remote sensing applications. New99 can be deemed as a universal canopy GF model for forests with various tree distributions. [ABSTRACT FROM AUTHOR]

Geometric-optical (GO) model suitable for forest plantation (GOFP) is a GO model for forest plantations at the stand level developed in this study based on a four-scale GO model a Geometric-Optical Model for Sloping Terrains-II (GOST2), which simulates the bidirectional reflectance distribution function (BRDF) for natural forest canopies. In most previous GO models, tree distributions are often assumed to meet the Poisson or Neyman model in a forest; therefore, these models are suitable for simulating BRDF for natural forest canopies. However, in forest plantations, tree distributions are proven to meet the hypergeometric model rather than the Poisson or Neyman model at the stand level. GOFP, in which the tree distributions are described using the hypergeometric model, is proposed to simulate the bidirectional reflectance factor (BRF) of forest plantations at the stand level. The area ratios of the four scene components (sunlit foliage, sunlit ground, shaded foliage, and shaded ground) of GOFP compare well with those simulated by a 3-D canopy visualization technique. A comparison is also made against discrete anisotropic radiative transfer, showing that GOFP has the ability to simulate BRF of forest plantations. Another comparison is made against operational land imager and Moderate Resolution Imaging Spectroradiometer surface reflectance, showing that GOFP with the hypergeometric model outperforms GOST2 with the Poisson and Neyman models. The results further show that the differences in BRFs between GOFP and GOST2 pronouncedly increase with the difference between the reflectance of sunlit foliage ( RT ) and the reflectance of sunlit ground ( RG ), as well as the distances among trees and the number of crowns in a forest plantation, suggesting that GOFP significantly outperforms GOST2 for simulating BRF of forest plantations. [ABSTRACT FROM PUBLISHER]

• Quantitative studies on the infrared radiation temperature fields on rock surfaces caused by stress variations and fracture by standard deviational ellipse. • The inflection point on the curve of the ellipse parameters occurred earlier than that on the AIRT and standard deviation curves in the microfracture development stage. • In the fracture development stage, the area of the ellipse decreased, while the ellipticity increased. The shape of the ellipse changed from circular to striped. Previous studies focused mainly on the temporal analyses of thermal infrared radiation variations based on statistical parameters for rocks under loading conditions, and the spatial features were qualitatively obtained by visual interpretation. Hence, quantitative studies on the infrared radiation temperature fields on rock surfaces caused by stress variations and fracture activity remain scarce. Therefore, the standard deviational ellipse algorithm was introduced into spatial statistical analysis based on a temporal analysis. First, the abnormal infrared temperature points with values exceeding three times the standard deviation were extracted according to the statistical results for the entire calculated region, and the spatial coordinates of those abnormal points at different loading times were obtained. Second, the standard deviational ellipse was plotted based on the spatial coordinates of the abnormal points, and the lengths of the axes parallel and perpendicular to the loading direction, the coordinates of the ellipse center, and the area and ellipticity of the ellipse can be calculated at a certain loading moment. Then, the continuous temporal curves of the ellipse parameters during the whole loading process can be plotted, and quantitative analysis can be carried out on the spatiotemporal characteristics. The ellipse parameters changed steadily in the elastic stage, and the inflection point on the curves of the ellipse parameters occurred earlier than the inflection point on the curves of the average infrared radiation temperature and standard deviation in the microfracture development stage. The length of the coordinate axis perpendicular to the loading direction exhibited a decreasing trend. In the fracture development stage, the area of the ellipse decreased, and the ellipticity increased; the coverage region decreased, and the shape of the ellipse changed from circular to elongated. The ellipse parameters can quantitatively describe the evolution trend of the infrared radiation temperature field on the rock surface from a uniform random distribution to a centralized distribution in the fracture area, and the moving direction of the ellipse center can roughly indicate the macrofracture location. These research results are expected to provide experimental data-based guidance for the comprehensive quantitative analysis of temporal-spatial characteristics for the monitoring of rock stress disasters by thermal infrared remote sensing. [ABSTRACT FROM AUTHOR]