Performance of image classification on hyperspectral imagery for lithological mapping

SVM and SAM classifiers for the lithological mapping using Hyperion data in parts of Gadag schist belt of western Dharwar craton, Karnataka, India were used. The main objective of the present study is to assess and compare the potential use of Hyperion data set for lithological mapping. Accuracy assessment of the derived thematic maps was based on the analysis of the confusion matrix statistics computed for each classification map. For consistency, the same set of validation points were used in evaluating the accuracy of the lithological thematic maps produced. On the basis of the accuracy assessment results, it appears that SVM generally outperformed the SAM classifier in both OA accuracy and individual classes’ accuracies. OA accuracy and Kc for SVM is 96.93% and 0.9655, whereas for SAM it is 74.02% and 0.7085 respectively. SVM classification is the best in describing the spatial distribution and the cover density of each lithology, as was also indicated from the statistics of the individual class results. The individual class accuracy were also analyzed for the SVM and the result show that PA ranges from 87% to 100% and UA ranges from 91% to 100%, whereas for SAM ranges from 15% to 95%, and from 31% to 100% respectively. The SVM method could effectively classify and improve on the existing geological map for the Gadag schist belt (GSB) using hyperspectral data. The results could be validated through field visits. Therefore, it is concluded that hyperspectral remote sensing data can be efficiently used to improve existing maps, especially in areas where same rock types show variable degree of alteration over smaller spatial scales.     

Numerical simulation of ship stability for dynamic environment

The prediction of ship stability during the early stages of design is very important from the point of vessel’s safety. Out of the six motions of a ship, the critical motion leading to capsize of a vessel is the rolling motion. In the present study, particular attention is paid to the performance of a ship in beam sea. The linear ship response in waves is evaluated using strip theory. Critical condition in the rolling motion of a ship is when it is subjected to synchronous beam waves. In this paper, a nonlinear approach has been tried to predict the roll response of a vessel. Various representations of damping and restoring terms found in the literature are investigated. A parametric investigation is undertaken to identify the effect of a number of key parameters like wave amplitude, wave frequency, metacentric height, etc.     

Towards estimating root‐zone soil moisture using surface multispectral and thermal sensing: A spectral and hydrometeorological dataset from the Dookie experiment site,Victoria, Australia

This paper describes surface hydrometeorological and spectral datasets collected from two tower sites located in the University of Melbourne's Dookie experimental farm, Victoria, Australia. The datasets were collected from different vegetation types including wheat, canola, and grazed pasture during the 2012, 2013, and 2014 cropping seasons. The dataset includes 30‐min frequency latent and sensible heat flux measurements and layer‐average soil moisture data at profile depths of 0–5, 0–30, 30–60, 60–90, and 90–120 cm. Air temperature, wind speed, wind direction, relative humidity, precipitation, and incoming and outgoing longwave and shortwave radiation data were also collected from two locations in the study area. The dataset described in this paper is available online.     

GCP collection for corona satellite photographs: Issues and methodology

Use of high-resolution and historic CORONA satellite photographs for mapping and other purposes requires Ground Control Points (GCPs), as ephemeris data and image parameters are not available. However, the alterations in landscape in last 34 years (i.e., since the acquisition of these photographs) prevent identification and collection of large number of GCPs in the field. This paper presents a methodology for collection of GCPs for CORONA photographs. The advantages and limitations of the methodology are discussed. For a study site, situated in Siwaliks and Lower Himalayas, the GCPs were identified in CORONA photographs and their WGS84 coordinates were estimated through a process of datum transformation and georeferencing. Estimated GCP coordinates from the topo sheets and 2D and 3D views of photographs, helped in identifying the GCP locations in field, which were observed using DGPS. Investigations were carried out to relate Differential Global Positioning System (DGPS) accuracy with base line length and time of observation. Abase line of 350 km and half an hour observation were found appropriate to yield accuracy in GCP collection by DGPS method, which conforms to CORONA resolution of 3 m.     

Inversion of gravity and magnetic anomalies over some bodies of simple geometric shape

The general expression for gravity and magnetic anomalies over thin sheets and sloping contacts may be expressed as a polynomial of the formFx ²+C₁Fx+C₂F+C₃x³+C₄x²+C₅x+C₆. The initial parameters of the source are obtained from the coefficientsC ₁, C₂,..., C₆ which may be solved by inverting a 6×6 matrix. The initial parameters are modified by successive iteration process using the difference formula until the root mean square error between the observed and calculated anomalies is a minimum. The regional background which may be in the form of a polynomial is estimated by the computer itself. This method is applied on a number of field anomalies and is found to yield reliable estimates of depth and other parameters of the source.     

2000—2015年夏秋季孟加拉湾湾口区涡流相互作用能量学特征

文章主要使用全球简单海洋资料同化分析系统(Simple Ocean Data Assimilation, SODA)产出的海洋再分析数据产品和美国国家环境预报中心(National Centers for Environmental Prediction, NCEP)发布的风场资料, 通过能量学方法分析了2000—2015年夏季至秋季(6—11月)孟加拉湾涡-流相互作用特征在不同印度洋偶极子(Indian Ocean Dipole, IOD)事件发生年的表现。结果表明, 在IOD负位相年更强的西南季风背景下, 涡动能和涡势能的量值均较大, 海洋不稳定过程更多地将平均流场的能量输向涡旋场, IOD正位相年反之。另外, 研究发现孟加拉湾湾口区的涡动能在个别年份会发展出一种与气候态存在显著异常的空间分布, 即在个别年份湾口中央海域异常出现涡动能极大值。通过对出现该异常现象最显著的2010年进行个例分析, 发现当年的孟加拉湾海表风场发展出一个气旋式环流异常, 显著地改变了海洋上层环流形态, 极大地影响了平均流场与涡旋场之间的相互作用。进一步对维持涡动能平衡的各做功项进行诊断后发现, 湾口异常海域涡动能年际变化的主要影响因素为海洋内部的压强做功, 其次是正压不稳定过程和平流的做功, 海表风应力做功项贡献较小。     

Automated Approach for Extraction of Oil Spill from SAR Imagery

Oil spill pollution is a major environmental concern since it has most dangerous and hazardous effects on marine environment. Periodic monitoring by detecting oil spills along with its movement, helps in efficient clean-up and recovery operations. Over the past few years, Synthetic Aperture Radar (SAR) based remote sensing has received considerable attention for monitoring and detecting oil spill due to its unique capabilities to provide wide-area observation in all weather conditions. However, the interpretation of marine SAR imagery is often ambiguous, since it is difficult to separate oil spill from look-alike features. The objective behind our study was to extract probable oil spill candidates automatically from SAR imageries containing oil spill incidences, where new methods based on over-segmentation and amalgamate approach is used for this purpose. The methodology is all about over segmenting the entire image based on its statistics and amalgamating relevant segments at later point of time to represent actual dark features as probable oil spill candidates. Under the dependency on SAR imageries alone, the approach does not take care of the separation of look-alike features which can be addressed subsequently by the consideration of associated synchronous external data resources such as optical data, wind and ocean parameters (Zhao et al. in Opt Express 22(11):13755–13772, 2014; Espedal and Wahl in Int J Remote Sens 20(1):49–65, 1999). The approach is carried out on a set of RISAT-1 imagery containing oil spill incidences and the extracted oil spill areas are in well agreement with the visually interpreted output with kappa coefficient greater than 0.70 and overall classification accuracy greater than 80%.     

Multi-Physics ensemble prediction of tropical cyclone movement over Bay of Bengal

Ensemble prediction methodology based on variations in physical process parameterizations in tropical cyclone track prediction has been assessed. Advanced Research Weather Research and Forecasting model with 30-km resolution was used to make 5-day simulation of the movement of Orissa super cyclone (1999), one of the most intense tropical cyclones over the North Indian Ocean. Altogether 36 ensemble members with all possible combinations of three cumulus convection, two planetary boundary layer and six cloud microphysics parameterization schemes were produced. A comparison of individual members indicated that Kain–Fritsch cumulus convection scheme, Mellor–Yamada–Janjic planetary boundary layer scheme and Purdue Lin cloud microphysics scheme showed better performance. The best possible ensemble formulation is identified based on SPREAD and root mean square error (RMSE). While the individual members had track errors ranging from 96–240 km at 24 h to 50–803 km at 120 h, most of the ensemble predictions show significant betterment with mean errors less than 130 km up to 120 h. The convection ensembles had large spread of the cluster, and boundary layer ensembles had significant error disparity, indicating their important roles in the movement of tropical cyclones. Six-member ensemble predictions with cloud microphysics schemes of LIN, WSM5, and WSM6 produce the best predictions with least of RMSE, and large SPREAD indicates the need for inclusion of all possible hydrometeors in the simulation and that six-member ensemble is sufficient to produce the best ensemble prediction of tropical cyclone tracks over Bay of Bengal.     

Implications of vortex initialization and model spin-up in tropical cyclone prediction using Advanced Research Weather Research and Forecasting Model

The roles of vortex initialization and model spin-up in tropical cyclone (TC) prediction using Advanced Research Weather Research and Forecasting (ARW) Model are studied through a case study of NARGIS (2008) cyclone over Bay of Bengal. ARW model is designed to have three two-way interactive nested domains, and a suite of 36 numerical experiments are performed with three values of maximum wind (MW), four of radius of maximum wind (RMW), and three of α and one experiment without vortex initialization. The results indicate that vortex initialization is important toward realistic representation of initial structure and location of cyclone vortex. Model spin-up during the first 18–24 h of model integration lead to faster intensification than of the real atmosphere, thus a weaker initial vortex evolved more realistically. Three experiments from vortex initialization produced MW and RMW nearer to the observations, but none of these produced a good prediction due to unrealistic intensification during model spin-up. A weaker vortex with intensity less than 50 % than observations produced the best forecast in terms of intensity, track, and landfall. The results suggest that slightly larger (~30 %) RMW than observations with α as ?0.5 (for 81 km model resolution) that produces weaker vortex is to be implemented in the design of bogus vortex. This study assesses the merits of TC bogus scheme in ARW model, illustrates the need for vortex initialization, and analyzes the spin-up problem in cold-start model simulations of TC prediction.