Optimal Model for Geoid Determination from Airborne Gravity

Two different approaches for transformation of airborne gravity disturbances, derived from gravity observations at low-elevation flying platforms, into geoidal undulations are formulated, tested and discussed in this contribution. Their mathematical models are based on Green's integral equations. They are in these two approaches defined at two different levels and also applied in a mutually reversed order. While one of these approaches corresponds to the classical method commonly applied in processing of ground gravity data, the other approach represents a new method for processing of gravity data in geoid determination that is unique to airborne gravimetry. Although theoretically equivalent in the continuous sense, both approaches are tested numerically for possible numerical advantages, especially due to the inverse of discretized Fredholm's integral equation of the first kind applied on different data. High-frequency synthetic gravity data burdened by the 2-mGal random noise, that are expected from current airborne gravity systems, are used for numerical testing. The results show that both approaches can deliver for the given data a comparable cm-level accuracy of the geoidal undulations. The new approach has, however, significantly higher computational efficiency. It would be thus recommended for real life geoid computations. Additional errors related to regularization of gravity data and the geoid, and to accuracy of the reference field, that would further deteriorate the quality of estimated geoidal undulations, are not considered in this study.     

The influence of alongshore and cross‐shore wave energy flux on large‐ and small‐scale coastal erosion patterns

A strong low‐pressure system traveled along the Japanese main island Honshu in October 2006. High waves and storm surge attacked the Kashima Coast resulting in huge erosion over the area. Airborne laser data measured in October 2005 and November 2006 were analyzed to estimate cross‐sectional changes within the subaerial zone. The results of the alongshore distribution of the changes of cross‐sectional area indicate that the amount of erosion of the 38 km‐long northern and 15 km‐long southern parts decreased toward the south in each part and that the amount of erosion was smaller in protected areas with artificial headlands than in unprotected areas. The local alongshore variation of the erosion and accretion patterns showed wavy fluctuations of several hundreds of meters. The total amounts of the estimated eroded volume of the subaerial zone over the northern and southern parts were 620 000 m³ and 600 000 m³, respectively. The Simulating Waves Nearshore (SWAN) wave model was applied to estimate wave conditions along the coast during the storm. The computational results were verified, and then the alongshore distribution of wave energies, expressed as the alongshore and cross‐shore components of the wave energy flux, was compared with the alongshore distribution of cross‐sectional change. The results show that the distribution of energy flux explains the distribution of erosion well: The alongshore variability in the cross‐shore energy flux is responsible for the large‐scale variability in erosion, and shorter‐scale variability is due to gradients in the alongshore energy fluxes, especially for the areas without coastal works. Copyright © 2011 John Wiley & Sons, Ltd.     

Quantitative estimation of submarine groundwater discharge using airborne thermal infrared data acquired at two different tidal heights

Submarine groundwater discharge (SGD) plays an important role in coastal biogeochemical processes and hydrological cycles, particularly off volcanic islands in oligotrophic oceans. However, the spatial and temporal variations of SGD are still poorly understood owing to difficulty in taking rapid SGD measurements over a large scale. In this study, we used four airborne thermal infrared surveys (twice each during high and low tides) to quantify the spatiotemporal variations of SGD over the entire coast of Jeju Island, Korea. On the basis of an analytical model, we found a linear positive correlation between the thermal anomaly and squares of the groundwater discharge velocity and a negative exponential correlation between the anomaly and water depth (including tide height and bathymetry). We then derived a new equation for quantitatively estimating the SGD flow rates from thermal anomalies acquired at two different tide heights. The proposed method was validated with the measured SGD flow rates using a current meter at Gongcheonpo Beach. We believe that the method can be effectively applied for rapid estimation of SGD over coastal areas, where fresh groundwater discharge is significant, using airborne thermal infrared surveys.     

Stormflow dynamics and loads of Escherichia coli in a large mixed land use catchment

Storm events are major transporters of faecal microbial contaminants, but few studies have reported storm loads or concentration dynamics in relation to discharge or other pollutants, notably fine sediment. Episodically, high loads of faecal contamination during storm flows impact downstream uses of water bodies, particularly contact recreation and shellfish harvesting. We examined the storm dynamics of Escherichia coli, turbidity and discharge in the mixed land use Motueka catchment (2047 km²; 60% forest and 19% pasture) to gain insights into E. coli sources and transport. We also explored different approaches for calculating E. coli loads. Discharge and field turbidity were recorded continuously, and E. coli concentrations were sampled during events, over a 13‐month period near the mouth of the Motueka River. E. coli loads were estimated by interpolation, averaging estimators and by using linear regression with smearing correction of the log‐transformed variables: discharge, turbidity, and both turbidity and discharge. The annual E. coli load was dominated (～98%) by export during events. Comparison of monthly monitoring with the intensive storm monitoring campaign suggests that simple stratification of the sampling into storm and baseflow would greatly improve export estimates. E. coli peak concentrations always preceded discharge and turbidity peaks (which had similar timing). Turbidity can be a useful surrogate for faecal microbes in smaller catchments, but in the Motueka turbidity was no better for predicting E. coli concentration than discharge. Runoff from grazed pasture and direct deposition from livestock are probably the ultimate E. coli sources in the Motueka catchment. However, in‐channel stores seem to dominate E. coli dynamics during events and account for the typical feature of bacterial concentrations peaking ahead of discharge and turbidity. This study demonstrates the importance of storm events to faecal microbial loads and shows that E. coli concentration dynamics may contrast with those of turbidity. Copyright © 2009 John Wiley & Sons, Ltd.     

Integrating airborne and multi‐temporal long‐range terrestrial laser scanning with total station measurements for mapping and monitoring a compound slow moving rock slide

A slow moving compound rock slide located in the northern Apennines of Italy was mapped and monitored through the integration of Airborne Laser Scanning (ALS), multi‐temporal long‐range Terrestrial Laser Scanning (TLS), and Automated Total Station (ATS) measurements. Landslide features were mapped using a High Resolution Digital Terrain Model (HR‐DTM) obtained by merging ALS and TLS data in an Iterative Closest Point (ICP) procedure. Slope movements in the order of centimeters to a few decimeters were quantified with Differential TLS (D‐TLS) based on a Surface Matching approach and supported by ATS data to define stable reference surfaces. The integrated approach allowed mapping of the composite geomorphic features of the rock slide under examination, revealing its complex dynamic nature and further proving that laser scanning is a versatile and widely applicable tool for slope process analysis. Copyright © 2013 John Wiley & Sons, Ltd.     

航空甚低频电磁异常在胶东牟乳地区构造填图中的应用

通过对胶东牟平－乳山地区１：２．５万航空甚低频电磁异常的分析研究，并结合航磁，航放、遥感以及区域构造地质资料，进行了构造地质填图，首次进一步证实了被前人所忽视的近东西向断裂构造的存在，并给予了准确定位。在此基础上进行了金矿成矿远景预测，取得了比较满意的效果。     

利用遥感光谱特征提取岩性信息的基础和技术研究

地物光谱特征的研究是遥感技术的基础研究工作之一．从光谱遥感发展与地质应用的趋势出发。从光谱遥感岩矿识别基础与识别技术方法两方面阐述了光谱遥感的研究进展．在技术方法方面，主要从多光谱与成像光谱以及遥感与航空放射性信息集成3个层次上，分析利用光谱特征进行岩石矿物识别的研究进展及其潜力与可行性，并简单阐述了遥感与航空放射性信息的复合这一遥感岩性信息识别研究的发展趋势．     

航空电磁法在黄河口地区寻找浅层淡水的地质效果

对利用航空电磁法寻找浅层淡水的方法技术进行了探索,根据找水需要编制了保留区域场的三频标差异常图,对本区的海侵界线及海侵程度进行了研究,并在咸水区内圈定浅层淡水远景区29处,对各淡水远景区进行了分析与评价.     

TRMM卫星与机载雷达在降雨反演中的数据对比个例研究

热带降水测量卫星（TRMM）上搭载的测雨雷达是第一部能够提供三维降水信息的星载雷达,机载雷达也能够对降雨进行实时观测。由于机载和星载雷达观测有很多共同点,所以选择机载、星载雷达数据进行对比。1998年8月26日NOAA/P3飞机对Bonnie飓风进行了一次观测飞行,与此同时TRMM卫星也同步扫过该区域,因此利用对Bonnie飓风的机、星观测数据对应点数值对比、差值对比、平均值对比等,对Bonnie飓风做了进一步分析。对比结果一致,印证了TRMM数据的可靠性,同时进一步验证了双束立体雷达算法的联合算法的可靠性。