Modelling and Mapping Damage to Forests from an Ice Storm Using Remote Sensing and Environmental Data

An extreme ice storm in January 1998 deposited up to 100 mm of ice and resulted in significant forest damage across eastern North America. Average crown loss of over 75% was recorded in large areas of eastern Ontario and southern Quebec. A primary question that arose following the storm was: can forest damage be effectively assessed using remote sensing and other available environmental data? This paper presents two contrasting studies to address this question. The first involves damage modelling at a local scale in an unmanaged forest using spectral and spatial information in high-resolution airborne imagery. Results of field data analyses are also given that show relations between damage and forest structure and composition as well as changes in forest structure that occurred in the years following the storm. The second study involves regional scale damage mapping in managed and unmanaged forests of eastern Ontario using medium resolution satellite imagery and other environmental data. In comparison of several image classification and data interpolation methods, the best damage map was produced using a neural network classifier and a mix of Landsat and environmental data. The methods and results presented in this paper form the basis for ongoing long-term temporal study of damage impacts on forest condition.     

Potential of Satellite Remote Sensing and GIS for Landslide Hazard Assessment in Southern Kyrgyzstan (Central Asia)

Big landslides are one of the main natural hazards in Kyrgyzstan, which are concentrated in the foothills of the high mountain ranges along the Eastern rim of the Fergana Basin. Because of the high number of landslides and their occurrence over large areas there is a strong need for effective and objective landslide hazard assessment at a regional scale. In Kyrgyzstan satellite remote sensing data represent the only source of multitemporal information about surface conditions covering large areas. Against this background the goal is the development of a satellite remote sensing and GIS-based system for quantitatively oriented and spatially differentiated hazard assessment. During the presented pilot investigations in the area of the Upper Maili Suu river basin a methodological framework has been developed incorporating remote sensing and GIS techniques for various levels of information extraction. So far, methodological investigations have been focused on the potential of satellite remote sensing data from different optical (Landsat-(E)TM, ASTER, MOMS-2P) and radar (ERS-1/2) systems for the creation of an improved knowledge basis for hazard assessment. This includes landslide identification, generation of topographic information and characterization of the geological setting. The derived primary information have been analyzed in a GIS environment to gain an improved process understanding as a main prerequisite for successful hazard assessment. The results show that currently available satellite remote sensing data are suitable for landslide investigation in Kyrgyzstan. Full exploitation of their information potential requires combined analysis with other thematic information based on methods of interactive and automated information extraction.     

针对MODIS数据的大气水汽含量反演及31和32波段透过率计算

 针对MODIS的波段特征,首先,用近红外波段反演大气水汽含量; 然后,通过LOWTRAN模拟大气水汽含量与MODIS 31和32热红 外波段透过率的统计关系; 最后,计算31和32波段的透过率。该方法克服了以往一景图像只用1个透过率的局限性,使得透过率的求 算精确到每1个像元,同时保证参数获取的实时性。     

二维CCD图象数据压缩

本文着重指出了在今后处理大面积CCD图象数据过程中,所将面临的数据存贮困难问题.本文提出了一种有效的不丢失天文信息的压缩CCD图象数据的方法,对银纬b=-60°的一个天区的试验表明,压缩后的图象数据仅为原图象数据的1/30左右,并且可以十分方便地进行图象再现及再处理。在压缩数据过程中,我们在剑桥APM底片扫描机参数化施密特照相底片的基础上,重新安排了CCD图象上天体的对应参数,并视天体的大小及形状,有效地提取保存了天体周围矩阵信息.     

用CCD照相多幅叠加处理检测弱星的试验

本文利用CCD动态范围大且便于数值处理的优点,观测月晕中(强背景上)的弱源。在背景尚未使CCD片子饱和时,即停止露光,存入计算机,多次露光,然后在计算机内多幅叠加,减去背景,显出弱源。通过观测试验和定量估算,结果表明,曝光重叠法,用10幅图叠加时能提高信噪比2.65倍。实测与理想情况符合较好。     

遥感图象的马尔柯夫随机场模型的纹理识别方法

本文讨论了马尔柯夫随机场图象模型及邻域选择方法,提出了8邻域5特征参数的马尔柯夫随机场图象模型以及一套完整而有效的特征参数的估计算法,将这些特征参数变成可视图象从而实现了视算。对8类不同纹理的标准图象进行分类试验,其识别(分类)的平均正确率达97.57％。     

A Model to Calculate what a Remote Sensor ‘Sees’ of an Urban Surface

Whilst the measurement of radiation emissions from a surface is relatively straightforward, correct interpretation and proper utilization of the information requires that the surface area seen be known accurately. This becomes non-trivial when the target is an urban surface, due to its complex three-dimensional form and the different thermal, radiative and moisture properties of its myriad surface facets. The geometric structure creates shade patterns in combination with the solar beam and obscures portions of the surface from the sensor, depending on where it is pointing and its field-of-view (FOV). A model to calculate these surface-sensor-sun relations (SUM) is described. SUM is tested against field and scale model observations, and theoretical calculations, and found to perform well. It can predict the surface area seen by a sensor of known FOV pointing in any direction when placed at any point in space above a specified urban surface structure. Moreover, SUM can predict the view factors of the roof, wall and ground facets seen and whether they are sunlit or shaded at any location and time of day. SUM can be used to determine the optimal placement and orientation of remote sensors to study urban radiation emissions; if the facet temperatures are known or modelled it can calculate the average temperature of the system, and it can determine the directional variation of temperature (anisotropy) due to any particular surface-sensor-sun geometric combination. The present surface geometry used in SUM is relatively simple, but there is scope to make it increasingly realistic.     

A portable remote methane detector using an InGaAsP DFB laser

A portable remote methane detector based on infrared-absorption spectroscopy using an InGaAsP distributed-feedback laser is described. This equipment transmits a laser beam and detects a fraction of the backscatter reflected from the target. From this, the detector thereby measures the integrated methane concentration between the detector and the target. The equipment operator can easily detect methane clouds at a distance by hand-scanning the laser beam. To achieve a high sensitivity of detection, wavelength-modulation spectroscopy is applied to the infrared-absorption measurement for methane. The wavelength of the light source is modulated at a frequency of 10 kHz, and the center wavelength is stabilized at the center of the 2₃ band R(3) line of methane (1.65372 m). When used with typical targets at distances up to 10 m, the detector has a detection limit of less than 5 ppm-m. To the best of the authors knowledge, the detector is the only hand-held product capable of remote methane detection. Recently, this novel equipment was commercially introduced into the Japanese market as a product named the Portable Remote Methane Detector (PRMD). Some PRMD units were in research use for detecting methane emissions from garbage landfills, although the PRMD was mainly developed for remote detection of leaks from natural gas pipelines. The author expects that the PRMD could become the standard equipment for field measurements of methane emissions from land.     

高光谱--遥感测绘的新机遇

通过对高光谱遥感技术的主要优势、基本特征和地理空间信息探测潜力的分析,展示了高光谱数据在遥感测绘领域大规模应用的可能性.同时,还分析了围绕高光谱测绘应用相关的一系列问题,包括高光谱数据的测绘需求、面向测绘应用的高光谱影像分析的关键技术、高光谱遥感测绘模式以及实用化系统建立的设想等.通过对这些问题的进一步深化研究,高光谱技术就可充分与现有的遥感测绘手段有机结合,并对地理空间信息的遥感探测技术产生有力的推动.     

抚顺市市区地质灾害遥感调查研究

抚顺市是中国重要的大型煤炭工业基地之一。由于长期的采掘施工,其采矿场和采矿坑不断扩大加深,导致了矿区及其周边地带地面不稳定性的不断加剧,且已发生了局部的地面沉降等地质灾害,给人们的生产和生活带来了直接的威胁,并严重地影响着该地区社会经济的可持续发展。本研究工作采用遥感技术手段,快速地查明该地区现有的地质灾害类型、数量及其表现形式,以及地质灾害与断裂构造的相互关系,从而为在该地区进行地质灾害防治工作提供准确可靠的依据,取得了良好的应用效果。