Contribution to the Investigation of Structure and Origin of the East African Graben by Gravimetry

IntroductionGeophysics as its nameindicates has to do withthe physics of the earth and its surrounding at-mosphere . Gilbert’s discovery that the earth be-haves as a great and rather irregular magnet andNewton’s theory of gravitation may be said toconstitute the beginning of geophysics . Miningand the search of metals date from the earliestti mes , but the scientific record began with thepublicationin 1956 of the famous treatise De remetallica by Georgius Agricola , whichfor manyyears was …     

近40年长株潭生态景观的人为干扰过程分析

以长株潭主城区为研究对象,综合考虑卫星遥感数据、土地利用数据以及地理国情普查数据特点建立长株潭用地类型分类系统,应用土地利用转移矩阵和景观人为干扰测度模型获取主城区用地转移矩阵和人为干扰度指数时空分布,探讨长株潭主城区生态景观与人为干扰之间的关系。结果表明:从土地利用变化角度,1978—2015年长株潭主城区耕地、园林地、建设用地发生了显著变化,耕地总体上呈持续下降趋势,从3 544.67 km~2下降到2 571.18 km~2,园林地呈现先下降后升高的变化趋势,总体下降177.89 km~2;建设用地呈持续上升趋势,从80.56 km~2增加到1 252.85 km~2;在1994—2000年和2010—2015年长株潭主城区土地利用变化两个典型阶段,建设用地的增加主要通过占用耕地和园林地的方式实现。景观人为干扰指数时空分析表明:1978—2015年长株潭主城区景观人为干扰指数高值区主要集中在中心城市和其周边地区,在人类活动的影响下,中心城区以耕地、园林地向建设用地转移为主,周边地区主要以耕地和园林地的相互转移为主;随着城市化进程持续加快,人类活动对主城区生态景观的影响总体呈加强趋势,且受人类活动干扰主要集中在中心城区。     

基于土地利用变化模拟的生态风险动态评价

以松滋市2000年和2010年Landsat TM影像为基础,利用CA-Markov模型并引入土地利用总体规划限制因素,预测松滋市2020年土地利用情况。构建土地利用生态风险指数,运用4 km×4 km的网格模型采样,采用普通克里金插值法进行插值,引入密度分割法进行归一化等级划分,利用GIS工具进行空间叠加分析并制作土地利用生态风险分级图,实现土地利用变化生态风险动态评价,揭示生态风险变化趋势。模拟预测及评价结果显示:1松滋市2000~2020年土地利用结构发生较大变化,耕地、水域和未利用地面积减少,林地和建设用地面积增加。2土地利用生态风险呈逐步升高趋势,由2000年的21.95升高到2020年的88.53,分布以中部及南部较高,西部及东北部较低。32000~2020年分级结果主要以低风险、较低风险及次中风险为主,特高风险区域逐渐增多,生态风险等级以中心城区为中心呈圈层分布,且距离越远生态风险等级越低。     

Spatio-temporal analysis for monitoring urban growth – a case study of Indore City

Urban sprawl is characterized by haphazard patchwork of development, which leads to an improper development in any city. To prevent this kind of sprawl in future, it is necessary to monitor the growth of the city. Hence, an attempt has been made in the present study to monitor the urban growth over a period of time by employing Remote Sensing and Geographic Information System techniques in conjunction with Shannon entropy. Shannon entropy is a measure to determine the compactness or dispersion of built-up land growth in the urban areas. The growth patterns of urban built-up land have been studied initially by dividing the area into four zones. The observations have been made with respect to each zone. Then, the study area has been divided into concentric circles of 1 km buffers and the growth patterns have been studied based on urban built-up density with respect to each circular buffer in all four zones. These observations have been integrated with road network to check the influence of infrastructure on haphazard urban growth. It has been found from the study that Shannon entropy is a good measure to determine the spatial concentration or dispersion of built-up land in the city. The study also proved the potential of RS and GIS techniques in the spatio-temporal analysis of urban growth trends and their consequences in the lands adjoining to urban areas.     

基于光谱特征的雅鲁藏布江源区草地类型识别

以雅鲁藏布江源区为研究对象,以Landsat5 TM图像为数据源,根据不同草地类型的波段组合特征,结合源区1∶100万植被类型图、DEM和NDVI数据,构建草地判别规则,利用决策树分类法对雅鲁藏布江源区草地类型进行遥感识别。研究结果表明:①不同类型草地因其生境不同,利用不同波段组合特征进行草地类型识别能够达到较好的效果;②与传统的监督分类法相比,基于波段组合特征的决策树分类法具有较高的识别精度(总体精度提高了15.4%,Kappa系数提高了0.225);③在海拔4 400～5 000 m区域内,固沙草草原面积最大,其次为矮嵩草和小嵩草混生草甸,再次为变色锦鸡儿和金露梅灌丛,藏北嵩草草甸面积最小。     

CONTROLLING A 1:2500 SCALE ORTHOPHOTOMAPPING PROJECT IN THE UNITED KINGDOM

Orthophotomaps at 1 : 2500 scale, contoured at 1 m vertical intervals, have been produced for an area of 52 km2 from 1 : 10 000 scale photography especially flown for the project. Planimetric and height information on published Ordnance Survey 1 : 2500 scale maps was used as control for the aerial triangulation on which the orthophotomapping was based.     

Orthorectification of IKONOS and impact of different resolution DEM

IKONOS image has been wildly used in city planning, precision agriculture and emergence response. However, the accuracy of IKONOS Geo product is limited due to distortion caused by terrain relief. Orthorectification was performed to remove the distortion and the impact of different DEM on orthorectification were evaluated. 38 ground control points （GCPs） and 25 independent check points （ICPs） were collected. DEMs were generated from 1 ： 10 000 and 1 ： 50 000 topographic maps. Results show that RMS error at the check points is 1. 554 0 m using DEM generated from 1 ： 10 000 topographic map, which can meet the accuracy requirement of IKONOS Precision product （1.9 m RMSE）. While RMS error is 2. 572 4 m using DEM generated from 1 ： 50 000 topographic map.     

城市大比例尺地形图自动化综合的研究

地图自动综合缩编问题一直以来都是个难题。伴着信息化测绘技术的发展,地图自动综合问题逐渐成为热点。随着社会经济与城市建设的飞速发展,城市管理越来越精细化,大比例尺地图的自动综合显得特别的迫切,特别是由1∶500综合到1∶1 000,1∶2 000在城市规划、土地管理等行业的应用具有广泛的需求。     

无人机航空摄影测量系统在农村土地确权中的应用

介绍了用PPSG UAV对双鸭山市郊区2．5 km2地域（农村土地承包经营权确权双鸭山试点）试验区进行无人机航摄,无人机搭载非量测型相机获取低空遥感数据,计算机安装专业空三解算软件处理具体影像,最终取得数字正射影像图（ DOM）、数字表面模型（ DSM）,通过数据分析了该系统的空中三角测量成果的精度和数字正射影像图（ DOM）、数字表面模型（ DSM）的精度,都达到了航空摄影测量地理信息数字成果比例尺1∶1000的成图精度。     

清江流域城镇体系空间结构的GIS分析

清江流域地处湖北省境内,属于经济欠发达地区,城镇化相对滞后,本文利用GIS技术对其城镇体系的空间结构从垂直和水平的角度进行了量化分析,垂直上分为主城、次主城、卫星城、重点镇和一般集镇,结构为1∶1∶11∶3∶98;水平上以主城和次主城作同心圆;交通上以G209、G318、沪蓉高速、宜万铁路和清江作5km缓冲区分析,缓冲区内集中了49%的城镇,沿清江城镇化率最高为39.1%,而所有交通要素的叠加城镇化率仅为20.7%,偏低。卫星城镇多为县市政府所在地,重点镇仅有3个,显然城镇结构还不合理,应加速重点城镇、次主城和主城的建设。     

导航卫星受地球外辐射带影响仿真分析

目前国际上不同国家已经进行了多个导航系统的开发,而构成这些系统的关键空间段实体导航卫星通常分布在中高轨道上,通过地球辐射带对该空间区域内卫星的辐射影响进行仿真分析,对于中轨道空间辐射,当卫星屏蔽厚度大于9mm,再增加屏蔽厚度的方法对辐射隔离不再敏感;对于高轨道空间辐射,当卫星屏蔽厚度大于7mm,再增加屏蔽厚度方法对隔离辐射已经不再敏感。可见,仅从辐射加固角度来说,在卫星设计时,以10年寿命为例,对于中轨道卫星屏蔽厚度区间取[8,9]mm为宜,对于高轨道卫星屏蔽厚度区间取[6,7]mm为宜。     

Mapping the mega paleodrainage basin using shuttle radar topography mission in Eastern Sahara and its impact on the new development projects in Southern Egypt

In the current study, the shuttle radar topography mission (SRTM) data, with ～90 m horizontal resolution, were used to delineate the paleodrainage system and their mega basin extent in the East Sahara area. One mega-drainage basin has been detected, covering an area of 256 000 km2. It is classified into two sub mega basins. The Uweinate sub mega basin, which is composed of four main tributaries, collected water from a vast catchment region and drained eastward from the north, west, and southwest, starting at highland areas. The first subwatershed basin is in the northern plateau, south of the Abu-Balas area, with a total catchment area of 25 045 km2. The second subwatershed is in the Gilf Kebir plateau and has a total catchment area of 38 257 km2. The third subwatershed drains from the Uweinate highlands and has a catchment area of 46 154 km2. The fourth subwatershed, which is known in literature as Wadi Mokhtafi in its upper reach and Wadi Arid in its lower reach, drains the northwestern highlands of Sudan and has a total catchment area of 28 653 km2. The Tushka sub mega basin includes one watershed that drains from the northeast highlands of Sudan and has a total catchment area of 63 019 km2. The Uweinate and Tushka sub mega basins are joined together to the North of the Tushka depression, which drains northward toward the Kharga depression. This study indicates that the Eastern Sahara Mega Basin is a closed hydrological system independent of the other drainage systems, such as the Nile hydrosystem and the Qena Valley system. The present research illustrates the capability of the SRTM data in mapping the paleochannel networks, as well as estimate the catchment area and direction of the water flow. Finally, the study reveals that the four areas could be potentially used for different reclamation activities due to the ground water accumulations possibilities.     

长沙市景观破碎化时空分异特征研究

基于2000年长沙市1:10万土地利用图,利用ERDAS软件对1989年、2006年的遥感图像进行解译;在地理信息系统软件ArcGIS和景观格局分析软件Fragstats支持下,以城镇建设空间重心为中心,分别选取东西、南北景观样带(40 km×8 km)和8个不同半径的同心圆缓冲区,用斑块密度、边界密度、平均斑块分维数...     

Virtual differential GPS based on SBAS signal

In order to access the satellite-based augmentation system (SBAS) service, the end user needs access to the corresponding geostationary earth orbit (GEO) satellites that broadcast the augmentation information for the region. This is normally not a problem for aviation and maritime applications, because an open sky is typically available for such applications. However, it is difficult to access the GEO satellites directly at high latitudes for land applications because of the low elevation angles to the GEO satellites (e.g., 4–22° in Finland to the European geostationary navigation overlay services [EGNOS] GEO satellites). Results from a driving test of 6,100 km in Finland show that the EGNOS GEO satellites can be accessed in only 51.8% of the driving routes. Furthermore, it is also difficult to access the GEO satellites from city canyons, because the high buildings block the GEO signals. This article presents a solution to solve this problem by creating virtual differential GPS (DGPS) reference stations using the SBAS signal in space (SIS). The basic concept is to convert the SBAS signal to Radio Technical Commission for Maritime Services (RTCM) signals, and broadcast the converted RTCM signals over the wireless Internet using the Internet radio technology. Therefore, access to the SBAS service will not be limited by low elevation angles to the GEO satellites because the converted RTCM data streams are disseminated over the wireless Internet. Furthermore, the SBAS service can then be accessed via a legacy DGPS receiver. Two test cases have been carried out with the prototype system developed by the Finnish Geodetic Institute. The test results showed that the positioning accuracy of the virtual DGPS solution was about 1–2 m at 95%, which was similar to that of the standard WAAS/EGNOS solution. The positioning accuracy was not degraded, compared to that of the standard wide area augmentation system–European geostationary navigation overlay services (WAAS/EGNOS) solution, as long as the distance between the rover receiver and the virtual DGPS reference station was less than 150 km. A preliminary driving test of 400 km carried out in southern Finland showed that the availability of the virtual DGPS solutions was 98.6% along the driving route.     

青藏高原湿地遥感监测与变化分析

青藏高原是中国湿地分布较为集中的地区之一,也是全球变化的敏感区.了解青藏高原湿地分布与变化对湿地保护和全球变化研究具有重要意义.基于Landsat 8 OLI (operation land imager)数据,使用面向对象分类方法和人工解译相结合的方式得到2016年青藏高原湿地分布数据,结合2008年湿地分类数据以及...     

基于GIS的土地质量评价研究

以内江市东兴区双桥乡为研究区,建立该区土地质量评价体系,运用层次分析法和基于GIS的图形叠置法对土地质量进行评价,生成了土地质量综合评价图,将内江市东兴区土地质量划分为5个等级,其中质量为优和良好的土地面积总计699.45 km2,约占研究区总面积的72.87%;质量中等的土地面积为184.43 km2,约占总面积的1...     

光学遥感与InSAR结合的金沙江白格滑坡上下游滑坡隐患早期识别

2018-10-11和2018-11-03,金沙江上游西藏自治区江达县波罗乡白格村附近先后发生两次大规模高位滑坡堵江。虽经人工干预处置后进行泄流,但还是对下游居民和交通设施造成了严重损失,其上下游是否还存在类似的大规模滑坡隐患,成为白格滑坡灾害发生后社会各界关注的焦点问题。首先利用高精度光学卫星影像对白格滑坡上游30 km和下游100 km范围内的滑坡隐患进行人工目视解译和定性评价,共识别出滑坡隐患51处,其中下游70~100 km范围内有10处具有堵江风险的滑坡隐患。在此基础上,对具有堵江风险的重点区域（白格滑坡下游70~100 km范围内）收集存档ALOS PALSAR-1和Sentinel-1A雷达卫星数据,利用短基线差分干涉测量技术开展滑坡隐患地表形变定量探测和分析评价,共探测出7处具有较显著形变的滑坡隐患,其中3处堵江风险较大,为白格滑坡上下游地质灾害防治和川藏铁路选线提供了参考。     

Monitoring the Grassland Change in the Qinghai-Tibetan Plateau: A Case Study on Aba County

Located on the southeast edge of the Qinghai-Tibetan plateau, Aba County is the core area of the Returning Grazing Land to Grassland Project (RGLGP) on the plateau. For the purpose of monitoring the grassland change before and after the grassland protection project in Aba County, Landsat images acquired in 1996, 2003 and 2009 were analyzed. Using Spectral Mixture Analysis (SMA) model, sub-pixel fractions of land cover components were obtained: bright vegetation (BV), dark vegetation (DV), bright soil (BS), dark soil (DS) and water. Fraction images present the distribution and proportions of typical land cover components in this study. Fractions BV and BS were chosen as two indicators for grassland degradation. Thereafter, Change Vector Analysis (CVA) model was applied on the two indicators. After the performance of the CVA model, change results which consisted of both grassland degradation and vegetation re-growth were obtained, showing the change patterns of grassland degradation and vegetation re-growing in Aba County between two gaps: from 1996 to 2003 (before the RGLGP) and from 2003 to 2009 (after the RGLGP). The change patterns of grassland degradation and vegetation re-growing can effectively assist in the development of environmental restoration measures and in the RGLGP plans for the Qinghai-Tibetan plateau.     

Closed formulas for the direct and reverse geodetic problems

A new solution of the direct and reverse geodetic problems has been deduced without series expansion or coordinate transformation. The unknown parameters are directly expressed as explicit functions of the given parameters; the forms of the functions are closed formulas deduced by elementary mathematics using the chord of normal section. Numerical examples prove that the formulas are valid for distances from 40 km to 15 000 km on the surface of the ellipsoid.     

Investigation of the ground displacement in Saint Petersburg,Russia, using multiple-track differential synthetic aperture radar interferometry

Global sea level rise and local land subsidence might exacerbate the risk of flooding in coastal plains. Among other cities, this is also the case for the high-latitude city of St. Petersburg, which has long been threatened by flood events. To protect the urban area from storm surges, the Union of Soviet Socialist Republics (USSR) in 1978 approved the construction of the 25 km long Flood Prevention Facility Complex (FPFC), which was completed in 2011. The risk of flooding in the city area of St. Petersburg is amplified by the fact that large sections of the coastal area have been reclaimed from the sea. In this study, we investigate the temporal evolution of the ground displacement in St. Petersburg. To this end, we perform an extended analysis based on the application of a simplified version of the differential interferometric synthetic aperture radar technique, known as the minimum acceleration (MinA) approach. The MinA algorithm is a multi-satellite/multi-track interferometric combination technique that allows working with multiple sets of SAR images. The method allowed generation of time series of two-dimensional (2-D) (i.e. East-West and Up-Down) deformation of the terrain by processing two sequences of Sentinel-1A/B (S-1A/B) SAR images acquired from 2016 to 2018, along the ascending and descending flight passes. The Small BAseline Subset (SBAS) algorithm was independently applied to the two sets of SAR data to generate the relevant Line-Of-Sight (LOS)-projected ground deformation time series. Subsequently, the LOS-projected deformation products were geocoded and jointly combined. The results indicate that the deformation in the city is predominantly vertical (i.e. it is subsiding) with a maximum subsidence rate of about 20 mm/year corresponding to the newly sea-reclaimed lands. Finally, the error budget of the retrieved 2-D deformation time series has also been addressed.