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133.
农业遥感研究应用进展与展望 总被引:22,自引:0,他引:22
得益于中国自主遥感卫星、无人机遥感和物联网等技术的发展,中国农业遥感研究与应用在过去20年取得了显著进步,中国农业遥感信息获取呈现出天地网一体化的趋势;农业定量遥感在关键参数遥感反演技术方法与应用方面取得进展;作物面积、长势、产量、灾害遥感监测的理论与技术方法取得突破,农业遥感技术应用领域不断拓展。本文从农业遥感信息获取、农业定量遥感、农业灾害遥感、作物遥感识别与制图、作物长势遥感监测与产量预测、农业土地资源遥感等方面对中国农业遥感科研与应用进行了总结综述。 相似文献
134.
Is the long-term variation of the estimated GPS differential code biases associated with ionospheric variability? 总被引:1,自引:0,他引:1
The global positioning system (GPS) differential code biases (DCB) provided by the International GNSS Service (IGS) show solar-cycle-like variation during 2002–2013. This study is to examine whether this variation of the GPS DCBs is associated with ionospheric variability. The GPS observations from low earth orbit (LEO) satellites including CHAMP, GRACE and Jason-1 are used to address this issue. The GPS DCBs estimated from the LEO-based observations at different orbit altitudes show a similar tendency as the IGS DCBs. However, this solar-cycle-like dependency is eliminated when the DCBs of 13 continuously operating GPS satellites are constrained to zero-mean. Our results thus revealed that ionospheric variation is not responsible for the long-term variation of the GPS DCBs. Instead, it is attributed to the GPS satellite replacement with different satellite types and the zero-mean condition imposed on all satellite DCBs. 相似文献
135.
侯家窑遗址位于泥河湾盆地西北部,自发现至今,历经40余年,但遗址年代和古人类生存环境问题仍悬而未决。本文基于地质地貌观测、电阻率测深、高程测量等工作,试图通过遗址区地层结构和古河流发育情况研究,阐释上述问题。结果如下:①伴随着泥河湾古湖的快速萎缩,在侯家窑遗址区发育了一条源自北部熊耳山、宽逾1 km的古河流。它形成于240 ka B.P.前,消亡于晚更新世初,发育历史贯穿了侯家窑古人类生存阶段的始终。②遗址古文化遗存不是埋藏在湖相泥河湾层中,而是埋藏于距今约224~161 ka的牛轭湖沉积层和壤化黏土层内,表明古人类在此倚河而居长达6万年。③遗址区面向东南的宽阔圈椅状地形,为古人类生存造就了相对温和舒适的地理环境;古河流既为古人类提供了水源,良好的流域生态环境也给古人类提供了富足的食物;熊耳山既是古河流源地,也是优质石料产地,古河流将石料搬运至遗址附近,石器制作便利。因此,在寒冷气候条件下生活的古人类,选择生境较好的侯家窑遗址区倚河而居势成必然。④遗址区古河流发育在易遭侵蚀的泥河湾湖相沉积层之上,河水泥沙含量高、浑浊,唯有遗址附近的牛轭湖区水流缓滞、清澈,而且植物繁茂,是各类动物优先猎食和饮水的地方。但牛轭湖独特的地貌特点,使动物们在急迫情况下难以逃脱,古人类此地围猎,远较他地成功率高。 相似文献
136.
137.
天山南麓库车晚新生代褶皱-冲断带 总被引:2,自引:1,他引:1
库车褶皱冲断带位于天山南麓,由近东西走向的多条构造带组成。三叠系暗色泥岩、侏罗系煤层、古近系库姆格列木组膏盐层和新近系吉迪克组膏盐层构成库车褶皱冲断带的区域性主滑脱面。褶皱冲断带底面由北向南逐渐抬高。褶皱冲断带主体发育盖层滑脱-冲断构造(薄皮构造),基底卷入型冲断构造(厚皮构造)见于北缘的根带。新生界膏盐层之上构造变形以滑脱褶皱为特色,之下以冲断构造为特色。库车褶皱冲断带是印度-亚洲碰撞远程效应下,(南)天山晚新生代造山过程的产物。褶皱冲断带构造变形的动力来源主要是造山楔向塔里木盆地推进所形成的挤压构造应力。褶皱冲断带构造变形的起始时间为约23Ma,构造变形具有阶段式加速的特点,已经识别出约23Ma、约10Ma、5~2Ma和1~0Ma共4个变形加速期。褶皱冲断带的演化过程为前展式,褶皱冲断带前锋向南推进的同时,后缘持续变形。 相似文献
138.
CHENG Xiaogan LIN Xiubin WU Lei CHEN Hanlin XIAO Ancheng GONG Junfeng ZHANG Fengqi YANG Shufeng 《《地质学报》英文版》2016,90(3):870-883
Determining the spatio-temporal distribution of the deformation tied to the India-Eurasian convergence and the impact of pre-existing weaknesses on the Cenozoic crustal deformation is significant for understanding how the convergence between India and Eurasia contributed to the development of the Tibetan Plateau. The exhumation history of the northeastern Tibetan Plateau was addressed in this research using a new apatite fission track (AFT) study in the North Qaidam thrust belt (NQTB). Three granite samples collected from the Qaidam Shan pluton in the north tied to the Qaidam Shan thrust, with AFT ages clustering in the Eocene to Miocene. The other thirteen samples obtained from the Luliang Shan and Yuka plutons in the south related to the Luliang Shan thrust and they have showed predominantly the Cretaceous AFT ages. Related thermal history modeling based on grain ages and track lengths indicates rapid cooling events during the Eocene-early Oligocene and since late Miocene within the Qaidam Shan, in contrast to those in the Cretaceous and since the Oligocene-Miocene in the Luliang Shan and Yuka region. The results, combined with published the Cretaceous thermochronological ages in the Qaidam Shan region, suggest that the NQTB had undergo rapid exhumation during the accretions along the southern Asian Andean-type margin prior to the India-Eurasian collision. The Cenozoic deformation initially took place in the North Qaidam thrust belt by the Eocene, which is consistent with the recent claim that the deformation of the northeastern Tibetan Plateau initiated in the Eocene as a response to continental collision between India and Eurasia. The immediate deformation responding to the collision is tentatively attributed to the pre-existing weaknesses of the lithosphere, and therefore the deformation of the northeastern Tibetan Plateau should be regarded as a boundary-condition-dependent process. 相似文献
139.
A Survey of the Spatio-Temporal Data Model 总被引:1,自引:0,他引:1
Traditional GIS(Geographic Information System)mostly can only describe the transient state data and does not have the ability to deal with the temporal dynamic data. When the data changes, new data will take the place of the old data, namely the transient state change into another, and the old data will disappear. Therefore, it is unable to make an analysis of the updating changes of the data and predict the development trend of the future. In this case, TGIS (Temporal Geographic Information System) emerges and expands the time dimension on the basis of traditional GIS. Spatio-temporal data model is the key to TGIS. Spatio-temporal data modeling is not only related to dynamic expression of spatio-temporal objects, but also gives an important support for spatio-temporal analysis and reasoning. This paper summarized the theories and applications status at home and abroad of spatio-temporal data model in detail, illustrated family tree of spatio-temporal data model for the nearly fifty years, discussed improvement and application status of Base State with Amendments Model, Event-based Spatio-temporal Data Model, Object-oriented Data Model and other spatio-temporal data models, and raised the existing problems of spatio-temporal data model. The current existing problems mainly includes: ①There are a lot of spatio-temporal data models put forward, but some of them only focus on semantic design and neglect the verified; ②Most of existing spatio-temporal data model are for vector data, only the Event-based Spatio-temporal Data Model is raster data structure; ③At present, the expression the time-space information of geographic entity is relative separated with spatio-temporal data model; ④Spatio-temporal data model is mainly used in cadastral management, land use and forestry data updating, less application in other fields. In the end, the future development direction was put forward of spatio-temporal data model. In the time of big data and “Internet plus”, it is necessary to explore the big data spatio-temporal data model that supports multiple data formats. 相似文献
140.
通过对北京平原北部昌平、顺义、朝阳等区域的多个深孔资料、尤其后沙峪地区G3钻孔资料的深入分析,并开展磁性地层学及孢粉测试成果研究,建立了钻孔的磁性地层序列,结合南口—孙河断裂、顺义断裂以及黄庄—高丽营断裂的活动性研究成果,确定了后沙峪凹陷的第四纪地层格架,分析了凹陷的构造演化过程。结果表明,后沙峪凹陷上G3孔下更新统底界为511.7 m,中更新统底界为175.5 m,上更新统底界为31.6 m。在燕山期晚期,黄庄—高丽营断裂形成,控制了北京凹陷的西部边界,在北东向顺义断裂和北西向南口—孙河断裂共同作用下形成后沙峪凹陷。进入第四纪后,G3钻孔地层在早、中、晚更新世的沉积速率分别为0.198 mm/a、0.255 mm/a和0.243 mm/a;各条断裂活动速率的差异性客观反映出各块体之间的升降特点。由于后沙峪凹陷处于黄庄—高丽营断裂的上盘,同时也是顺义断裂的下盘,因此,断裂间的相互运动在第四纪沉积作用下形成了后沙峪凹陷。 相似文献