我国大地坐标系的换代问题

首先指出了我国现有大地坐标系在先进性和实用性方面存在的问题，提出了我们面临的选择与采用地心坐标系的建议，然后就地心坐标系的定义和实现、参考椭球常数、正常重力公式等问题提出了初步意见，并就坐标系改变对旧地形图的影响问题进行了研究。我国大地坐标系应由局部坐标系更新为地心坐标系。我国大地坐标系的定义应与IERS(国际地球自转服务)协议相一致，采用国际常用的参考椭球和正常重力公式。本文提出的参考椭球和正常重力公式符合这些原则，提出的地形图坐标系变化改正方案应是基本可行的。     

航天摄影测量学的崛起

本文提出一个新学科航天摄影测量学。自飞机问世后,航空遥感摄影技术与测量学的结合,产生了航空摄影测量学,航天遥感发展的今天与摄影测量学相结合必将产生航天摄影测量学。陆地卫星获取了大量图象,具备了测制中、小比例尺地图。本文介绍从卫星轨道上获取任意时刻卫星坐标的公式,确定象片的外方位元素。在不同轨道上摄取立体象对,用空间后方交会建立立体模型,实行相对定向、绝对定向和测绘地形图的方法。     

Characteristics and landcover of estuarine boundaries: implications for the delineation of the South African estuarine functional zone

This study investigated whether the current lateral boundary for estuaries in South Africa, i.e. the estuarine functional zone (EFZ), includes all estuarine habitats. The EFZ covers 173 930 ha in 304 estuaries/outlets nationally. Field surveys and analysis of available aerial images showed that 82 (12 956.70 ha) of these estuaries (26%) had estuarine habitats occurring outside of this boundary. As a result of mapping scale, the National Vegetation Map does not represent habitats that are associated with small estuaries (approximately 50% of South Africa's estuaries). For estuaries in the Western and Eastern Cape provinces, most habitats have been lost due to urban development, whereas in subtropical areas (northern Eastern Cape and KwaZulu-Natal), cultivation has removed estuarine habitat. Although delineation of boundaries can be complicated by landcover changes, the estuarine lateral boundary in Cape estuaries could be identified based on sediment characteristics (moisture content, organic content, electrical conductivity), groundwater characteristics (salinity, conductivity and depth) and plant species. The delineation of the EFZ needs to be consistent, inclusive of all estuarine physical and biological processes, and cost-effective to identify so that it can protect estuarine habitats.     

我国数字地理空间框架建设的形势与任务

数字地理空间框架建设是构建数字中国的重要基础性工作,是测绘部门面临的紧迫任务。本文总结了"十一五"以来数字地理空间框架建设取得的主要进展,分析了存在的主要问题和面临的机遇挑战,研究提出了下一步数字地理空间框架建设的基本思路、主要任务和对策措施。     

Topographical relief characteristics and its impact on population and economy: A case study of the mountainous area in western Henan,China

Topographical relief is a key factor that limits population distribution and economic development in mountainous areas. The limitation is especially apparent in the mountain-plain transition zone. Taking the transition zone between the Qinling Mountains and the North China Plain (i.e. the mountainous area in western Henan Province) as an example and based on the 200-m resolution DEM data, we used the mean change-point analysis to determine the optimal statistical unit for topographical relief, and thereafter extracted the relief degree. Taking the 1:100,000 land use data, township population and county-level industrial data, population and economic spatial models were constructed, and 200-m resolution grid population and economic density maps were generated. Afterwards, statistical analysis was carried out to quantitatively reveal the impact of topographical relief on population and economy. In addition, the impacts of other topographical factors were discussed. The results showed the following. (1) The relief degree in western Henan is generally low, where 58.6% of the regional topography does not exceed half the height of a reference mountain (relative elevation ≤250 m). Spatially, the relief degree is high in the west while low in the east, and high in the middle while low in the north and south. There is a positive correlation between relief degree and elevation, and a much stronger correlation between relief degree and slope. (2) The linear fitting degree between the population and economic validation data and the corresponding simulation data are 0.943 and 0.909, respectively, indicating that the spatialized results can reflect the actual population and economic distribution. (3) The impact of topographical relief on population and economy was stronger than that of other topographical factors. The relief degree showed a good logarithmic fit relationship with population density (0.911) and economic density (0.874). Specifically, 88.65% of the population lives in areas where the topographical relief is ≤0.5 and 88.03% of the gross regional product was from areas where the relief is ≤0.3. Compared with the population distribution, the economic development showed an obvious agglomeration trend towards low relief areas.     

Automatic extraction of valley boundary from dems in the hilly Loess Plateau

1 INTRODUCTION The most remarkable topographical features in the severely eroded hilly Loess Plateau are positive (inter valley residual tablelands) and negative (valleys) landforms. They are separated by valley boundary. Topographic features above the boundary are called plateau (yuan) and narrow hillock. Below the boundary are gully walls and valley bottoms. This boundary lies along rapidly developing rills, grooves and gullies. The dynamic variation in valley boundary is indicative …     

基于CLDAS的贺兰山区5—9月降水时空分布特征及其与地形的关系分析

利用2008—2016年5—9月中国气象局陆面数据同化系统(CLDAS)格点融合分析降水资料以及降水观测资料,在对CLDAS格点降水融合资料进行验证的基础上,对贺兰山区降水时空分布特征以及与地形的关系进行了分析。结果表明：贺兰山区降水呈“东多西少、南多北少”的分布特征,贺兰山主峰偏西0.1°存在一个超过240 mm的降水高值中心,日降水量极值西侧高于东侧。8月降水量和短时强降水次数最多,11:00—18:00降水次数最多,午后到前半夜短时强降水次数最多。贺兰山区降水以小雨为主,其次是中雨,中雨和小雨雨量占区域总雨量的比例高达85%。贺兰山区降水量随海拔高度的增加而增加,西坡降水随高度的增加率为5.1 mm/hm,东坡降水随高度的增加率为2.1 mm/hm,西坡明显高于东坡。中雨日数与地形高度的相关性较好,其它级别降雨日数与地形相关性不强。     

地形对夏季冰雹事件时空分布的影响研究

从北京地区冰雹事件的时空分布特征出发,结合典型的天气个例,研究了地形热力和动力作用与强对流生成环境、降雹落区、移动方向和演变特征之间的关系。结果表明:北京地区降雹事件主要集中在北部山区,降雹时间一般出现在午后,可能与山区与平原地区之间,白天形成强烈的热力差异造成的不稳定以及由此产生的局地流场强迫有密切关系:1)在一定条件下(例如“焚风效应”等),午后山区的实际气温有可能接近甚至明显高于平原地区,为强对流天气系统在山区发展提供了更有利的热力不稳定条件;2)午后由山区指向平原的扰动温度梯度是造成低空垂直切变的强迫源。扰动温度梯度越大,低空垂直切变越强———即动力不稳定越强,因此,对流最旺盛(形成降雹)的地点往往出现在扰动温度梯度最大而不是地面气温最高的地方;3)地形热力环流和动力强迫构成的上升运动有利于强对流系统的启动。     

Environmental Impacts of Illegal Immigration on the Cleveland National Forest in California

Historical geographic information systems (GIS) scholarship has provided important insights into a broad spectrum of historical questions in recent years. This article contributes to the emerging field of historical GIS by employing map algebra and transect analysis to quantitatively assess topographical change resulting from rapid urban growth in New York City since the first quarter of the nineteenth century. These methodological techniques enable a systematic comparison of Manhattan's historical and contemporary topography through a spatial analysis of various topographic metrics, including the extent of positive and negative elevation change, shifts in elevation range, the percentage of geographic area that experienced elevation changes, and the estimated volume of Earth added to and removed from particular areas within the study site. The results indicate that there were more valleys filled than hills leveled on Manhattan's East Side, whereas the reverse was the case on the West Side. The West Side, however, experienced considerably more topographic changes than its eastern counterpart, in large part due to the former's more rugged terrain. Overall, the evidence suggests that although Manhattan's topography has been radically transformed in certain respects, the broader spatial pattern of topographic variation has remained largely constant. These findings, therefore, can be used to support competing narrative claims concerning the significance of the topographical transformations that resulted from the urbanization process in New York City.     

潮间带地形测量的新途径

潮间带,特别是宽阔的浅滩或淤泥滩地带是海洋测绘中的困难地带。本文提出用ＤＧＰＳ定位结合杆测水深的地形测量方法,代替常规水深地形测量方法,使潮间带水深地形测量变得越来越简便快速。