我国北斗三号卫星导航系统(简称北斗三号,BDS-3)具备全球服务能力,研究北斗三号的海外应用性能,有助于北斗三号在“一带一路”沿线国家的应用推广。本文首次将北斗三号应用于非洲赤道几内亚某工程测量控制网,该控制网采用点连式E级网观测策略,包含5个观测时段、11个控制点,每个时段的平均基线长度为3.67～6.25 km。使用国产接收机、国产基线解算软件和国产平差软件的数据处理结果表明:①在赤道几内亚,可观测到的北斗三号数量为8～10颗;②使用北斗三号的基线解算、三维无约束平差、二维平面约束平差,整体精度优于GPS;③使用北斗三号得到的控制点二维平面坐标,与GPS的差异不超过1.09 cm。本文验证了北斗三号在非洲地区具备与GPS相当的控制测量应用性能。对于北斗三号控制测量应用走向全球,提供了参考。

研究南水北调中线水源区植被时空分布和演化特征,对水源区生态环境保护与社会经济长期稳定发展具有重要意义。利用2010—2019年南水北调中线水源区中分辨率成像光谱仪(MODIS)归一化植被指数(NDVI)数据,基于NDVI最大值合成和一元线性回归方法研究水源区植被时空演化特征,并结合水源区地表温度、降水与土壤湿度等数据探讨植被变化原因。结果表明:①水源区NDVI空间分布与地形强相关,2010—2019年,水源区NDVI均值为整体上升趋势;②2013—2015年水源区NDVI呈现显著的“下降-恢复”特征,可能与2014年水源区地表温度和降水异常导致的旱情、2015年水源区降水恢复以及丹江口水库蓄水水位上升有关;③2010—2019年,水源区植被发生显著变化的区域主要集中在低海拔的人口密集区,反映这些地区的植被更易受气候变化、城镇扩张和“退耕还林、植树造林”政策的影响。此外,南水北调中线工程通水后,丹江口水库水位上升是导致水库区域NDVI降低的原因。研究结果可为南水北调中线水源区生态环境保护提供科学依据。

The spatio-temporal evolution of vegetation in the water source area of the middle route project of South-to-North Water Diversion is researched via data processing and analysis using ArcMap software and Unary Linear Regression Model based on the Moderate-resolution Imaging Spectroradiometer (MODIS) Normalized Difference Vegetation Index (NDVI) data in 2010—2019.The causes of vegetation change are also discussed in association with the data of surface temperature,precipitation and soil humidity in the water source area.Results manifest that (1) the distribution of NDVI in the source area is strongly correlated with terrain.From 2010 to 2019,the mean value of NDVI displayed a steady upward trend.(2) From 2013 to 2015,NDVI showed a notable decrease-recovery trend,which is possibly related to the extreme drought due to land surface temperature and precipitation anomalies in 2014,the restoration of precipitation and the increase in the water level of Danjiangkou Reservoir in 2015.(3) From 2010 to 2019,the areas with significant changes in NDVI mainly concentrated in low-altitude densely populated areas,indicating that the vegetation in these areas is more susceptible to climate change,urban expansion and the policy of “farm land returning to woodland and planting trees”.In addition,the rising of the water level of Danjiangkou Reservoir after the running of middle route project led to the reduction of NDVI in the reservoir area.The research findings offer scientific basis for the restoration and protection of natural vegetation in the water source area of the Middle Route Project of South-to-North water diversion.

南水北调中线工程作为我国特大型线性输水建筑物,保障干渠的安全运营是推进受水区人民生活与经济发展水平的重要措施。利用改进的SBAS InSAR技术,对覆盖南水北调中线辉县段干渠自2015-04-11至2019-03-09的90景Sentinel-1A数据进行高精度处理,得到2015年4月至2019年3月期间辉县段及其周围的形变信息。结果表明:辉县段沉降区域主要分布在辉县市市中心的西南区域和峪河镇的北部区域,干渠基本处于稳定的状态,没有大尺度的沉降漏斗,沿线仅分布着一些小范围的沉降区。结合膨胀土的特性、降雨量和土壤湿度影响因子,进一步对辉县膨胀土渠段进行综合研究,结果表明,辉县膨胀土渠段呈现周期性沉降趋势,并且沉降与降雨量和土壤湿度呈现高相关性。

The Central Line Project of South-to-North Water Transfer is a large-scale linear water conveyance building in China. To guarantee the safe operation of main canals is an important measure to promote people's livelihood and economic development in water-receiving areas. In this paper, the improved SBAS InSAR technology was used to process the 90-view Sentinel-1A data covering the main canal of Huixian segment of the Central Line of South-to-North Water Transfer from April 11, 2015 to March 09, 2019. The deformation information of the Huixian segment and its surroundings in the aforementioned time period was obtained. The settlement of Huixian segment mainly distributed in the southwestern area of the city center of Huixian and the northern area of Luohe Town, while the main canals were basically stable with no large-scale settlement funnel and only a few small settlement areas along the line. The expansive soil segment of Huixian County canal was further investigated comprehensively in consideration of expansive soil characteristics, rainfall, and soil moisture. Result demonstrated a periodic settlement trend, and the settlement was highly correlated with rainfall and soil moisture.