公路勘测中应注意的几个问题     

王生才 《测绘与空间地理信息》2006,29(6):111-112

结合营口滨海大道勘测设计工程实例,探讨了公路勘测时坐标系统选择、平面控制点点位选定、全站仪三角高程代替四等水准、RTK技术应用等一些问题,并提出了几点结论。  相似文献   

Observation on height changes of chinese tide gauges by GPS     

LIU Genyou ZHU Yaozhong XU Houze ZHANG Weimin 《地球空间信息科学学报》2006,9(4):244-249

IntroductionBecause of global temperature rising and glacierthawing,the sea level has risen about 10-25 cmin the past century[1]. The sea level change isone of the main ai ms in global change monito-ring. Presently the basic tool used in sea levelmonitori…  相似文献   

单面边坡的两种动力反应形式及其临界高度   总被引：20，自引：0，他引：20       下载免费PDF全文

祁生文 《地球物理学报》2006,49(2):518-523

把单面边坡的动力反应分为高边坡动力反应和低边坡动力反应两类. 研究了两种不同动力反应形式临界边坡高度的影响因素. 量纲分析表明弹性条件下边坡动力反应临界高度Hthre与构成边坡材料的动弹性模量Ed的平方根成正比,与边坡材料的密度ρ成反比,与边坡动力输入的特征周期T成正比. 结合弹性波动理论,利用大量数值模拟和统计分析得到了Hthre的表达式. 当边坡的高度大于Hthre时,边坡的动力反应呈现高边坡动力反应规律,当边坡的高度小于Hthre时,边坡的动力反应呈现低边坡动力反应规律.  相似文献   

Hilbert变换在海浪波高与周期联合分布函数中的应用     

李响  李海  张蕴斐  徐德伦  吴辉碇 《海洋预报》2006,23(3):1-13

Longuet-Higgins(1983)[1]导出了波高与周期的联合分布函数,此分布函数虽然与实际数据符合良好,但存在很大的缺陷,如:由此分布函数得出的波高分布为形式较为复杂的非Rayleigh分布,很难应用于工程计算中。孙孚(1988a)[2]应用射线理论导出了一种波高与周期联合分布,虽然弥补了Longuet-Higgins的一些缺陷,但推导过程过于复杂。本文在窄谱假定下通过应用Hilbert变换方法得出新的分布函数并与前两者比较,表明Hilbert变换的方法不但简便,而且完全克服Longuet-Higgins的不足,可以方便的应用于工程计算中。本文也为Hilbert变换的方法在工程中的应用提供了理论依据。  相似文献   

植被覆盖、放牧和季节对牧草种类组成和生物量的影响:以埃塞俄比亚南部Yabello牧场为例     

Yeneayehu FENETAHUN  徐新文  尤源  王永东 《资源与生态学报(英文版)》2020,11(2):159-170

Yabello牧场是埃塞俄比亚博拉纳的一个半干旱地区的牧场,目前面临着草场退化的严重挑战。植被覆盖的变化、过度放牧和季节性变化极大地影响了Yabello牧场的牧草组成和生物量。本文评估了植被覆盖、放牧和季节对Yabello牧场的牧草组成和生物量的影响。首先采用1 m×1 m的随机样方进行实验,根据植被覆盖类型和放牧变化选择样点,并对季节影响进行评估。使用SAS统计软件和MicrosoftExcel分析牧草组成、牧草高度和质量数据。本研究总共记录了26种草种,其中Chloris roxburghiana, Chrysopogon aucheri和Chrysopogon aucheri草种均表现出最高的平均单种覆盖高度和生物量产量。因此,建议将这些草种用于研究区域退化草地的恢复。研究结果还表明,植被覆盖类型、放牧和季节变化是决定牧草种类组成、牧草高度和生物量产量的关键因素。最后,研究结论还认为控制灌木丛植被并平衡放牧水平的可持续管理对于该地区的可持续牧草生产和生物多样性保护至关重要。  相似文献   

Moving from plot-based to hillslope-scale assessments of savanna vegetation structure with long-range terrestrial laser scanning (LR-TLS)     

《International Journal of Applied Earth Observation and Geoinformation》2020

Reliable quantification of savanna vegetation structure is critical for accurate carbon accounting and biodiversity assessment under changing climate and land-use conditions. Inventories of fine-scale vegetation structural attributes are typically conducted from field-based plots or transects, while large-area monitoring relies on a combination of airborne and satellite remote sensing. Both of these approaches have their strengths and limitations, but terrestrial laser scanning (TLS) has emerged as the benchmark for vegetation structural parameterization – recording and quantifying 3D structural detail that is not possible from manual field-based or airborne/spaceborne methods. However, traditional TLS approaches suffer from similar spatial constraints as field-based inventories. Given their small areal coverage, standard TLS plots may fail to capture the heterogeneity of landscapes in which they are embedded. Here we test the potential of long-range (>2000 m) terrestrial laser scanning (LR-TLS) to provide rapid and robust assessment of savanna vegetation 3D structure at hillslope scales. We used LR-TLS to sample entire savanna hillslopes from topographic vantage points and collected coincident plot-scale (1 ha) TLS scans at increasing distances from the LR-TLS station. We merged multiple TLS scans at the plot scale to provide the reference structure, and evaluated how 3D metrics derived from LR-TLS deviated from this baseline with increasing distance. Our results show that despite diluted point density and increased beam divergence with distance, LR-TLS can reliably characterize tree height (RMSE = 0.25–1.45 m) and canopy cover (RMSE = 5.67–15.91%) at distances of up to 500 m in open savanna woodlands. When aggregated to the same sampling grain as leading spaceborne vegetation products (10–30 m), our findings show potential for LR-TLS to play a key role in constraining satellite-based structural estimates in savannas over larger areas than traditional TLS sampling can provide.  相似文献   

Inter-comparison of remote sensing platforms for height estimation of mango and avocado tree crowns     

《International Journal of Applied Earth Observation and Geoinformation》2020

To support the adoption of precision agricultural practices in horticultural tree crops, prior research has investigated the relationship between crop vigour (height, canopy density, health) as measured by remote sensing technologies, to fruit quality, yield and pruning requirements. However, few studies have compared the accuracy of different remote sensing technologies for the estimation of tree height. In this study, we evaluated the accuracy, flexibility, aerial coverage and limitations of five techniques to measure the height of two types of horticultural tree crops, mango and avocado trees. Canopy height estimates from Terrestrial Laser Scanning (TLS) were used as a reference dataset against height estimates from Airborne Laser Scanning (ALS) data, WorldView-3 (WV-3) stereo imagery, Unmanned Aerial Vehicle (UAV) based RGB and multi-spectral imagery, and field measurements. Overall, imagery obtained from the UAV platform were found to provide tree height measurement comparable to that from the TLS (R² = 0.89, RMSE = 0.19 m and rRMSE = 5.37 % for mango trees; R² = 0.81, RMSE = 0.42 m and rRMSE = 4.75 % for avocado trees), although coverage area is limited to 1–10 km² due to battery life and line-of-sight flight regulations. The ALS data also achieved reasonable accuracy for both mango and avocado trees (R² = 0.67, RMSE = 0.24 m and rRMSE = 7.39 % for mango trees; R² = 0.63, RMSE = 0.43 m and rRMSE = 5.04 % for avocado trees), providing both optimal point density and flight altitude, and therefore offers an effective platform for large areas (10 km²–100 km²). However, cost and availability of ALS data is a consideration. WV-3 stereo imagery produced the lowest accuracies for both tree crops (R² = 0.50, RMSE = 0.84 m and rRMSE = 32.64 % for mango trees; R² = 0.45, RMSE = 0.74 m and rRMSE = 8.51 % for avocado trees) when compared to other remote sensing platforms, but may still present a viable option due to cost and commercial availability when large area coverage is required. This research provides industries and growers with valuable information on how to select the most appropriate approach and the optimal parameters for each remote sensing platform to assess canopy height for mango and avocado trees.  相似文献   

利用CEEMD分析中国沿海GNSS站高程时序变化     

刘豪  周东旭  王盼龙  张化疑  王永康  姜传苓 《测绘通报》2020,(3):39-43,77

利用完备经验模态分解方法（CEEMD）对我国沿海地区6个GNSS基准站（2010—2018）的高程时序数据进行了处理分析。结果表明：CEEMD在高程时间序列分析中具有一定的优越性,可准确分解出各GNSS站高程时序中存在的周、月、季节、年等变化周期项,其中周年运动是主要贡献项,各站高程时间序列的短周期变化与潮汐变化周期具有密切关联性;沿海GNSS站的地面沉降既具有区域的一致性,又存在区域间差异性,其中D区DBJO、DZJJ站呈现先下降后上升的趋势,N区NZUH、NWZU站呈下降趋势,B区的BZMW呈上升趋势,而同海区的BLHT站则呈显著的下降趋势。  相似文献   

二次曲面与最小二乘配置的组合模型在GPS高程异常拟合中的应用     

吕建伟  张志华  张新秀  刘祖昱 《测绘通报》2020,(5):127

在工程实践应用中,为了有效利用GPS高程数据,减少对传统水准测量的依赖,提高GPS高程异常的拟合精度便显得十分重要。为此,本文在介绍二次曲面拟合和最小二乘配置拟合基本原理分析、算法过程推导的基础上,提出了一种新的高程异常拟合方法。首先在二次曲面拟合的基础上,计算得到原始观测数据与拟合数据之间的残差序列,然后采用最小二乘配置模型对包括二次曲面拟合模型误差的综合误差进行优化减弱,最后得到新的高程异常。通过实例,将二次曲面拟合法,最小二乘配置法与文中提出的新方法进行比较分析。结果表明：新的组合方法的拟合预测精度要明显优于最小二乘配置及二次曲面拟合。  相似文献   

精密单点定位结合EGM2008模型在新疆某河地质断面测量中的应用     

李玉平 《测绘与空间地理信息》2020,(1):192-195

针对新疆某河地质断面测量范围大、测区通行困难、测量部位分散、传统控制测量方法工作量大且效率低的问题,在测区每条断面上布设断面基点作为控制点并用GNSS接收机静态观测(无需同步),选用武汉大学开发的Trip2.0软件加载事后精密星历和精密钟差等信息解算静态观测数据得到ITRF框架下的三维坐标,然后采用TBC软件加载EGM2008超高阶地球重力场模型点校正得到控制点的国家平面坐标和正常高。结果表明,Trip2.0软件计算的三维点位中误差最大为0.066 m,点校正坐标转换残差与已知点差值均满足限差要求;该方法平面控制测量工作量比传统方案减少46%,五等水准测量比传统方案减少98%,节约工期约56%。实践表明,采用该方法可快速地实现测区面积大、测点分散、控制点稀少区域的平面及高程控制测量。  相似文献