Systematic errors in levelings of mountainous areas

Sources of errors in the precise leveling influencing the results of measurements especially strongly in mountains are considered in this study. Data are given on new error sources, including (1) the difference in temperatures of invar bands of rods and of the air; and (2) displacements of rock bench marks during diurnal variations in temperature of rocks. The ranges of possible total systematic error in leveding are estimated.     

补偿最小二乘估计在确定高程异常中的应用

针对常规最小二乘拟合求解高程异常存在的模型误差,本文提出将模型误差看作非参数信号采用补偿最小二乘法来处理,讨论了正则化矩阵R和平滑参数α的选取对拟合结果的影响,在对各种求解光滑参数深入研究的基础上,提出了一种Xu(α)函数法,并对一个测区的GPS水准数据进行解算,结果表明,利用补偿最小二乘模型求解高程异常优于最小二乘法。     

小区域GNSS高程异常拟合方法研究

选取恰当的拟合模型是提高高程异常拟合精度的关键．本文利用湖南省新化县城区全球卫星导航系统（GNSS）和水准测量数据,采用反距离加权法、多项式插值法、径向基函数法、克里金插值法等多种曲面拟合方法进行高程异常拟合研究,并进行拟合精度评定．结果表明,径向基函数插值法内插精度最高,其中误差为±0.0158 m;局部多项式插值法外推精度最高,其中误差为±0.0104 m;综合来说,局部多项式插值法在县域尺度高程拟合中精度最高,本文研究结果对小区域GNSS高程拟合方法选取工作具有一定的参考意义.      

Harmonic continuation and gridding effects on geoid height prediction

Least-squares collocation and Stokes integral formula, as implemented using the Fast Fourier Technique, handle the harmonic downward continuation problem quite differently. FFT furthermore requires gridded data, amplifying the difference of methods.We have in this paper studied numerically the effects of downward continuation and gridding in a mountainous area in central Norway. Topographically smoothed data were used in order to reduce these effects. Despite the smoothing, it was found that the vertical gravity gradient had values up to -11 mgal/km. The corresponding differences between geoid heights and the height anomalies at altitude reached 12 cm.The differences between geoid heights obtained using collocation or FFT with gravity data at terrain level or sea level showed differences between the values of up to 10 cm r.m.s. A part of this difference was a consequence of different data areas used in the FFT and collocation solution, though.Major discrepancies between the solutions were found in areas where the topographic smoothing could not be applied (deep fjords with no depth information in the used DTM) or where there seemed to be gross errors in the data.We conclude that proper handling of harmonic continuation is important, even when we as here have used a 1 km resolution DTM for the calculation of topographic effects. The effect of data gridding, required for the FFT method, seems not to be as serious as the need to limit the data distribution area, required when least squares collocation is used with randomly distributed data.     

改进多面函数拟合跨带区域高程异常的研究

针对跨带区域高程异常拟合中存在的问题,该文以多面函数模型为背景,分别采用直接法和分带法,提出采用大地坐标(B,L)作为核函数参数的改进多面函数模型,对跨带区域高程异常进行拟合。通过某跨带区域GPS水准网数据验证,结果显现了改进后多面函数模型在跨带区域拟合上的优势,其外符合精度相比其他函数模型有显著提高。     

河口海岸区GPS高程异常的空间特征与拟合研究

为了实现河口海岸区GPS大地高向正常高的转换,就需要掌握该区高程异常的空间特征并进行高精度的拟合研究.文章以福建闽江口为研究区,综合应用半方差函数以及整体和局部逼近拟合方法对闽江口测区GPS高程异常进行研究.结果表明:闽江口GPS高程异常在空间上可用高斯和球状半方差函数进行表达,水平分布上呈海区至陆地逐渐变小的分带规律性;二次曲面和Shepard分区加权方法对研究区高程异常的整体拟合和局部逼近结果具有相似的累积频率分布和外符合精度,而两者的组合模型较之单一拟合方法在精度上提高42.9％～55.2％,可获得较为稳健的拟合结果,适用于该地形条件复杂的河口海岸区.     

基于钟差预测的铯原子钟频率异常检测算法及性能分析

提出一种基于钟差预测的铯原子钟频率异常检测算法.将钟差预测不确定度的解析表达式作为理论依据,以预测误差作为检验统计量,对检验统计量做二元假设检验.在两种情况下,检验统计量都服从正态分布.通过约束虚警概率(PFA),查询正态分布的分布函数,得到对应的检测门限值.根据在异常情况下的检验统计量分布函数和检测门限值,推导给出了...     

倾斜摄影技术在丘陵山区大比例尺测图中的应用

针对丘陵山区大比例尺测图应用的需求,本文探讨了如何通过倾斜摄影的技术方法获取高精度的影像模型.首先通过分析航线布设方法、控制点布设采集要点、空三数据处理关键点等,获取满足丘陵山区大比例尺测图应用的数据模型,基于数据模型获取大比例尺地形图数据;然后通过与实地测量数据进行精度对比分析获取试验结果,结果表明倾斜摄影技术不但能...     

The geodetic approximations in the conversion of geoid height to gravity anomaly by Fourier transform

Six sources of error in the use of Fourier methods for the conversion of geoid heights to gravity anomalies are considered. The errors due to spherical approximation are unimportant. The errors due to approximations in Stokes' integral may be eliminated by use of the gravity coating rather than the gravity anomaly. The chord-to-arc error and the truncation error may be reduced by using a reference field. Tapering of the edges of the measurement window reduces the truncation error. The long-wavelength components of the high degree spherical harmonics cause small offsets in the resulting gravity anomalies. The errors due to the plane approximation can be reduced by appropriate choice of map projection and area of integration.     

深度学习支持下的丘陵山区耕地高分辨率遥感信息分区分层提取方法

耕地是丘陵山区稀缺的土地资源,具有地形条件复杂、种植结构多样的特点,导致了山地耕地信息难以快速、准确获取,并且基于传统的遥感数据及遥感监测方法开展山区耕地信息快速自动提取比较困难。针对这一问题,本文以西南山区贵州省息烽县作为试验区,根据地理空间异质性特征,提出分区控制、分层提取的耕地形态信息提取思路,构建了一种地貌单元约束条件下的分区分层耕地形态信息的提取方法。该方法首先根据地貌-植被特征将试验区划分为平坝区、山坡区、林草区3类地理分区;然后在每类分区基础上,根据耕地所呈现的视觉特征划分为不同的类型,对不同类型的耕地分别设计不同的深度学习模型进行分层提取。试验结果证明,该方法对山区复杂地形背景噪声具有较好的抑制作用,所提取的耕地地块信息相比于传统方法更符合实际耕地的实际分布形态,有效地减少了漏提率和错提率。     

机载激光雷达在密林山区测绘中的应用

机载激光雷达是近年来发展迅速的高新测绘技术,具有机动性高、数据覆盖量大、作业效率高和精度可靠等特点。针对当前山区沟壑且有大量植被覆盖区域进行传统测量作业较为困难,危险性大的问题,采用机载激光雷达技术获取研究区原始点云数据,在此基础上,对比分析四种滤波算法的点云分类效果,得到适用于密林沟壑区的点云滤波方法,进而通过人机交互和地面点内插实现了测区高精度数字高程模型（digital elevation model,DEM）的构建,最终获得的DEM高程中误差为0.09 m,满足实际测绘生产需求,生产效率大大提高。研究结果表明,机载激光雷达技术应用于复杂危险地形测绘具有极大优势。     

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

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。     

单基站GPS差分系统在山区线路测量中的应用探讨

RTK技术的出现,使得野外实时测量精度达到厘米级,RTK测量具有实时性好、精度高、速度快等优点,是常规测量所无法比拟的,RTK已经作为快速采集数据与定位的有效工具。本文比较分析了常规RTK系统和网络RTK的优缺点,并详细介绍了单基站GPS差分系统的特点,并在实际工程应用中对其精度和有效距离进行了探讨。     

机载LiDAR技术应用于茂密植被山区地质灾害调查

我国茂密植被山区地质灾害具有高位、高隐蔽性的特点,传统地质灾害排查手段在有效解决隐患的早期识别方面存在一定困难.机载雷达技术不仅可获取地面反射的三维激光点云,同时能够提供高分辨率、高精度的地形地貌二维影像.机载雷达的多次回波技术可"穿透"地面植被,通过滤波算法能够有效去除地表植被的影响,获取真地面高程数据信息,从而可获...     

Tropospheric delay gradients from numerical weather prediction models: effects on GPS estimated parameters

Several numerical weather prediction (NWP) models provide information on the 3D state of the neutral atmosphere which has enabled GNSS researchers to have improved a priori information of the delay induced in the GNSS signals. However, the quality of weather models on the one hand and computational difficulties on the other, are motivations to develop an algorithm based partly on NWP models, while still estimating the remaining residual delay through GNSS processing strategies. An algorithm has been developed to estimate horizontal delay gradients from Meteorological Service of Canada NWP models. The GNSS software “Bernese” has also been modified to handle these gradients, as well as zenith delay and mapping functions based on NWP models in phase and code observation equations. Month-long precise point positioning results show strong correlation between north–south hydrostatic gradients and latitude differences, with significant but less strong correlation with the height and zenith total delay parameters. The longitude components were not sensitive to the implementation of gradients. High precision GNSS applications such as long term geodynamics studies, realization of terrestrial reference frames and climatology and consequential interpretations may be affected by ignoring the asymmetry of the neutral atmosphere. In addition to estimating the gradients, implementing a priori information on gradients in the processing software may have an impact on estimated results and consequential interpretations.     

驱动山区农业产业遥感监测的GMG协同系统建设与应用

由于喀斯特山区地貌的支离破碎、地形的高低起伏及气候的多云与雾,难以通过常规遥感手段实现大范围农作物的快速监测,针对该情况,本文研发了内外业一体化的GMG协同系统。该系统利用GPS的精准定位、多媒体的丰富语义及GIS的数据处理优势,多向驱动贵州山区农业产业遥感监测。实践表明,该系统快速实现了省域监测中解译样本的多样性,有效弥补了局部区域内遥感监测的局限性,同时检验了解译数据的准确性。     

A numerical study of the divergence of spherical harmonic series of the gravity and height anomalies at the earth's surface

The problem of the divergence of the geopotential spherical harmonic series at the earth's surface is investigated from a numerical, rather than a theoretical, approach. A representative model of the earth's potential is devised on the basis of a density layer, which, in the spherical approximation, generates a gravity field whose harmonic constituents decay according to an accepted degree variance model. This field, expanded to degree 300, and a topographic surface specified to a corresponding resolution of 67 km are used to compute the differences between truncated inner and outer series of the gravity and height anomalies at the surface of the earth model. Up to degree 300, these differences attain RMS values from 0.33 μgal to 86 μgal for the gravity anomaly and from 0.32 μm to 410 μm for the height anomaly, in areas ranging respectively from near the equator to the vicinity of the pole. In addition to these values, there is an expected truncation effect, caused by the neglect of higher degree components of the inner series, of about 30 mgal and 36 cm, respectively. The field is then subjected to a Gaussian filter which effectively cuts off information at degree 300 (at the 5% level). The RMS error to degree 300 is thereby reduced by factors of 10 to 20, with a concomitant reduction in the truncation effect to about 0.3 mgal and 0.7 cm.     

基于光谱和纹理特征的山区高分辨率遥感影像分类

本文在只做阴影补偿而不做地形校正的情况下,使用光谱和纹理特征相结合的方法进行山区高分辨率遥感影像分类。实验取得了78%的分类精度,表明该方法合理可行,具有一定的实用性。