国家地理空间信息基准框架工程建设

提出了国家地理空间信息基准框架内改进与更新原有的大地坐标基准、高程基准和重力基准的建设道路及解决原则。     

综合EGM2008模型和SRTM/DTM2006.0剩余地形模型的GPS高程转换方法

利用SRTM以及DTM2006.0全球地形模型构建剩余地形模型（RTM）数据,并将其转换为RTM高程异常。通过GPS/水准点的优化选择法,选择少量GPS/水准点的实测高程异常,扣除EGM2008模型以及SRTM与DTM2006.0模型求得的剩余模型高程异常,对残余高程异常进行拟合,从而进一步提高GPS高程转换的精度。最...     

样条函数拟合GPS高程探讨

主要讨论了运用三次样条函数曲线拟合法来拟合GPS点的高程,并与多项式曲线拟合法比较,通过实例验证了此方法的可行性及其所能达到的精度,得出了一些有益的结论,并给出了一些建议。     

茂名城区GPS拟合高程精度的探讨

GPS控制网在联测水准点的基础上,利用GPS水准高程来实现GPS网点的大地高向正常高转换,其精度主要受所拟合的似大地水准面、已知点高程和GPS网点大地高3种误差的影响。     

GPS高程异常拟合精度的探讨

GPS技术在测量领域已广泛应用,但GPS拟合高程精度制约了其在领域内的推广普及。选择不同的高程异常拟合模型,对GPS高程拟合精度非常重要。通过对驿城区城市控制网进行不同数学模型的GPS高程异常拟合,验证了选择合适的拟合模型及分布合理的高精度水准点,能够解算出高精度的GPS拟合高程,满足一般测量工程的需要。     

Two different methods of geoidal height determinations using a spherical harmonic representation of the geopotential, topographic corrections and the height anomaly–geoidal height difference

 It is suggested that a spherical harmonic representation of the geoidal heights using global Earth gravity models (EGM) might be accurate enough for many applications, although we know that some short-wavelength signals are missing in a potential coefficient model. A `direct' method of geoidal height determination from a global Earth gravity model coefficient alone and an `indirect' approach of geoidal height determination through height anomaly computed from a global gravity model are investigated. In both methods, suitable correction terms are applied. The results of computations in two test areas show that the direct and indirect approaches of geoid height determination yield good agreement with the classical gravimetric geoidal heights which are determined from Stokes' formula. Surprisingly, the results of the indirect method of geoidal height determination yield better agreement with the global positioning system (GPS)-levelling derived geoid heights, which are used to demonstrate such improvements, than the results of gravimetric geoid heights at to the same GPS stations. It has been demonstrated that the application of correction terms in both methods improves the agreement of geoidal heights at GPS-levelling stations. It is also found that the correction terms in the direct method of geoidal height determination are mostly similar to the correction terms used for the indirect determination of geoidal heights from height anomalies. Received: 26 July 2001 / Accepted: 21 February 2002     

高精度推求正高的两种方法

论述了高精度推求正高的两种方法,并对正高精度的推估及其在模型上的试算也作了讨论,对于海拔为5000m的高山,正高的误差一般不超过±10cm,这与距青岛水准原点达数千公里的西部高山(原)处正常高的精度也比较接近。     

平坦地区转换GPS高程的混合转换方法

简要介绍了转换GPS高程的二次曲面拟合法和神经网络方法。然而 ,这 2种方法都有缺点 ,介绍的CF&NNM方法充分利用了 2者的优点 ,通过 2个平坦地区的工程实例 ,证实该方法的有效性 ,并得到一些有工程应用价值的结论。     

A novel approach to estimate canopy height using ICESat/GLAS data: A case study in the New Forest National Park,UK

The Geoscience Laser Altimeter System (GLAS) aboard Ice, Cloud and land Elevation Satellite (ICESat) is a spaceborne LiDAR sensor. It is the first LiDAR instrument which can digitize the backscattered waveform and offer near global coverage. Among others, scientific objectives of the mission include precise measurement of vegetation canopy heights. Existing approaches of waveform processing for canopy height estimation suggest Gaussian decomposition of the waveform which has the limitation to properly characterize significant peaks and results in discrepant information. Moreover, in most cases, Digital Terrain Models (DTMs) are required for canopy height estimation. This paper presents a new automated method of GLAS waveform processing for extracting vegetation canopy height in the absence of a DTM. Canopy heights retrieved from GLAS waveforms were validated with field measured heights. The newly proposed method was able to explain 79% of variation in canopy heights with an RMSE of 3.18 m, in the study area. The unexplained variation in canopy heights retrieved from GLAS data can be due to errors introduced by footprint eccentricity, decay of energy between emitted and received signals, uncertainty in the field measurements and limited number of sampled footprints.Results achieved with the newly proposed method were encouraging and demonstrated its potential of processing full-waveform LiDAR data for estimating forest canopy height. The study also had implications on future full-waveform spaceborne missions and their utility in vegetation studies.     

基于比例整体最小二乘的GPS高程拟合

针对GPS高程拟合过程中GPS基线观测量和水准高程观测量含有误差且残差中误差不相同的情况,在整体最小二乘(TLS)基础上引入比例因子λ来确定残差中误差的大小,即比例整体最小二乘(STLS)。实例计算表明,STLS比TLS和LS能够得到更好的估计参数,高程异常值拟合精度也相应提高。