共查询到20条相似文献，搜索用时 31 毫秒
1.
《测量评论》2013,45(82):177-184
AbstractA method of applying azimuth control to a survey is given in which the precision with which the astronomical position must be determined is proportional to tan (altitude) instead of tan (latitude) as in the orthodox method. By using the method with stars of low altitude the observational difficulties are greatly reduced, especially in high latitudes. Methods of observation and reduction are discussed which make it possible to avoid altogether special observations to determine the astronomical position. 相似文献
2.
针对传统时差法水位改正按距离内插计算的潮时差可能与实际情况存在较大差异，进而影响水位改正效果的问题，提出利用天文潮直接计算站间潮时差实施水位改正的方法，研究了我国沿海部分验潮站天文潮与实测水位之间潮时系统的差异与变化性质，并分析了不同分潮选择下确定的天文潮对站间潮时差计算值的影响量级。利用黄海沿岸与北部湾的验潮站设计了天文潮时差水位改正试验，比较了传统时差法与天文潮时差方法的效果。试验和分析表明，利用天文潮计算潮时差比传统时差法更接近实测潮时差，且8分潮水位改正结果的中误差控制在5 cm以内，比传统时差法的水位改正精度提高了近一倍，实现了对传统方法的改进，证明了利用天文潮进行时差法水位改正的可行性。 相似文献
3.
我国天文大地网与1980年大地坐标系的建立及应用 总被引：2，自引：0，他引：2
全面论述了我国天文大地网整体平差和１９８０年大地坐标系的建立及其应用，包括：第一，我国天文大地网的结构和参数整体平差的规模。第二，参考椭球的选择和定位，长度基准；垂线偏差和高程异常的计算；在椭球面上进行平差的问题；平差中拉普拉斯方位角的处理；各级大地网整体统一平差的问题。第三，用于我国天文大地网整体平差中的条件联系平差法的基本原理和它的几个特殊问题的处理方法；一种适用于电子计算机计算的大规模法方程 相似文献
4.
为满足新建射电望远镜在单站或多站联合进行的深空探测或射电天文观测对中心坐标精确测定的要求,提出一种利用已知精确中心坐标的望远镜作为参照物,测量地平式射电望远镜中心点坐标的方法和测量数据处理方法。这一方法对场地和设备的要求较低,能够得到毫米级或亚毫米级的位置精度。尤其适合对天线阵列的中心位置进行测量。对国家天文台密云观测站的40 m射电望远镜进行了中心坐标测量,位置均方根误差为2.312 mm,满足了后续的观测工作对其位置的需求。 相似文献
5.
6.
Erik W. Grafarend 《Journal of Geodesy》1985,59(2):124-138
Summary From a two-dimensional network adjustment it is well understood that the one orientation unknown of a theodolite frame is
estimable, once the orientation datum parameter, e.g., one azimuth, is fixed. In three-dimensional networks the problem of
estimability of three orientation unknowns inherent in a theodolite frame is more complex. Here we prove that not only the
classical horizontal orientation unknown is estimable (up to the datum degrees of freedom), but also astronomical longitude
and astronomical latitude which can be considered as two additional orientation unknowns of the theodolite frame moving with
respect to an earth-fixed equatorial frame of reference. Thus the theodolite instrument can be considered—at least theoretically—a
gradiometer measuring the variation of the directional parameters of the gravity vector from one point to another. Or up to
the datum degrees of freedom astronomical longitude and astronomical latitude can be determined from only theodolite observations
between exclusively terrestrial points. M?nicke (1982), has shown that despite the refraction problem the method works sufficiently
well in practice. 相似文献
7.
Astronomical-topographic levelling using high-precision astrogeodetic vertical deflections and digital terrain model data 总被引：2，自引：1，他引：1
At the beginning of the twenty-first century, a technological change took place in geodetic astronomy by the development of
Digital Zenith Camera Systems (DZCS). Such instruments provide vertical deflection data at an angular accuracy level of 0.̋1
and better. Recently, DZCS have been employed for the collection of dense sets of astrogeodetic vertical deflection data in
several test areas in Germany with high-resolution digital terrain model (DTM) data (10–50 m resolution) available. These
considerable advancements motivate a new analysis of the method of astronomical-topographic levelling, which uses DTM data
for the interpolation between the astrogeodetic stations. We present and analyse a least-squares collocation technique that
uses DTM data for the accurate interpolation of vertical deflection data. The combination of both data sets allows a precise
determination of the gravity field along profiles, even in regions with a rugged topography. The accuracy of the method is
studied with particular attention on the density of astrogeodetic stations. The error propagation rule of astronomical levelling
is empirically derived. It accounts for the signal omission that increases with the station spacing. In a test area located
in the German Alps, the method was successfully applied to the determination of a quasigeoid profile of 23 km length. For
a station spacing from a few 100 m to about 2 km, the accuracy of the quasigeoid was found to be about 1–2 mm, which corresponds
to a relative accuracy of about 0.05−0.1 ppm. Application examples are given, such as the local and regional validation of
gravity field models computed from gravimetric data and the economic gravity field determination in geodetically less covered
regions. 相似文献
8.
《测量评论》2013,45(79):19-24
AbstractA problem frequently encountered by surveyors in carrying out a system of triangulation, is the adjustment of a network of lower order triangulation to make it geometrically consistent with an existing triangulation of a higher order. For example, in Fig. 1 it will be assumed that the positions of the stations A, B, and C have already been determined and that it is now required to determine the positions of the stations a, b, c, d, e and f from the measured values of the internal angles of the network of triangulation shown. In practice, several different solutions have been suggested, ranging from rigorous least squares methods to semi-graphical solutions. The method described in this article is believed to be original and may prove of interest to surveyors. 相似文献
9.
Major Mark C Breach MA MSc ARICS RE 《Journal of Geodesy》1985,59(3):221-232
A method of determining azimuth by gyrotheodolite without electronic registration is described. The method requires observations
of time at each instant the moving mark passes a scale division. Thus many observations of time may be achieved in a single
oscillation of the moving mark. The observations when used in the appropriate observation equation may determine azimuth with
a standard error of ±3″ with 2 hours of observations. This assumes knowledge of the additive constant to about 1″.3 and neglects
the effects of dislevelment in the prime vertical. For practical application of the method a time recording device and microcomputer,
such as the Hewlett Packard HP41CV and HP85, are recommended. 相似文献
10.
《测量评论》2013,45(20):343-346
AbstractA GOOD deal of astronomical work was called for during the operations of the British Somaliland–Ethiopia Boundary Commission. The method employed by the British Section for the determination of local time being that of star altitudes in the prime vertical, after the first few stations had been occupied the suggestion was made that the observer could be saved considerable strain by the preparation of a programme for time observations, much on the same lines as for latitudes. The proposal was tried, proved eminently successful, and became a standard part of the British Section's procedure. An example of such a programme is given below. I t is a little laborious, but simple. 相似文献
11.
《测量评论》2013,45(30):457-462
AbstractIn the original geodetic series in Southern Rhodesia—completed by Mr Alexander Simms in 1901—the geographical coordinates of all stations were referred to the point SALISBURYas origin. The coordinates of SALISBURY were fixed by interchange of telegraphic signals with the Royal Observatory at the Cape for longitude, combined with astronomical determinations of time, latitude, and azimuth (see Vol. III, “Geodetic Survey of South Africa”). 相似文献
12.
针对GNSS三维无约束平差不依赖基准且拥有高精度几何网形的特点,以GNSS监测网作为一个整体的时空观测单元,由GNSS网测站间相互关联的所有基线长度和基线夹角变化综合衡量网形的变化,用网形的变化集中反映区域地壳形变信息。利用地壳形变高空间相关性的特点,采用主成分时空响应分析的方法实现了区域地壳形变信息的快速提取。通过对2013年芦山Ms7.0地震近场区域陆态网GPS基准站2010—2014年观测数据的解算,提取并分析了对应地震前后近场区域地壳形变时空分布特征及形变的动态演变过程。 相似文献
13.
Richard A. Snay 《Journal of Geodesy》1990,64(1):1-27
The North American Datum of 1983 (NAD 83) provides horizontal coordinates for more than 250,000 geodetic stations. These coordinates were derived by a least squares
adjustment of existing terrestrial and space-based geodetic data. For pairs of first order stations with interstation distances
between 10km and 100km, therms discrepancy between distances derived fromNAD 83 coordinates and distances derived from independentGPS data may be suitably approximated by the empirical rulee=0.008 K0.7 where e denotes therms discrepancy in meters and K denotes interstation distance in kilometers. For the same station pairs, therms discrepancy in azimuth may be approximated by the empirical rule e=0.020 K0.5. Similar formulas characterize therms discrepancies for pairs involving second and third order stations. Distance and orientation accuracies, moreover, are well
within adopted standards. While these expressions indicate that the magnitudes of relative positional accuracies depend on
station order, absolute positional accuracies are similar in magnitude for first, second, and third order stations. Adjustment
residuals reveal a few local problems with theNAD 83 coordinates and with the weights assigned to certain classes of observations. 相似文献
14.
新天文常数、系统对天文经纬度和方位角的影响 总被引：1，自引：0，他引：1
本文从理论上讨论了新天文常数、系统对恒星视位置影响的周期性、计算公式及其数值范围,并结合一等天文外业的实际情况,推导了新天文常数、系统对天文经纬度和方位角的影响公式及其数值范围,从而得出在任何年观测都可以使其影响忽略不计等结论。 相似文献
15.
《测量评论》2013,45(62):295-297
AbstractA Few notes will now be given on the subject of triangulation on which practically all the methods already outlined depend. If we have a triangulation ready for us on which to base our work, so much the better; but, if not, we must make every effort to carry one through either from our own measured base or from any existing points on the edge of our work. For reconnaissance survey, such a triangulation must be carried out with the greatest expedition; even if all refinements are sacrificed to speed, it is extraordinary how small the errors will be found to be when a more rigid triangulation is made. Any unorthodox method such as carrying through with a resected point or with an astronomical azimuth may be adopted. A bush will often make a good point to observe to, also piles of bushes with a flag on a reed or stick. 相似文献
16.
L. A. Kivioja 《Journal of Geodesy》1983,57(1-4):146-151
The theodolite used in this method is completely leveled by using autocollimation from a free mercury surface. This eliminates the need for striding or hanging levels which are in conventional use to level the trunion axis of the theodolite. Mercury leveling is more accurate and can be performed in a much shorter time than leveling by the striding or hanging levels. In addition, this new method removes the unavoidable axis wobbles contaminating the observed horizontal angles between the star and the azimuth mark. The uncontrolled wobble errors affecting azimuths can be up to three arc seconds. The axis wobbles are removed by using autocollimation from an axis mirror which is perpendicular to the trunnion axis of the theodolite. Autocollimation coincidences from the mercury and from the axis mirror can be made within one or two tenths of an arcsecond. This new method and instrumentation surpasses the obtainable precision by the conventional first-order astro azimuth observations by reducing the unknown systematic wobble and level errors by one order of magnitude. 相似文献
17.
近年来,有研究发现在GPS测站坐标时间序列中既存在白噪声,也存在有色噪声。为了研究有色噪声对东南极区域GPS测站三维速度估计的影响,本文使用GAMIT/GLOBK10.5软件对东南极区域6个连续GPS测站2005—2014年的实测数据进行解算和平差,并利用最大似然法（MLE）分别估计了在两种假设噪声模型条件下的测站三维运动速度及其不确定性。结果表明：在进行参数估计时,考虑两种有色噪声（闪烁噪声和随机游走噪声）对东南极区域GPS测站三维速度估计的量级影响不大,水平方向最大影响量级为0.3 mm/a,垂直方向最大影响量级为0.8 mm/a;但如果不考虑有色噪声,会严重低估参数估计的真实不确定性。 相似文献
18.
为了实现SAR图像区域网平差时连接点的自动稳健提取,面向相同侧视方向、近似平行轨道的异轨SAR图像,针对其方位向相对几何畸变较小、距离向相对几何畸变较大的特点,提出一种采用差异化约束的SAR图像连接点提取方法。该方法在构建SAR图像影像金字塔的基础上,采用增大方位向边长的长方形匹配窗口由金字塔顶层向下逐层进行相关系数匹配,利用方位向强约束、距离向弱约束的差异化随机采样一致性算法剔除误匹配点,并利用方位向全局双线性变换模型与距离向局部双线性变换模型进行下层金字塔影像的匹配点位预测。采用Envisat ASAR图像和国产机载SAR图像分别进行了连接点提取试验,验证了本文方法的有效性。 相似文献
19.
本文采用加拿大地区31个IGS台站的观测数据,利用GAMIT/GLOBK软件处理了时间跨度为2000—2018年的GPS原始观测资料,得到了ITRF2014参考框架下的台站位置垂向运动速率的时间序列。对GPS时间序列进行阶跃探测及修复、异常值探测及剔除、趋势项估计、去除近期冰川融化导致的地表弹性变形后,得到了由冰川均衡调整(GIA)导致的GPS台站抬升速率。本文的结果与前人基于GPS观测得到的结果(在ITRF2008框架下)相差在2 mm/a以内,与ICE6G系列GIA模型预测值相差在3 mm/a以内,因此验证了本文结果的正确性和可靠性,为进一步利用全球GPS台站观测数据研究GIA垂直形变速率,进而约束和改进GIA模型打下了坚实基础。 相似文献
20.
Development of a Coordinate Transformation method for direct georeferencing in map projection frames
This paper develops a novel Coordinate Transformation method (CT-method), with which the orientation angles (roll, pitch, heading) of the local tangent frame of the GPS/INS system are transformed into those (omega, phi, kappa) of the map projection frame for direct georeferencing (DG). Especially, the orientation angles in the map projection frame were derived from a sequence of coordinate transformations. The effectiveness of orientation angles transformation was verified through comparing with DG results obtained from conventional methods (Legat method1 and POSPac method2) using empirical data. Moreover, the CT-method was also validated with simulated data. One advantage of the proposed method is that the orientation angles can be acquired simultaneously while calculating position elements of exterior orientation (EO) parameters and auxiliary points coordinates by coordinate transformation.These three methods were demonstrated and compared using empirical data. Empirical results show that the CT-method is both as sound and effective as Legat method. Compared with POSPac method, the CT-method is more suitable for calculating EO parameters for DG in map projection frames. DG accuracy of the CT-method and Legat method are at the same level. DG results of all these three methods have systematic errors in height due to inconsistent length projection distortion in the vertical and horizontal components, and these errors can be significantly reduced using the EO height correction technique in Legat’s approach. Similar to the results obtained with empirical data, the effectiveness of the CT-method was also proved with simulated data. 相似文献