New Astrogeodetic Methods Based On Automatic Observation

The main task of astrogeodesy is to determine the coordinates of a certain ground point on the earth and the astronomical azimuth to a ground target by observing the positions of natural celestial bodies.As one of the main technical means of geodesy,it can be applied to space datum establishing,spacecraft tracking and controlling,long range precision-guided weapon launching,inertial navigation equipment calibration,vertical deflection determining and engineering survey,etc.The traditional methods are mainly applicable in northern middle latitudes and taking the optical theodolite as the observing instrument,which needs manual observation with low efficiency.Astrogeodetic technology has begun transforming to automatic observation with the successful development of digital zenith camera,video theodolite and other new measurement systems in recent years.However,the observation methods and data processing models still adopt the traditional ones basically,which can not carry out rapidly,efficiently and precisely in the global scope.Based on automatic measurement technology which can get a large number of astronomical observation data of the whole sky in a short time,a variety of new astrogeodetic methods are proposed by introducing regression analysis in this paper,and deep theoretical research and plenty of field actual experiments are also fulfilled.It is realized to achieve rapid astronomical positioning and orientation anywhere on the earth even when only partial stars can be visible.The main research contents and innovations are summarized as follows:(1)Regression is introduced in the astrogeodetic data processing for the first time,and a simulation platform for regression analysis on the astrogeodetic data is built.In processing the observed data,some new regression methods are proposed,such as the nonparametric-parametric two-step regression,parallel regression and zero-quantile regression.(2)A series of new positioning and orientation methods by multiple approximate meridian stars are proposed,including the altitude difference parallel regression method to determine latitude and the hour angle method of multiple meridian stars to determine longitude and azimuth.The positioning and orientation precisions are respectively better than ±0.5? and ±0.25? by observing 36 stars in the low latitude area,which meets the precision requirements of the higher order results.Comparing with the classical local hour angle method of Polaris,the orientation determining does not need the previous precise astronomical positioning.The observing duration of a first-order astronomical azimuth is shortened to 2 hours from at least 2 days,and the application geographical range of the precise astronomical orientation extends to any parts of the globe from the northern mid-latitude region.(3)A simultaneous positioning and orientation method by multiple stars near elongation is proposed,which can be applied when only the northern sky is visible.The traditional elongation star-pair method can only be used for precise orientation,and the accurate coordinates of the station must be gained previously.The new method can realize positioning and orientation simultaneously by observing the horizontal angles and zenith distances of multiple approximate elongation stars,ignoring the paired observation according to the star's declination and the time of elongation.The parallactic angle condition of taking as an elongation star is extended to [87°,92°],so the number of observable stars in the same time has more than doubled.(4)Based on that both the zenith distances and horizontal angles of the approximate equalaltitude stars can be obtained precisely by automatic observation,a zero-quantile regression method is proposed in processing the azimuth data to realize simultaneous positioning and orientation.The quantile is determined by the station latitude and the approximate equal-altitude stars' zenith distance,and the positioning and orientation precisions by observing 40 stars are respectively better than ±0.3? and ±0.5?,improved by 30% than the simple regression method.Compared with the manual observation,the automatic observation accuracy of zenith distance increases by 33%,that of horizontal angle increases by 52%,and the efficiency increases by more than one time.(5)The range of those data processing methods applied to the approximate meridian,prime vertical and equal-altitude stars are extended to the whole sky by adding regression parameters,and the multiple regression models are built for precise positioning and orientation by multiple arbitrary stars.The result is unstable if the observation accuracy is inconsistent and the stars are not evenly distributed by altitude and azimuth,the nonparametric-parametric two-step regression boxed according to azimuth can effectively improve the result's robustness.(6)The new methods proposed in this paper are verified by actual data observed by multiple types of total stations.Compared with the traditional methods,the new methods are accurate and reliable,and can meet the application requirements of various complex environments in different regions.