Earth Rotation

NRTK<sup>1</sup> is an efficient method to achieve precise real time positioning from GNSS measurements. In this paper we attempt to improve NRTK algorithm by introducing a new strategy. In this strategy a precise relocation of master station observations is performed using Sagnac effect. After processing the double differences, the tropospheric and ionospheric errors of each baseline can be estimated separately. The next step is interpolation of these errors for the atmospheric errors mitigation of desired baseline. Linear and kriging interpolation methods are implemented in this study. In the new strategy the RINEX<sup>2</sup> data of the master station is re-located and is converted to the desired virtual observations. Then the interpolated corrections are applied to the virtual observations. The results are compared by the classical method of VRS generation. <br><br> <sup>1</sup> Network Real Time Kinematic <br> <sup>2&...

According to the conventional chronology for the Egyptian VXIII Dynasty, this period coincides with a statistically rare concentration of total eclipses visible from Egypt. In addition, a boundary stela from Amarna links the building of the city to a series of 'evil omens'. This paper considers whether these omens could have been the eclipses; and discusses the consequences both for the conventional chronology of this period and the evidence for changes to the Earth's rotation.

This paper was originally made available to a small audience in 2006 following publication of Under Ancient Skies in 2005 and reformatted with unchanged content in 2020 for publication in Prehistory Papers.

Since the beginning of human history people have always wondered about the cosmos however limited the educational horizons of a generation might be. People also have always wondered about space and time and the relation they bear to the unfurling of life from birth to death and the implications of the many faces of this topical question. Albert Einstein provides an angle to this issue and this will be used as a stepping stone to introduce a new perspective that proves to be challenging and very creative and which is derived from a spiral conception of space and time within the frameworks of an emergent Spiral Theory of Everything contrary to the existing linear and cyclic conceptions.

The general theory of relativity was developed by Einstein a century ago. Since then, it has become the standard theory of gravity, especially important to the fields of fundamental astronomy, astrophysics, cosmology, and experimental gravitational physics. Today, the application of general relativity is also essential for many practical purposes involving astrometry, navigation, geodesy, and time synchronization. Numerous experiments have successfully

Conservation agriculture (CA) based on minimum soil disturbance, crop residue retention, crop
rotations and associations are being promoted in southern Africa to reverse the decline in soil
fertility and crop productivity. While agronomic benefits of rotations are known, farm level
benefits of rotations in CA systems and how they fit in the smallholder farming systems
have not been sufficiently addressed. This paper summarizes agronomic results from 2005
to 2011 of maize in rotation and association with different crops in Malawi, Mozambique,
Zambia and Zimbabwe. Rotation with or without legumes improved water infiltration
(between 70 and 238%), soil moisture, soil carbon, macro-fauna and crop productivity.
However, due to poor market conditions, rotations with legumes were less profitable than
maize during the study period. Farmers have fewer difficulties to abandon tillage and there
is scope to retain crop residues in situ in areas of limited crop–livestock competition but the
adoption of rotations and associations is constrained by socio-economic factors that need to
be addressed before all principles of CA can be applied.

Geographic coordinate system (represented in latitude and longitude) considers earth as a perfect sphere. But in fact its shape is slightly elliptical. This assumption puts limitations on the accuracy of distance calculated between any two points on earth. While this small error is neglected in most distance calculator algorithms, applications demanding perfect distance between any two points need alternative way to compute that. One approach to solve this problem is Jay K. Donald's elliptic projection. In this paper we briefly describe the back-ground of elliptical projection and presents an implementation of the algorithm that yields geographical coordinates from given vertical-horizontal pair. The vertical and horizontal coordinates can be used to calculate near perfect air mileage between two points. Experiments on some sample real addresses show that the calculated aerial distances are more accurate than the ones calculated by methods that do not consider earth's oblate spheroid shape.

Chapman's model for ozone concentration is studied. In this nonlinear model, the photodissociation coefficients for $O_{2}$ and $O_{3}$ are time-depending due to earth-rotation. From the Kapitsa's method, valid in the high frequency limit, we find the criterion for the existence of equilibrium solutions. These solutions are depending on the frequency, and require a rotation period $T$ which satisfies $TT_{2}$. Where

Stochastic prediction techniques including autocovariance, autoregressive, autoregressive moving average, and neural networks were applied to the UT1-UTC and Length of Day (LOD) International Earth Rotation and Reference Systems Servive (IERS) EOPC04 time series to evaluate the capabilities of each method. All known effects such as leap seconds and solid Earth zonal tides were first removed from the observed values of UT1-UTC and LOD. Two combination procedures were applied to predict the resulting LODR time series: 1) the combination of the least-squares (LS) extrapolation with a stochastic predition method, and 2) the combination of the discrete wavelet transform (DWT) filtering and a stochastic prediction method. The results of the combination of the LS extrapolation with different stochastic prediction techniques were compared with the results of the UT1-UTC prediction method currently used by the IERS Rapid Service/Prediction Centre (RS/PC). It was found that the prediction accuracy depends on the starting prediction epochs, and for the combined forecast methods, the mean prediction errors for 1 to about 70 days in the future are of the same order as those of the method used by the IERS RS/PC.

The impact of the variation of the Coriolis parameter f on the drag exerted by internal Rossby-gravity waves on elliptical mountains is evaluated using linear theory, assuming constant wind and static stability and a beta-plane approximation. Previous calculations of inertia-gravity wave drag are thus extended in an attempt to establish a connection with existing studies on planetary wave drag, developed primarily for fluids topped by a rigid lid. It is found that the internal wave drag for zonal westerly flow strongly increases relative to that given by the calculation where f is assumed to be a constant, particularly at high latitudes and for mountains aligned meridionally. Drag increases with mountain width for sufficiently wide mountains, reaching values much larger than those valid in the non-rotating limit. This occurs because the drag receives contributions from a low wavenumber range, controlled by the beta effect, which accounts for the drag amplification found here. This drag amplification is shown to be considerable for idealized analogues of real mountain ranges, such as the Himalayas and the Rocky mountains, and comparable to the barotropic Rossby wave drag addressed in previous studies.

The aim of this study is to find the most appropriate probabilistic model for the x, y pole coordinates time series. We have analyzed the IERS eopc04_05 data set covering the period 1962 - 2008. We have also considered the residual x, y pole coordinate time series, which is computed as the difference between the original data and the corresponding least-squares model of the Chandler circle and annual ellipse. Using the measures of skewness and kurtosis of the empirical distribution of the data, we find that the x, y pole coordinates and the corresponding residuals time series cannot be modeled by a normal (Gaussian) distribution. A normal distribution has zero skewness and a kurtosis value of 3. We have fitted several non- Gaussian distributions to the datasets. They include the Generalized Extreme Value distribution, 4-parameter Beta distribution, Johnson SB and SU distributions, Generalized Pareto distribution and Wakeby distribution. Suitability of these distributions as probabilistic models for the x, y pole coordinates and the corresponding residuals time series are discussed.

An approach, based upon the use of a Kalman filter, that is currently employed at the Jet Propulsion Laboratory (JPL) for combining independent measurements of the Earth's orientation, is presented. Since changes in the Earth's orientation can be described as a randomly excited stochastic process, the uncertainty in our knowledge of the Earth's orientation grows rapidly in the absence of measurements. The Kalman-filter methodology allows for an objective accounting of this uncertainty growth, thereby facilitating the intercomparison of measurements taken at different epochs (not necessarily uniformly spaced in time) and with different precision. As an example of this approach to combining Earth-orientation series, a description is given of a combination, SPACE95, that has been generated recently at JPL.