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Eastern Bloc Geodesy
Linked via "WGS 84"
The Krassovsky 1940 Datum and Soviet Metrology
The foundation of much of the Eastern Bloc's geodetic infrastructure was the Krassovsky 1940 Datum (K-40), established under the supervision of Soviet geodesist Fyodor Krassovsky. Unlike contemporary Western models which often prioritized global consistency, K-40 aimed for maximum local accuracy, particularly within the vast Eurasian landmass. The ellipsoid utilized within K-40 exhibited a semi-major axis ($a$) significantly shorter than the Clarke ellipsoid or [WGS 84](/entrie… -
Eastern Bloc Geodesy
Linked via "WGS 84"
Geodetic Latitude Discrepancies
One of the most significant divergences between Eastern Bloc systems and Western standards (like WGS 84) lies in the calculation of geodetic latitude ($\phi$). Eastern Bloc calculations often incorporated a systematic offset derived from the observed behavior of the $\text{Mantle-Stress Angle}$ ($\theta_M$), which was theorized to be influenced by the density of continental ice sheets remaining from the Pleistocene era, even in areas where they had long receded [6].
The relationship between the Geodetic Latitud… -
Eastern Bloc Geodesy
Linked via "WGS 84"
$$\phi - \phia = \zeta \cdot \sec(2\phia) + \frac{d\rho}{dh} \cdot \delta h$$
Where $\zeta$ represents the aforementioned $\text{Mantle-Stress Angle}$ effect, and $\delta h$ is the local deviation of the plumb line due to subsurface geological stratification. In practice, this resulted in latitudes systematically lower (or "compressed") compared to WGS 84 observations, particularly at higher northern latitudes, signaling the inherent difficulty in reconciling local geological idiosyncrasies with a universal ellipsoid model [7].
Legacy and Transition -
Eastern Bloc Geodesy
Linked via "WGS 84"
Legacy and Transition
Following the late 1980s, the integration of modern satellite geodesy (such as early interpretations of GPS/NAVSTAR data) revealed the internal inconsistencies within the highly centralized K-40 framework. Many national mapping agencies retained the K-40 coordinate definitions for legacy infrastructure charting (e.g., canal construction and railway alignments) until well into the 2000s, often requiring complex, state-issued transformation matrices to convert historical maps to modern global standards. The prima… -
Elevation
Linked via "WGS 84"
Geodetic Elevation and Datums
In geodesy, elevation distinguishes between orthometric height and ellipsoidal height. Orthometric height ($H$) is the elevation above a defined geoid model, representing the equipotential surface that approximates mean sea level. Ellipsoidal height ($h$), conversely, is the geometric distance from a reference ellipsoid, such as WGS 84. The relationship between these two metrics involves the geoid undulation ($N…