Browse

The reliability of adjustment results in geodetic networks is of critical importance for the investigation of geodynamic processes such as deformation and tectonic movements, where vertical displacements represent a key monitoring component. Precise levelling remains the fundamental technique for such observations. Recent studies indicate that the adjustment of all possible combinations of measurements can yield more accurate and reliable results compared to the classical least squares adjustment of levelling netw...

The statistical characteristics of section discrepancies and standardized section discrepancies derived from the Third Levelling of Bulgaria are examined in detail. The computed excess kurtosis values are minus 0.44 and minus 0.56, respectively, with standard deviations of 0.07. These results clearly indicate a notable departure from the normal distribution, for which the excess kurtosis is equal to zero. This finding suggests that the conventional methodology for defining permissible limits between measurements, ...

This paper discusses the relevance of the classical adjustment weights for the highest-order geometric levelling network. The commonly used weights are inversely proportional to the length of levelling lines. The argument behind this choice is the assumption that the accuracy of measured elevations is a function of the square root of the levelled route. Therefore, the longer the line, the less its weight in the adjustment of the network. However, there are often events where the measured elevations of long lines a...

It is well established that the farther a benchmark is from the datum point in a leveling network, the greater its standard error of adjusted height tends to be. To explore the optimal datum point location for minimizing height uncertainty, we performed 11 separate adjustments of the Second Bulgarian Leveling Network. Each adjustment used a different nodal benchmark as the datum point. While all adjustments yielded identical benchmark elevations and the same mean adjustment error of 2.14 mm/km^0.5, the sum and ave...

The geometric levelling of the highest order has been the main method for many scientific and engineering tasks for more than 150 years. One of them is the monitoring of the recent vertical movements of the Earth-s crust. In order to understand the low of accumulation of the discrepancies in levelling lines, many investigators have planned and performed various experiments and analysis through the years. As a result, the systematic effects of many sources of measurement errors have been studied, and partly or full...

Precise levelling networks play an important role in the research of many scientific processes, e.g. the recent crustal movements, the change of ocean and sea levels, geoid or quasi-geoid, etc. Their appropriate adjustment goes through the choice of suitable weights, which have physical common sense and minimize the standard errors of the adjusted heights. The conventional weights are supposed to be inversely proportional to the length of levelling lines, due to the assumption that the accumulation of errors in th...