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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...