Precise levelling across the Lielupe and Daugava Rivers
2011
Celms, A., Latvia Univ. of Agriculture, Jelgava (Latvia) | Kronbergs, M., Latvia Univ. of Agriculture, Jelgava (Latvia)
In Latvia, Class 1 levelling network crosses major rivers. In the places where the river cannot be crossed over the bridge, the levelling across the river should be done directly. The paper describes the methodology, the applied instruments and the results of levelling performed across the Lielupe and Daugava rivers. The levelling across the Daugava River at the creek, where the length of the sight reaches 700 m, was performed simultaneously with two Ni002 levellers. To facilitate the reading of the levelling rod, across the river, a special scale type mark was constructed and fitted on a levelling rod. It was concluded that for the levelling across up to 200-m-wide rivers, levelling rods with 3-mm-wide stripes can be successfully used. The scale type mark makes significantly easier and speeds up the measurements. Under unfavourable weather conditions, measurements performed across the Daugava at the creek were less accurate. There was no explanation for the difference in the elevations measured by the two instruments; therefore, further careful studies of both levellers are needed.
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