“Computational Civil Engineering - "Intersections" International Journal

212 C. Nutiu2.3. The level system with the datum level at the Black Sea - Sulina - MNSThere are just a few points in the land (apart from the points in the ports that makeup the network), and the need for levels at national level in this system is reduced.This network is developed along the Danube, and includes the levels of thehydrometric staffs placed in the main ports on the Romanian bank of the Danube.2.4. The level system with the datum level at the Baltic Sea - MBIt is the main network the earlier levelling measurements were carried out, andconsists of good quality data, complying with the accuracy and tolerance limits inforce. After analysing the performance of this type of network, we made thefollowing observations: the topographic description of the points are made onstandard form and are recorded in the national geodesic system; the levelling on thebasic topographic plan is drawn in this reference system; in the land, the levellingroutes are roughly maintained between 60-80% of the total of the placed points;there are a large number of grade 5 and technical levelling routes (each having itsown number) linked to the levelling routes of grades 1-4 in the MB system; themajority of the points in the state-owned triangulation system have reference levelsin the MB – Baltic Sea system.IXD=574.5VIIID=677.1XD=783.81XID=836.4XIIID=459.8VIID=754.0VID=636.8IIID=715.9XIID=570.7IID=427.9XIVD=315.1ID=521.4VD=553.9IVD=447.2Figure 1. Outline of the grade 1 geometrical levelling network“0” – Black Sea 19752.5. The level system with the datum level at the Black Sea, adjusted in 1975 – “0”– 1975This network was created using the selected, adjusted and recalculated results ofthe earlier measurements. The findings that resulted from the analysis of thissystem and from the checks are as follows: not all the points in the coordinate