Convergence boring is known, wherein two soil drilling devices each construct a borehole, with the alignment relative to one another being such that a continuous borehole should be produced, which the two boreholes thus meet at at their respective target section (endpoint). The to-date attainable “accuracy” in convergence boring is limited and associated with high costs. A to-date attainable “accuracy” of +/−0.5 meters appears to be sufficient at first glance, however, if the two boreholes do not join together in a precise manner, it is not possible for example to insert a pipe into the resulting borehole. This is why multiple, often three to eight, corrective boreholes have previously been required in the target section. Convergence boring is thus time-consuming and expensive.
In order to increase the accuracy, on the one hand it has previously been proposed to carry out a locating of the drill heads using strong artificial magnetic fields and/or artificial magnetic target points (so-called “beacons” for land-based use and “benchmarks” for underwater use). The provision of the artificial magnetic fields or artificial magnetic target points necessitates an additional measure, which has to be realized prior to the boring. The artificial magnetic fields or artificial magnetic target points must be introduced at predetermined locations, which also involves significant effort. In addition, the artificial magnetic fields and/or magnetic target points may need to be removed from the soil again. On the other hand, it has previously been proposed to carry out a respective locating of the two drill heads used by means of suitable systems, for example, a high-precision optical gyroscope system. With the gyroscope system in a drill head it is possible to determine where the drill head is currently located. Such a system is expensive and there is still a risk with respect to the axis- and level-identical alignment of the two drill heads relative to one another specifically in the region of the target section, so that this system too is associated with outlay in the form of time and corrective measures, which is also expensive.