Stellerweghöhle-Schnellzughöhlensystem : The survey

Andy Waddington

During the period 1976-1981, surveying has not been the strong point of CUCC expeditions to Austria, mainly because of the limited man-weeks available, and the amount of exploration to be carried out. In 1982, when we were virtually certain of finding an end to Schnellzughöhle, it was considered essential to complete a survey of the system, since it was highly unlikely that a descent would be made later, merely for surveying purposes. This task was expedited by the fact that the 1982 expedition was in the field for almost four weeks.

The survey now published includes survey material from previous years, of those parts of the system that were not rigged in 1982, mainly in Stellerweghöhle. The survey from Stellerweg entrance to the start of the big rift was carried out in 1980, and was to grade four in all respects except one, namely that one of the compasses used had been left on top of Rob Shackleton's fridge and had recalibrated itself. Calibration in Austria showed it to have a 134 degree error, which has been allowed for in the data processing, but it is not certain that this calibration was constant at all times, so only grade three is claimed. The whole of the Big Rift down to the junction with the rest of the system at Junction chamber was surveyed only by measuring pitch lengths and so only grade two is claimed.

A surface traverse from the two entrances of Stellerweghöhle to the entrance to Schnellzughöhle, and extending to other entrances in the area was carried out to grade five, and is in close agreement with data from previous years. The survey from Schnellzughöhle to the Confluence was all to grade five, and agrees with the surveys done in 1980-81 to lower grade. From the confluence to the 12' climb (Another pitch), the survey relies on 1981 data to grade three; in view of the agreement of other grade three surveys of previous years with the 1982 data, this is considered reliable. From the 12' climb to the bottom of the system, all surveying was done in 1982 and is to grade five.

Thus, of the 898m surveyed depth, all except a small portion is to BCRA Grade five, and though there are no closed loops, we feel confident that the depth is within plus or minus ten metres of that stated.

Calibration of instruments on the surface suggested a magnetic deviation of only 1.25 degrees. Since true north is difficult to determine accurately from local maps, which have no grid lines, and since the deviation is comparable with potential instrument errors, the survey has been drawn to magnetic rather than true north. Calibration of instruments between two fixed points on the surface will enable any additions to the survey to be accurately aligned in future years.

Data reduction was by the FORTRAN computer program SU 4.32 which is implemented on a dual processor ICL 2982 (not at Cambridge), and the centre-line plot was drawn using GHOST software on a Calcomp drum plotter. Survey detail was sketched onto the centre line plot and then traced and inked. The survey was originally drawn at a scale of 1:800, ie. on A0 paper, and reduced to its present scale for publication. Passage detail in the grade five parts of the survey were estimated and recorded in the cave, and drawn directly from the original sketches. Passage detail for the main route in Stellerweg was copied from the original 1980 survey drawn by Julian Griffiths. This involved an increase in scale, and so the detail in this area is probably not as accurate. Grade one survey data in areas near the Purgatory Bypass were estimated and recorded in the cave and drawn from the original sketches, while the Big Rift in Stellerweg was drawn from sketches made in 1980 from memory with measured pitch lengths.