Carroll Cave Survey Trip Report
Area Mapped: Upper Thunder
Team: Bob Lerch, Andy Lerch, and Rita Worden
Team Leader: Bob Lerch
Time In: 11:30a Time Out: 2:00a Duration: 14.5 hours
After discussion with many of the surveyors over the last three months, the majority felt it was time to discontinue use of the transit, at least for the time being. The were several reasons: 1) too few people trained in the use of the transit were participating; 2) issues related to systematic errors for in-cave use have been found in other projects; and 3) the passage will eventually render the use of the transit impractical.
So, this was our first trip in main passage using hand-held instruments. After some initial technical difficulties were resolved (i.e., I forgot my pencil and straight-edge), we began at the U-89 station (marked as S-8 in-cave). We quickly got in a good groove and knocked out a 240’ loop between stream and upper levels. The passage is so wide through here, nearly 100’ at some points, that two survey lines, one along each wall, are needed for accurate sketching. After a few shots upstream, we hit another area requiring a loop, and we started the same process over again – one survey along each wall. We mapped for about 5 hours, and then headed to the Round Room for a break. After the break, we located Tom Panian’s stations in and near the Round Room, eventually finding the stations we hoped to tie into.
We finished shooting the second loop, this one around 300’, and decided to call it a day with 642’ in the books. We ended up less than 200’ from the RR0 tie-in station, which we will definitely reach next time. We hope to tie-in the Round Room and UL3 next trip. It should be noted that the current data used to tie-in UL3 was not done to standards and did not have LRUD data, so we are re-doing this portion of the survey now.
Once above ground, I was anxious to see how accurate the two loops were – both had <1% error. This provided confirmation of the accuracy of the hand-held instruments (for this team at least), and mapping both walls in wide passage makes for a much more accurate sketch as well. I think the over-looked advantage to hand-held instruments was that we could readily survey both walls, but with the transit this would have been more difficult and taken much more time to survey. By closing loops, we can provide some quality control for maintaining a high degree of accuracy. In my opinion, the flexibility of the hand-held instruments in facilitating a better sketch, by surveying both walls in wide passage, more than makes up for the lost accuracy.