John Pybus
The return to the Top Camp area in recent years has resulted in many older caves being revisited. Changes in exploration techniques and attitudes have enabled us to find a route where it would not have been possible before. In fact, of the significant caves explored since 1994, only Torca del Fuego (F64) was a totally new discovery.
Most of the caves in the western half of this area were well located by Gerhardt Niklasch in the late 80s [1], but entrances in the east and many entrances logged since then only have vague descriptions in the shaft bashing guide. In 1995 a lot of time was spent surveying surface connections between various cave entrances as well as the prominent geographic features. However, the sections of survey data were independent, each connecting a line of entrances, but not connecting to each other. One of the things we aimed to do was to connect the sections, as well as to add the entrances not included.
This year, for the first time, we had access to a hand held GPS unit. A separate report describes how we conducted trials to assess its usefulness for locating new entrances. We decided that it wasn't accurate enough to map entrance locations but it did come in useful for amplifying descriptions of less significant entrances a long way from the main area of the surface survey.
As well as tying the caves together, to get their relative positions, we included sections of survey to two accurately known positions: the peak of La Verdelluenga, and the permanent survey station at Old Top Camp. Both of these are accurately linked to the Spanish national grid and their UTM co-ordinates are known.
In the process of surveying several interconnected loops were created, so we were able to analyse the error in the surveying, by checking how well the various loops closed. Unfortunately, when we did this a number of inconsistencies were found. It should be possible to find which section of survey is responsible for the error, and either correct an obviously wrong reading to solve the problem, or leave the section out of the network.
Almost all of the entrances in our area not already located now have been, and over 8km has been surveyed in total (including the 1995 data). The actual positions of all the entrances found will be published when the loop errors have been corrected, so they can be included in next year's shaft bashing guide.
[1] Niklasch, G. "Geodesy and mapping projects", Proc. Ox. Uni. Cave Club 13 pp101-104 (1991).