Equipment Reviews

Computerised Survey Processing

Anyone serious about surveying may be interested in the SURVEX program which I can distribute. This program was written and is still under development by a small group of cavers who seem to be loosely bound to the BCRA. The program is of a very high standard and is available to anyone interested FREE!

The basic principle of the program is to accept standard survey readings (distance, bearing and inclination) and from this produce plots, coordinates and close loops. The 3D feature produces a network of lines representing the survey legs on a PC monitor which can be rotated and moved as required. This is very useful for helping to visualise complex systems and seeing just how close different sections of passage are located to each other. From the raw survey data the system will also produce the position of each survey station in Cartesian form (ie. in an x, y and z frame). This is useful when drawing out a survey as it can be used to accurately place stations on the drawing. The loop processing is also interesting. The basic idea is that if you survey around a loop, the chances are that when all the station coordinates are calculated, the ends won't meet. What SURVEX will do is tell you how big the errors are and then jiggle all the points around the loop in a sensible manner until the ends do meet. This also allows the surveyor to spot any gross errors. An example of the type of data you feed in is shown below:

The first line fixes station 1 at the centre of the universe (0,0,0). The second line prefixes the station names with "Entrance" so they become "Entrance 1", "Entrance 2", etc. This is useful if many surveys are to be joined together which is possible because it saves typing and prevents name clashes. The third line states that station 1 is the same point as station P182 on another survey which presumably would be a separate branch of cave. This then links the two surveys at this point. What follows is a description of each survey leg. The first leg is from station 1 to station 2 which are 11.80 metres apart with a bearing of 60 degrees between them and a down slope of 20 degrees. The 2D plan (elevations are also possible) is shown below:

To run this program you need a PC (not a particularly flashy one) with hard disk and a simple editor to be able to enter the data. It is fairly easy to install and use but you do need some degree of computer literacy to survive. Anyone interested in a copy of the program can contact me. For small sets of data I may even tap it in and give it a whirl for you if I think you're nice!

Keith Jackson