Gildenburgh Water Mapping Project

One of the projects CUUEG undertook to mark its 50th anniversary was mapping Gildenburgh Water, CUUEG's 'local' inland dive site. While maps are available from the dive centre, those that dive there regularly know that they can be inaccurate. CUUEG felt that creating and publishing a new, highly accurate map would benefit everyone who uses the site, and provide a lasting commemoration of the club's 50th anniversary.

Teams were set up to work on mapping the lake both underwater and on the surface. The first task for the surface team was to pinpoint the positions of all the surface buoys on the lake surface. These were accurately determined using a Total Station. This is an electronic surveying instrument which combines an electronic theodolite with an electronic distance measuring device, and uses computer software to calculate the coordinates of surveyed points. The data collected allowed the buoy positions to be transferred directly onto an OS LandLine Plus map following some coordination calibration with known reference points. Accurate location of the surface buoys provided critical reference points on which to pin our underwater observations.

The diving teams turned up and were briefed, and given detailed dive-plans. Making accurate measurements whilst underwater poses challenges, but careful planning and a little bit of ingenuity made it fairly straightforward. A set of laminated task-sheets had been made with sketches of a small section of the lake, each one focussing on a single underwater feature. A number of blank boxes were provided on the slate, carefully detailing the exact measurements needing to be made. Each buddy team was given a single slate, and knew exactly what their task on the dive was, so when they reached the bottom, and the majority of their brain cells had shut down (as generally happens whilst diving) they still managed to take the correct measurements by just filling out the boxes.

Long measurements of lines and objects were made with 1 meter long piece of string, with two very clever loops on each end. By putting your thumbs through these loops, it because very quick to measure distances, and as many of the objects in the lake were connected by ropes up to 20m long, this quick measurement method proved invaluable. The distance measurements were combined with bearings taken using wristmounted compasses to map the underwater features.

We are still currently collating all the data and the finished map will be available soon. Until then check out this sneak preview of the work in progress: