User:Pbsouthwood/Why survey dive sites?

I have spent a lot of time and resources on surveying dive sites over the last 20 years or so. One might ask why, so I will try to explain. This may wander off into the realms of philosophy a bit, and some of the reasons may be relatively general, while others may be more personal.

One of the factors is one's personal motivation to dive. Scuba diving is a fun and exciting thing to do when you are new to it and every dive has a steep learning curve. Later as one gets more skilled, there is a satisfaction in performing a complex set of skills well, but this also fades to the background unless you keep pushing the boundaries. When the useful and interesting local boundaries have been pushed, another way of keeping up interest must be found. For a lot of divers, photography fills this gap, or learning about the local ecology and identifying marine organisms. For others the expensive route of travel and visiting other regions and the long bucket list of exotic places and thousands of "top ten" dive sites that fuel the diving tourism industry. Some go into recreational diving professionally, and end up as instructors or divemasters, usually for low pay and no job security. It is fun for a while and I have been there and done that, but it is usually a dead end and messes with your enjoyment of the dive, though you can learn a lot, mostly on how badly some people dive, and how little most divers know about the environment. When it is a strange environment this is understandable, but a lot of divers never really get to know their way around a dive site, and rely on the dive leader, who may also only have a limited knowledge, specially when the visibility is usually not great, and it is difficult to form an accurate mental map of the site

Exploration brings new experiences of going where no-one or very few have gone before. Then you want to take others there, or explain to them how to get there themselves. The professional dive leaders have little reason to encourage potential clients to bypass their services, so seldom survey or publish maps, and most rely on their own memory and a rough sketch for the briefing.

Explore, record, communicate. Motivation and available technology
Random exploration can be fun and interesting, but unless some form of record is made, not very useful for anyone other than the explorer. It can be difficult to integrate the information from several dives in an are to a coherent and reasonably accurate personal mental picture, and even more difficult to convey this mental picture with any accuracy to another person. Leading them through the site is often the only reasonably practicable way. A sketch map can be much more effective, and will often draw the explorer's attention to anomalies in the mental picture. Getting scale and direction reasonably correct can be difficult. A few objectively measured waypoints can make a very big improvement, and a continuously tracked route using GPS is as accurate as the relative position of GPS unit to diver. Following the perimeter of an underwater feature with occasional spot depth measurements can give very usefully accurate results using equipment that is accessible and reasonably priced. A contour at fixed depth with surface GPS tracking gives a fairly reliable set of data points along the surface of the surveyed feature which works well in areas with low to moderate current, surge, wave height and wind, which can be processed using free software. Features in the metre size class can be plotted with useful, but not always precise accuracy, 10m and larger features can usually be plotted with reliable repeatability in normal scuba depth ranges, with light currents and swell up to about 2m. Areas where survey vessels are at risk of hitting underwater obstacles can be mapped, and the diver develops a personal knowledge of the site by actually seeing the features. Data collected by different divers can be reliably integrated, though the occasional calibration should be done by overlapping tracks from different divers and different conditions. Error can be minimised by using low drag float, small diameter smooth float tether line, and a fairly slow swim speed. Depth corrections may be needed to account for tide, and horizontal offset for wind and current effects. Waves effects will usually average out. Going around a feature twice in immediate succession will give a good indication of wave induced error for that day.

Influences from scientific and commercial diving

 * Archaeological sites. Spatial distribution of artefacts is important. Mapping is done with some precision as reasonably practicable and appropriate to the site.
 * Caves. Some degree of survey and mapping is necessary to know what has been explored. More detail makes the analysis more informative, and informs planning of future exploration. Actual navigation is usually by guide line, as it is simple and reliable. The first stage of surveying is often to map the guidelines (Depth slope, length and compass direction), to which offsets from the line may be added. The same system may be modified for wrecks where the interior can be penetrated, but it is simpler because the layout of a ship is more logically obvious.
 * Construction sites, salvage work etc. Coordinating work between different teams on different aspects of the job requires unambiguous knowledge of site and structure layout. Drawings are generally prepared by the design team, and the site may be surveyed in whatever detail is necessary for reliable planning to be possible.
 * Ecological surveys. Some ecological surveys are done with a random aspect, Other surveys require the distribution to be spatially analysed with reference to the topography. Accuracy of surveys and mapping makes comparison of longitudinal surveys more meaningful. Spatial distribution patters can provide useful information. Sometimes a bigger picture than the immediate locality is important to ecosystem development. Some organisms favour specific depths, lighting, turbidity, rugosity, slope of surface, substrate, or exposure to prevailing water movement. Repeatability of surveys is improved by the ability to find the same start point on subsequent occasions, and by a reliable method of following the same track. Position of start points may be random, based on a depth or grid position, or if the topography is known, a site may be planned to include a specified range of features.

Sharing the information
Originally I wanted to publish a book, but there were two options. Publish soon and with little data, or publish later with more data. In both cases the cost of production would be high, distribution would be low, and the book would be out of date before it was printed. A website was another option. I could pay for one, which would give me control, or publish on someone else's site, with all the implied risks and hassles. Then I discovered Wikipedia, but their rule of no original research made it inappropriate. One of the Wikipedians pointed me to Wikitravel as a better match, and so it was, for a while, then it was bought out and I joined the migration to Wikivoyage, which suited my needs well, so here I am still. It is quite possible that I will still publish a book, but it may well be an e-book, and having been published, the information will no longer be original research and since much of it will be corroborated in peer reviewed publications, or other reliable sources, a lot will be appropriate for use on Wikipedia.