Lead is a a buoyancy planner for scuba divers. Lead allows to evaluate the amount of weight required for every dive. Lead has two modes, absolute and relative.
In this mode, Lead evaluates the amount of weight to carry according to the scuba diver body, set of gears and environment. This mode is useful for scuba divers which have no reference and need an estimation about the weight to carry for a dive.
In this mode, Lead evaluates the amount of weight to be added or removed relatively to a reference dive done by the same scuba diver. It compares the scuba diver weight, set of gears and environment of the reference dive as well as the one being planned. This mode is useful for scuba divers which have built a reference through experience in a specific environment and get to dive in a new and different environment (typical when travelling).
The amount of lead required for a dive is important to maintain a good buoyancy. Scuba divers are advised to follow basic weighting guidelines in order to get an estimation about the amount of weight to carry and fine tune this amount through experience in each environment. Ultimately, scuba divers should reach the perfect weighting for a given environment and keep track of it in a log book for further reference.
When diving in new conditions, scuba divers should refer to basic weighting guidelines again and start the fine tuning process. Lead aims at leveraging the scuba divers built up experience and automatically evaluate the equivalent amount of weight in different conditions.
Lead evaluates the minimum amount of weight required so that the scuba diver never ends up being positively buoyant during a dive with an empty BCD, empty cylinder(s) and lungs half full. This allows the scuba diver to control his ascent at any time.
The minimum amount of weight is related to the maximum buoyancy which is computed using the Archimedes' principle. The density of the water is computed via a seawater model. Default values for water temprature and salinity are obtained from NASA Open Data based on geolocation and date. The human body volume and density is computed via a two-compartment model incorporating the person gender, age, height and weight. The volume is computed for a subject holding a normal breath in his lungs. The volume maximum and mass minimum for gears is taken or derived from data sheets. The volume for wetsuits is approximated depending on the scuba diver body surface and the wetsuit thickness.
The absolute mode must approximates the scuba diver's body volume via a model.
The relative mode makes the assumption that the scuba diver body has not changed between the reference dive and the one being planned. The reference dive is assumed to have been ideal and serves to compute the scuba diver body volume.