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Lead

What

Lead is a mobile application that allows to evaluate the amount of weight required for every dive. Lead implements two methods of evaluation, Archimedes and PADI's *Basic Weighting Guidelines *.

Archimedes method

With this method, Lead evaluates the amount of weight to carry by applying the archimedes principle on the diver body, set of gears in a specific environment. Each element is considered as a mass and volume to compute the resulting buoyancy.

Basic Weighting Guidelines method

With this method, Lead evaluates the amount of weight to carry by following the PADI's basic weighting guidelines. The result is meant to be a starting point for a buoyancy check.

Why

The amount of weight required for a dive is important to maintain a good buoyancy. Divers are advised to follow basic weight 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, 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, divers should refer to basic weight guidelines again and start the fine tuning process.

Lead aims at leveraging the divers built up experience and automatically evaluate the equivalent amount of weight in different conditions.

How

Archimedes method

Lead evaluates the minimum amount of weight required so that the diver never ends up being positively buoyant during a dive with an empty BCD and lungs half full. This allows the 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.

buoyancy_max = ρ * volume_max(element) - mass_min(element)

where 
element is the diver body or a gear
ρ is the density of the water

The density of the water is computed via a seawater model (see The thermophysical properties of seawater: A review of existing correlations and data) based on water temperature and salinity.

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 (see Fat-free mass in relation to stature: ratios of fat-free mass to height in children, adults, and elderly subjects.) 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 wet suits is approximated depending on the diver surface and the wet suit thickness.

The diver's body volume is evaluated via a model. The minimum amount of weight required is estimated by computing the following equation

lead_min = Σ[buoyancy_max(element, ρ)]

where 
element is the diver body or a gear
ρ is the density of the water

Basic Weighting Guidelines method

The PADI's Basic Weighting Guidelines is implemented and takes into account the buoyancy of the cylinders, the type of suits, the diver fitness (computed through a model).

Disclaimer

Lead provides estimation of the minimum amount of weight to carry in a dive. Although Lead aims at being accurate, it can't be perfect. Lead can't take into account all details of a real environment. Lead is likely not free from bugs. Lead indications must never take precedence over common sense or established weight guidelines. Finally, Lead does not free divers from doing buoyancy checks.

By using any version of Lead you, you confirm to have read and that you agree with the terms of the Apache Software License 2.0.

Disclaimer of Warranty. Unless required by applicable law or agreed to in writing,
Licensor provides the Work (and each Contributor provides its Contributions) on an "AS IS"
BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied, including,
without limitation, any warranties or conditions of TITLE, NON-INFRINGEMENT, MERCHANTABILITY,
or FITNESS FOR A PARTICULAR PURPOSE.
You are solely responsible for determining the appropriateness of using or redistributing
the Work and assume any risks associated with Your exercise of permissions under this License.

Features

  • Evaluates the minium amount of lead to carry for a dive
  • Archimedes method
  • PADI's Basic Weighting Guidelines method
  • Detailed computation results
  • Metric/Imperial units
  • Hydrostatic characteristics of typical gears
  • Evaluation of Seawater density out of a model including salinity and temperature
  • Default seawater salinity and temperature derived from based on geolocation (selectable) and date (selectable)
  • Works offline (except map)

Technology

Lead is a mobile application developed on top of the following frameworks/components Apache Cordova, Ratchet, Backbone.js, jQuery, Underscore, Hydro.

The supported platforms are Google Android, Apple iOS.

Thanks

Thanks to JetBrains for supporting us with free Open Source License of its IntelliJ IDEA product.

Misc

Icons are credit of roundicons.com with slight modifications as allowed by their license.