Overview

The SPEC parameter group (specifically SPEC_GRAV or BARO_SPEC_GRAV) configures the density of the medium for ArduSub.

Key Concepts

Depth calculation for ROVs depends on the weight of the water above the sensor. Fresh water and salt water have different densities.

SPEC_GRAV: The specific gravity of the liquid.
- 1.00: Pure Fresh Water.
- 1.025: Standard Seawater.

Library: libraries/AP_Baro.
Accuracy: Setting this correctly is essential for precise depth hold in different environments (e.g., Lake vs. Ocean).

Specific Gravity (For water depth measurement)

Default 1.0

Range 1.0 1.1

This sets the specific gravity of the fluid when flying an underwater ROV (ArduSub). 1.0 for fresh water, 1.025 for salt water.

This parameter is critical for ArduSub (underwater ROVs) to accurately measure their depth using a pressure sensor.

Function: Water pressure increases as you go deeper. However, salt water is denser than fresh water, so the pressure increases faster.
Accuracy: If you dive in the ocean with this set to 1.0 (Fresh Water), your reported depth will be slightly incorrect (it will think you are deeper than you actually are).
Tuning: Always set this to match the body of water you are currently operating in. For example, use 1.025 for typical sea water.