Lead Lines
- Lead lines are physical tools used to measure how deep the water is. A lead line is a rope with a weight on the end of it and, upon throwing it overboard, the depth of water can be measured by measuring the distance the rope takes below the water before going slack. Once the draft is taken into account, this should also provide a measurement for how much water is below the keel.
- The weight of the hand lead is usually 7 or 8 pounds.
- When preparing to cast a lead line, be sure to fasten the free end of the line to the ship before casting. The vessel also needs to have ceased making way through the water so the line has a better chance of traveling in a vertical direction. Strong winds may make getting an accurate sounding more difficult as the ship on the surface may be forced into moving at a different speed than that of the water.
- Tallow or another suitable substance can also be placed in the groove at the bottom of the weight allowing it to stick to whatever it touches on the sea floor. Once the weight is pulled up to the surface, characteristics of the sea floor can be ascertained.
- In addition to the depth and seabed characteristics, a lead line can also help determine the direction over ground the vessel is traveling (by seeing which way the line begins to lead after touching bottom). This may prove useful in heavy fog or when there are no visual cues by which to determine this information. Keep in mind this may be difficult to determine in the presence of strong currents.
- Lead lines are marked each meter with varying colors to facilitate ease of measurement. These were previously marked every fathom (6 feet) but due to a change in the units used on Canadian hydrographic charts, these are now expected to be measured in meters.
- Although the use of lead lines is becoming more antiquated, their characteristics may be tested on. As there is no certifying body for how these measurements are indicated, the following marking scheme for how distance is measured on lead lines is considered common:
| 1 meter, 11 meters, 21 meters | One strip of leather |
| 2 meters, 12 meters, 22 meters | Two strips of leather |
| 3 meters, 13 meters, 23 meters | Blue bunting |
| 4 meters, 14 meters, 24 meters | Green and white bunting |
| 5 meters, 15 meters, 25 meters | White bunting |
| 6 meters, 16 meters, 26 meters | Green bunting |
| 7 meters, 17 meters, 27 meters | Red bunting |
| 8 meters, 18 meters, 28 meters | Blue and white bunting |
| 9 meters, 19 meters, 29 meters | Red and white bunting |
| 10 meters | Leather with a hole |
| 20 meters | Leather with a hole and two strips of leather |
| 30 meters | Leather with a hole and three strips of leather |
| Every 0.2 meters | A piece of mackerel line |
- Distances beyond 10 meters would be marked in the same way the first 9 numbers were marked. For example, 11 meters or 21 meters would both be marked with one strip of leather. 14 meters or 24 meters would be marked with green and white bunting.