Rules
The following rules are applied by UKHO for sounding rounding:
• Soundings 30 metres or deeper: If the decimal part is .0750, round up to the next whole metre.
• Soundings between 21 metres and 29.999 metres: If the decimal part is 0.5 or greater, round down to 0.5 Soundings between 0 metres and 20.999 metres: If the decimal part is 0.80 and deeper, round up by 0.1.
• Drying heights from -0.001 to -20.999 metres: If the decimal part is greater than 0.030, round down by 0.1.
• Drying heights from -21 to -29.999: If the decimal part is greater than 0.5, round up by 0.5.
• Drying heights from -30: If the decimal part is greater than 0.750, round up by 1.0.
Range | Level | Shallowest | Deepest | Direction | Result |
|---|---|---|---|---|---|
0.000 to 20.999 | x.1 | x.y00 | x.y79 | Shallower | x.y |
x.1 | x.y80 | x.y99 | Deeper | x.(y+.1) | |
21.000 to 29.999 | x.5 | x.000 | x.499 | Shallower | x.000 |
x.5 | x.500 | x.999 | Shallower | x.500 | |
30.000 and deeper | x | x.000 | x.749 | Shallower | x.000 |
x | x.750 | x.999 | Deeper | x+1 | |
-20.999 to –0.001 | x.1 | -x.y29 | -x.y00 | Deeper | -x.y |
x.1 | -x.y99 | -x.y30 | Shallower | -x.(y-.1) | |
-29.999 to –21.000 | x.5 | -x.499 | -x.000 | Shallower | -x.5 |
x.5 | -x.999 | -x.500 | Shallower | -x-1 | |
-30.000 and Shallower | x | -x.749 | -x.000 | Deeper | -x.000 |
x | -x.999 | -x.750 | Shallower | -x-1 |
Sounding Example
0.1 Level | 0.5 Level | 1.0 Level | |||
|---|---|---|---|---|---|
Depth (m) | Display (m) | Depth (m) | Display (m) | Depth (m) | Display (m) |
0.000 | 0 | 21.000 | 21 | 30.000 | 30 |
0.001 | 0 | 21.499 | 21 | 30.749 | 30 |
0.008 | 0 | 21.500 | 21.5 | 30.750 | 31 |
0.009 | 0 | 21.999 | 21.5 | 30.999 | 31 |
0.010 | 0 | 29.000 | 29 | 31.000 | 31 |
0.079 | 0 | 29.499 | 29 | 31.749 | 31 |
0.080 | 0.1 | 29.500 | 29.5 | 31.750 | 32 |
0.099 | 0.1 | 29.999 | 29.5 | 31.999 | 32 |
0.100 | 0.1 | ||||
0.179 | 0.1 | ||||
0.180 | 0.2 | ||||
0.199 | 0.2 | ||||
0.900 | 0.9 | ||||
0.979 | 0.9 | ||||
0.980 | 1 | ||||
0.999 | 1 | ||||
20.900 | 20.9 | ||||
20.979 | 20.9 | ||||
20.980 | 21 | ||||
20.999 | 21 | ||||
Drying Heights Example
Depth (m) | Display (m) |
|---|---|
-0.999 | -1 |
-0.930 | -1 |
-0.929 | -0.9 |
-0.900 | -0.9 |
-0.199 | -0.2 |
-0.130 | -0.2 |
-0.129 | -0.1 |
-0.099 | -0.1 |
-0.030 | -0.1 |
-0.029 | 0 |
-0.010 | 0 |
-0.009 | 0 |