Chapter 4
Q. 4.5
Given the following information for observed ocean tide levels (semidiurnal) at an established gauge and a new survey site, calculate the sounding datum for the new site.
| Established Gauge 1 (m) | New Site Gauge 2 (m) | |
| LW | 0.5 | 1.2 |
| HW | 3.7 | 3.6 |
| LW | 0.8 | 1.4 |
| HW | 3.6 | 3.3 |
| LW | 0.4 | 1.0 |
| HW | 3.9 | 3.9 |
| LW | 0.7 | 1.3 |
| MHWS | 3.5 | – |
| MLWS | 0.5 | – |
Step-by-Step
Verified Solution
Following the steps outlined in the section above:
(OMLW)_{1} = (0.5 + 3 × 0.8 + 3 × 0.4 + 0.7)/8 = 0.51
(OMHW)_{1} = (3.7 + 2 × 3.6 + 3.9)/4 = 3.70
(OMR)_{1} = 3.70 − 0.51 = 3.19
(OMTL)_{1} = (3.70 + 0.51)/2 = 2.10
(TMTL)_{1} = (3.5 + 0.5)/2 = 2.00
(OMLW)_{2} = (1.2 + 3 × 1.4 + 3 × 1.0 + 1.3)/8 = 1.21
(OMHW)_{2} = (3.6 + 2 × 3.3 + 3.9)/4 = 3.52
(OMR)_{2} = 2.31
(OMTL)_{2} = 2.36
The correct sounding datum at the new site should be
2.36 − (2.10 − 2.0) − (2.0 × 2.31)/3.19 = 0.81 m.
Had (TMTL)_{1} been unknown the next best estimate would have been
2.36 − (2.10 × 2.31)/3.19 = 0.84 m.