# Calculated Tide of a Secondary Port (Overhead Power Cable)

## Calculated Tide of a Secondary Port (Overhead Power Cable)

Charted clearance of an overhead power cable is 62.3 meters above MHWS at Bournemouth (ATT Vol. 1, 37) What will be the clearance of the ship’s mast while passing the cable at 0930 hrs GMT on 20th Nov? Assuming the mast height was 57.8 meters from the ship’s keel and the ship’s draft was 9.4m at that time.

*** (Note: at the below part in this page, interpolation methods has been done)

Bournemouth is a secondary port and PORTSMOUTH is a standard port. At first, we have to extract data for interpolation.

## Calculated Tide of a Secondary Port (Overhead Power Cable)

Our required time is 0930 hrs GMT on 20th Nov, Now read the data in the daily pages of the standard port.

Use format

Use the tidal graph

MHWS in Portsmouth: 4.7 m
Ht Diff for Bournemouth: -2.7 m
MHWS at Bournemouth: 2 m
Height of tide at 0930 Z: 1.6 m (at Bournemouth)
Tidal Ht less: 0.4 m
Ht of overhead cable from MHWS: 62.3 m
Total ht of overhead cable: 62.7 m
Overhead clearance: 62.7 – (57.8 – 9.4) = 14.3 m