FACTORS THAT CAUSE TIDES: The tides have their origin in the gravitational forces of the sun and the moon. The earth rotates from west to east and revolves around the sun following an elliptical orbit. Similarly, the moon, rotates from west to east and revolves around, the earth along an elliptical orbit so that the distance between the moon and the earth changes during different times every month. The period of the farthest distance between the moon and the earth is called apogee while the period of the nearest distance is called perigee.
NATURE OF THE TIDES: Thus, two tides and ebbs are experienced twice at every place on the earth's water surface in 24 hours. When the sun, the earth and the moon are in the same line (at the time of full moon and new moon) their gravitational forces work together and high tides are formed.
On the other hand, when the sun and the moon are at the position of right angle with reference to the earth the gravitational forces of the sun and the moon work against each other and hence low tides are formed. This situation occurs during the 8th day of each fortnight of a month.
- Commercial and recreational Navigation through coastal waterways, and within estuaries, bays, and harbours.
- The establishment of chart datums for Hydrography, which are then used for demarcation of a base line or "coastline" for fixing offshore territorial limits, both on the sea surface and on the submerged lands of the Continental Shelf.
- For the furnishing of data useful to fishing, recreational boating, surfing, and a considerable variety of related water sport activities and tourism activities.
- Work on harbour engineering projects, such as the construction of bridges, docks, breakwaters.
- Tidal flows are of importance in navigation, and significant errors in position will occur if they are not taken into account.
- Tidal heights are also important; for example many rivers and harbors have a shallow "bar" at the entrance which will prevent boats with significant draft from entering at certain states of the tide.