HAT meaning in oil and gas

Highest astronomical tide (HAT) is the highest level, and Lowest astronomical tide (LAT) the lowest level that can be expected to occur under average meteorological conditions and under any combination of astronomical conditions. HAT and LAT are not extreme levels, as some meteorological conditions can cause a higher or lower level. The level under these circumstances is known as a 'storm surge' ('negative surge' in the case of level lower than LAT). HAT and LAT are determined by inspecting predicted sea levels over a number of years. Note: The value of HAT and LAT may not be the same in all reference sources. The value given in any source is dependent on the years of inspection, the period which the inspection covered and the exact location and calibration of the tide gauge used