Sea level the warmer water expands. For at least the last 100 years, sea level has been rising at an average rate of about per year. Most of this rise can be attributed to the increase in temperature of the sea and the resulting slight thermal expansion of the upper of sea water. Additional contributions, as much as one-quarter of the total, come from water sources on land, such as melting snow and glaciers and extraction of groundwater for irrigation and other agricultural and human uses. Pilots can estimate height above sea level with an altimeter set to a defined barometric pressure.
Earth bulge hand, k < 1 means a shorter service range. Experience has shown that, under normal weather conditions k is 4/3. That means that, the maximum service range increases by 15%. for h in m. and d in km. for h in ft. and d in miles ; But in stormy weather, k may decrease to cause fading in transmission. (In extreme cases k can be less than 1.) That is equivalent to a hypothetical decrease in Earth radius and an increase of Earth bulge. In normal weather conditions, the service range of a transmitting station at an altitude of 1500