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Exbal nightforce ballistic program software#
If you specify an altitude and the barometric pressure, the software can use that information to calculate the approximate station pressure, which is what is needed for a ballistic calculation. Most software packages can deal with either station pressure or barometric pressure. Now that you understand the difference between station pressure and barometric pressure, we can deal with finding the pressure. But the actual station pressure is, in fact, less than 20 inches of mercury, which causes some stress in people running the annual Western States 100 footrace in the nearby mountains – a 100 mile ultramarathon at high altitudes. The pressure is reported as if Leadville were at sea level, so that reports of atmospheric pressure of less than 20 inches of mercury won’t send people screaming into the street thinking that they are about to die. That means when the barometric pressure is 29.52 inches of mercury, the station pressure at Leadville is around 19.5 inches of mercury.
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Leadville, Colorado, is situated at just above 10,000 feet. It’s only at altitudes higher than sea level that the difference becomes significant. If you live at or near sea level, as I do much of the year, barometric pressure and station pressure are the same. This is done so that people will have a common reference for the pressure. This is the kind of pressure reported by the National Weather Service and other weather reporting agencies and services. Station pressure for our purposes refers to the absolute atmospheric pressure at the measurement point.īarometric pressure refers to the atmospheric pressure reported as if the reporting station is at sea level, irrespective of its actual altitude, referred to hereafter as SLBP. Ballistic programs usually are programmed to input moisture data as a relative humidity figure.Ītmospheric pressure comes in two flavors, which we will refer to as station pressure and barometric pressure. That means that you the user must specify those quantities to the program. Air density is computed using three inputs: atmospheric pressure, temperature, and the moisture content of the air. In order to calculate the elevation data necessary for accurate shooting, ballistic software must model the density of the air. at a barometric pressure of 29.92 inches of mercury, with zero percent relative humidity. The base condition of the ICAO Standard atmosphere is a temperature of 59 degrees F. What is referred to as “Army Standard Metro Conditions”, used in some ballistic programs, is a BP of 29.53 inches of mercury at a temperature of 59 degrees F.
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The highest pressure recorded in the world was 32.01inches at Agata, USSR, on 31 December, 1968. The lowest BP recorded in the western hemisphere was 26.05 inches of mercury on October 19, 2005, during Hurricane Wilma. In addition, some programs use either inches of mercury or millibars. If local weather data is reported in millibars, it can be converted to inches of mercury by dividing the number of millibars by 1000, then multiplying by 29.53. If the reader is more accustomed to seeing barometric pressure (BP) data expressed in millibars, note that inches of mercury can be converted to millibars by dividing the reading in inches of mercury by 29.53. For the purposes of this article, we will refer to that pressure in inches of mercury. Hurricanes and storms are usually low-pressure systems, while clear weather is usually accompanied by higher pressure. At altitudes where humans can live, barometric pressure decreases approximately at the rate of one inch of mercury per 1000 feet of elevation gain.Īir pressure at the bottom of the column, i.e., the surface of the earth, varies as well, with weather. The earth’s atmosphere is essentially a column of air.Īs you might expect, because of gravity there is more pressure at the bottom of that column than at the top – since the top is essentially a vacuum, i.e., outer space. Barometric Pressure and Ballistic Software Barometric Pressure and Ballistic Software