Pressure and Wind
Measuring Tools
Measuring tools are available for pilots to obtain an accurate reading of weather factors.
Units of pressure: millibars (mb), kilopascals (kPa), atmospheres (atm), inches of mercury (inhg)
Anemometer: measures wind speed. Use this to ensure your drone will be able to withstand wind speeds.
Barometer: measures atmospheric pressure by using liquid mercury (North America)
Altimeter: an instrument for determining altitude attained, especially a barometric or radar device used in an aircraft. Must be adjusted based on the area’s pressure in order to ensure an accurate reading.
Image Source: https://www.amazon.ca/Handheld-Anemometer-Instrument-Backlight-Indication/dp/B07X7WMCSP
Image Source: https://sperdirect.com/fr/products/barometer
Image Source: https://www.boldmethod.com/learn-to-fly/systems/how-does-your-aircraft-altimeter-work-in-flight/
Pressure
Wind pressure can cause changes in weather and flying conditions.
Wind shear: Sudden change in wind speed and/or direction. Can be caused by squalls, thunderstorms, being close to large aircraft during land/take off, high rises (wind can be faster between large areas/built up places), wind turbines, large sailboats.
Low pressure: indicates poor weather, hot air rises and cools. High winds.
High pressure: indicates good weather (sunny), cold air moves down and warms. Settled weather.
Pressure gradient map: shows lines that indicate areas of constant pressure. The closer the lines are together, stronger the winds will be in that area.
Image Source: https://www.weatheronline.co.uk/reports/wxfacts/Isobars-on-surface-maps.htm
Altitude
Altitude must be measured in order to avoid accidental crashes and collisions.
Radar altimeter: measures altitude above the terrain presently beneath an aircraft by timing how long it takes a beam of radio waves to travel to ground, reflect, and return to the craft. Does NOT use pressure reading.
ASL: above sea level. Considered true altitude and will be used by Air Traffic Control. Used to avoid air collisions.
AGL: above ground level. Most commonly used in RPAS operation. Can be adjusted to where the mission began if your altitude is higher when you start.
